Series comparison

-[PULL for-7.0 0/2] Block patches
+[PULL 0/3] Block patches
-The following changes since commit 15ef89d2a1a7b93845a6b09c2ee8e1979f6eb30b:
+The following changes since commit 9cf289af47bcfae5c75de37d8e5d6fd23705322c:
-  Update version for v7.0.0-rc1 release (2022-03-22 22:58:44 +0000)
+  Merge tag 'qga-pull-request' of gitlab.com:marcandre.lureau/qemu into staging (2022-05-04 03:42:49 -0700)
 are available in the Git repository at:
   https://gitlab.com/stefanha/qemu.git tags/block-pull-request
-for you to fetch changes up to 2539eade4f689eda7e9fe45486f18334bfbafaf0:
+for you to fetch changes up to bef2e050d6a7feb865854c65570c496ac5a8cf53:
-  hw: Fix misleading hexadecimal format (2022-03-24 10:38:42 +0000)
+  util/event-loop-base: Introduce options to set the thread pool size (2022-05-04 17:02:19 +0100)
 ----------------------------------------------------------------
 Pull request
-Philippe found cases where the 0x%d format string was used, leading to
+Add new thread-pool-min/thread-pool-max parameters to control the thread pool
-misleading output. The patches look harmless and could save people time, so I
+used for async I/O.
 think it's worth including them in 7.0.
 ----------------------------------------------------------------
-Philippe Mathieu-Daudé (2):
+Nicolas Saenz Julienne (3):
-  block: Fix misleading hexadecimal format
+  Introduce event-loop-base abstract class
-  hw: Fix misleading hexadecimal format
+  util/main-loop: Introduce the main loop into QOM
   util/event-loop-base: Introduce options to set the thread pool size
- block/parallels-ext.c | 2 +-
+ qapi/qom.json                    |  43 ++++++++--
- hw/i386/sgx.c         | 2 +-
+ meson.build                      |  26 +++---
- hw/i386/trace-events  | 6 +++---
+ include/block/aio.h              |  10 +++
- hw/misc/trace-events  | 4 ++--
+ include/block/thread-pool.h      |   3 +
- hw/scsi/trace-events  | 4 ++--
+ include/qemu/main-loop.h         |  10 +++
-files changed, 9 insertions(+), 9 deletions(-)
+ include/sysemu/event-loop-base.h |  41 +++++++++
  include/sysemu/iothread.h        |   6 +-
  event-loop-base.c                | 140 +++++++++++++++++++++++++++++++
  iothread.c                       |  68 +++++----------
  util/aio-posix.c                 |   1 +
  util/async.c                     |  20 +++++
  util/main-loop.c                 |  65 ++++++++++++++
  util/thread-pool.c               |  55 +++++++++++-
 files changed, 419 insertions(+), 69 deletions(-)
  create mode 100644 include/sysemu/event-loop-base.h
  create mode 100644 event-loop-base.c
 --
 .35.1

-[PULL for-7.0 2/2] hw: Fix misleading hexadecimal format
+[PULL 1/3] Introduce event-loop-base abstract class
-From: Philippe Mathieu-Daudé <f4bug@amsat.org>
+From: Nicolas Saenz Julienne <nsaenzju@redhat.com>
-"0x%u" format is very misleading, replace by "0x%x".
+Introduce the 'event-loop-base' abstract class, it'll hold the
+properties common to all event loops and provide the necessary hooks for
-Found running:
+their creation and maintenance. Then have iothread inherit from it.
-  $ git grep -E '0x%[0-9]*([lL]*|" ?PRI)[dDuU]' hw/
+EventLoopBaseClass is defined as user creatable and provides a hook for
+its children to attach themselves to the user creatable class 'complete'
-Inspired-by: Richard Henderson <richard.henderson@linaro.org>
+function. It also provides an update_params() callback to propagate
-Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
+property changes onto its children.
-Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
-Message-id: 20220323114718.58714-3-philippe.mathieu.daude@gmail.com
+The new 'event-loop-base' class will live in the root directory. It is
 built on its own using the 'link_whole' option (there are no direct
 function dependencies between the class and its children, it all happens
 trough 'constructor' magic). And also imposes new compilation
 dependencies:
     qom <- event-loop-base <- blockdev (iothread.c)
 And in subsequent patches:
     qom <- event-loop-base <- qemuutil (util/main-loop.c)
 All this forced some amount of reordering in meson.build:
  - Moved qom build definition before qemuutil. Doing it the other way
    around (i.e. moving qemuutil after qom) isn't possible as a lot of
    core libraries that live in between the two depend on it.
  - Process the 'hw' subdir earlier, as it introduces files into the
    'qom' source set.
 No functional changes intended.
 Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
 Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
 Acked-by: Markus Armbruster <armbru@redhat.com>
 Message-id: 20220425075723.20019-2-nsaenzju@redhat.com
 Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
 ---
- hw/i386/sgx.c        | 2 +-
+ qapi/qom.json                    |  22 +++++--
- hw/i386/trace-events | 6 +++---
+ meson.build                      |  23 ++++---
- hw/misc/trace-events | 4 ++--
+ include/sysemu/event-loop-base.h |  36 +++++++++++
- hw/scsi/trace-events | 4 ++--
+ include/sysemu/iothread.h        |   6 +-
-files changed, 8 insertions(+), 8 deletions(-)
+ event-loop-base.c                | 104 +++++++++++++++++++++++++++++++
+ iothread.c                       |  65 ++++++-------------
-diff --git a/hw/i386/sgx.c b/hw/i386/sgx.c
+files changed, 192 insertions(+), 64 deletions(-)
  create mode 100644 include/sysemu/event-loop-base.h
  create mode 100644 event-loop-base.c
 diff --git a/qapi/qom.json b/qapi/qom.json
 index XXXXXXX..XXXXXXX 100644
---- a/hw/i386/sgx.c
+--- a/qapi/qom.json
-+++ b/hw/i386/sgx.c
++++ b/qapi/qom.json
-@@ -XXX,XX +XXX,XX @@ void pc_machine_init_sgx_epc(PCMachineState *pcms)
+@@ -XXX,XX +XXX,XX @@
              '*repeat': 'bool',
              '*grab-toggle': 'GrabToggleKeys' } }
 +##
 +# @EventLoopBaseProperties:
 +#
 +# Common properties for event loops
 +#
 +# @aio-max-batch: maximum number of requests in a batch for the AIO engine,
 +#                 0 means that the engine will use its default.
 +#                 (default: 0)
 +#
 +# Since: 7.1
 +##
 +{ 'struct': 'EventLoopBaseProperties',
 +  'data': { '*aio-max-batch': 'int' } }
 +
  ##
  # @IothreadProperties:
  #
@@ -XXX,XX +XXX,XX @@
  #               algorithm detects it is spending too long polling without
  #               encountering events. 0 selects a default behaviour (default: 0)
  #
 -# @aio-max-batch: maximum number of requests in a batch for the AIO engine,
 -#                 0 means that the engine will use its default
 -#                 (default:0, since 6.1)
 +# The @aio-max-batch option is available since 6.1.
  #
  # Since: 2.0
  ##
  { 'struct': 'IothreadProperties',
 +  'base': 'EventLoopBaseProperties',
    'data': { '*poll-max-ns': 'int',
              '*poll-grow': 'int',
 -            '*poll-shrink': 'int',
 -            '*aio-max-batch': 'int' } }
 +            '*poll-shrink': 'int' } }
  ##
  # @MemoryBackendProperties:
 diff --git a/meson.build b/meson.build
 index XXXXXXX..XXXXXXX 100644
 --- a/meson.build
 +++ b/meson.build
@@ -XXX,XX +XXX,XX @@ subdir('qom')
  subdir('authz')
  subdir('crypto')
  subdir('ui')
 +subdir('hw')
  if enable_modules
@@ -XXX,XX +XXX,XX @@ if enable_modules
    modulecommon = declare_dependency(link_whole: libmodulecommon, compile_args: '-DBUILD_DSO')
  endif
 +qom_ss = qom_ss.apply(config_host, strict: false)
 +libqom = static_library('qom', qom_ss.sources() + genh,
 +                        dependencies: [qom_ss.dependencies()],
 +                        name_suffix: 'fa')
 +qom = declare_dependency(link_whole: libqom)
 +
 +event_loop_base = files('event-loop-base.c')
 +event_loop_base = static_library('event-loop-base', sources: event_loop_base + genh,
 +                                 build_by_default: true)
 +event_loop_base = declare_dependency(link_whole: event_loop_base,
 +                                     dependencies: [qom])
 +
  stub_ss = stub_ss.apply(config_all, strict: false)
  util_ss.add_all(trace_ss)
@@ -XXX,XX +XXX,XX @@ subdir('monitor')
  subdir('net')
  subdir('replay')
  subdir('semihosting')
 -subdir('hw')
  subdir('tcg')
  subdir('fpu')
  subdir('accel')
@@ -XXX,XX +XXX,XX @@ qemu_syms = custom_target('qemu.syms', output: 'qemu.syms',
                               capture: true,
                               command: [undefsym, nm, '@INPUT@'])
 -qom_ss = qom_ss.apply(config_host, strict: false)
 -libqom = static_library('qom', qom_ss.sources() + genh,
 -                        dependencies: [qom_ss.dependencies()],
 -                        name_suffix: 'fa')
 -
 -qom = declare_dependency(link_whole: libqom)
 -
  authz_ss = authz_ss.apply(config_host, strict: false)
  libauthz = static_library('authz', authz_ss.sources() + genh,
                            dependencies: [authz_ss.dependencies()],
@@ -XXX,XX +XXX,XX @@ libblockdev = static_library('blockdev', blockdev_ss.sources() + genh,
                               build_by_default: false)
  blockdev = declare_dependency(link_whole: [libblockdev],
 -                              dependencies: [block])
 +                              dependencies: [block, event_loop_base])
  qmp_ss = qmp_ss.apply(config_host, strict: false)
  libqmp = static_library('qmp', qmp_ss.sources() + genh,
 diff --git a/include/sysemu/event-loop-base.h b/include/sysemu/event-loop-base.h
 new file mode 100644
 index XXXXXXX..XXXXXXX
 --- /dev/null
 +++ b/include/sysemu/event-loop-base.h
@@ -XXX,XX +XXX,XX @@
 +/*
 + * QEMU event-loop backend
 + *
 + * Copyright (C) 2022 Red Hat Inc
 + *
 + * Authors:
 + *  Nicolas Saenz Julienne <nsaenzju@redhat.com>
 + *
 + * This work is licensed under the terms of the GNU GPL, version 2 or later.
 + * See the COPYING file in the top-level directory.
 + */
 +#ifndef QEMU_EVENT_LOOP_BASE_H
 +#define QEMU_EVENT_LOOP_BASE_H
 +
 +#include "qom/object.h"
 +#include "block/aio.h"
 +#include "qemu/typedefs.h"
 +
 +#define TYPE_EVENT_LOOP_BASE         "event-loop-base"
 +OBJECT_DECLARE_TYPE(EventLoopBase, EventLoopBaseClass,
 +                    EVENT_LOOP_BASE)
 +
 +struct EventLoopBaseClass {
 +    ObjectClass parent_class;
 +
 +    void (*init)(EventLoopBase *base, Error **errp);
 +    void (*update_params)(EventLoopBase *base, Error **errp);
 +};
 +
 +struct EventLoopBase {
 +    Object parent;
 +
 +    /* AioContext AIO engine parameters */
 +    int64_t aio_max_batch;
 +};
 +#endif
 diff --git a/include/sysemu/iothread.h b/include/sysemu/iothread.h
 index XXXXXXX..XXXXXXX 100644
 --- a/include/sysemu/iothread.h
 +++ b/include/sysemu/iothread.h
@@ -XXX,XX +XXX,XX @@
  #include "block/aio.h"
  #include "qemu/thread.h"
  #include "qom/object.h"
 +#include "sysemu/event-loop-base.h"
  #define TYPE_IOTHREAD "iothread"
  struct IOThread {
 -    Object parent_obj;
 +    EventLoopBase parent_obj;
      QemuThread thread;
      AioContext *ctx;
@@ -XXX,XX +XXX,XX @@ struct IOThread {
      int64_t poll_max_ns;
      int64_t poll_grow;
      int64_t poll_shrink;
 -
 -    /* AioContext AIO engine parameters */
 -    int64_t aio_max_batch;
  };
  typedef struct IOThread IOThread;
 diff --git a/event-loop-base.c b/event-loop-base.c
 new file mode 100644
 index XXXXXXX..XXXXXXX
 --- /dev/null
 +++ b/event-loop-base.c
@@ -XXX,XX +XXX,XX @@
 +/*
 + * QEMU event-loop base
 + *
 + * Copyright (C) 2022 Red Hat Inc
 + *
 + * Authors:
 + *  Stefan Hajnoczi <stefanha@redhat.com>
 + *  Nicolas Saenz Julienne <nsaenzju@redhat.com>
 + *
 + * This work is licensed under the terms of the GNU GPL, version 2 or later.
 + * See the COPYING file in the top-level directory.
 + */
 +
 +#include "qemu/osdep.h"
 +#include "qom/object_interfaces.h"
 +#include "qapi/error.h"
 +#include "sysemu/event-loop-base.h"
 +
 +typedef struct {
 +    const char *name;
 +    ptrdiff_t offset; /* field's byte offset in EventLoopBase struct */
 +} EventLoopBaseParamInfo;
 +
 +static EventLoopBaseParamInfo aio_max_batch_info = {
 +    "aio-max-batch", offsetof(EventLoopBase, aio_max_batch),
 +};
 +
 +static void event_loop_base_get_param(Object *obj, Visitor *v,
 +        const char *name, void *opaque, Error **errp)
 +{
 +    EventLoopBase *event_loop_base = EVENT_LOOP_BASE(obj);
 +    EventLoopBaseParamInfo *info = opaque;
 +    int64_t *field = (void *)event_loop_base + info->offset;
 +
 +    visit_type_int64(v, name, field, errp);
 +}
 +
 +static void event_loop_base_set_param(Object *obj, Visitor *v,
 +        const char *name, void *opaque, Error **errp)
 +{
 +    EventLoopBaseClass *bc = EVENT_LOOP_BASE_GET_CLASS(obj);
 +    EventLoopBase *base = EVENT_LOOP_BASE(obj);
 +    EventLoopBaseParamInfo *info = opaque;
 +    int64_t *field = (void *)base + info->offset;
 +    int64_t value;
 +
 +    if (!visit_type_int64(v, name, &value, errp)) {
 +        return;
 +    }
 +
 +    if (value < 0) {
 +        error_setg(errp, "%s value must be in range [0, %" PRId64 "]",
 +                   info->name, INT64_MAX);
 +        return;
 +    }
 +
 +    *field = value;
 +
 +    if (bc->update_params) {
 +        bc->update_params(base, errp);
 +    }
 +
 +    return;
 +}
 +
 +static void event_loop_base_complete(UserCreatable *uc, Error **errp)
 +{
 +    EventLoopBaseClass *bc = EVENT_LOOP_BASE_GET_CLASS(uc);
 +    EventLoopBase *base = EVENT_LOOP_BASE(uc);
 +
 +    if (bc->init) {
 +        bc->init(base, errp);
 +    }
 +}
 +
 +static void event_loop_base_class_init(ObjectClass *klass, void *class_data)
 +{
 +    UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
 +    ucc->complete = event_loop_base_complete;
 +
 +    object_class_property_add(klass, "aio-max-batch", "int",
 +                              event_loop_base_get_param,
 +                              event_loop_base_set_param,
 +                              NULL, &aio_max_batch_info);
 +}
 +
 +static const TypeInfo event_loop_base_info = {
 +    .name = TYPE_EVENT_LOOP_BASE,
 +    .parent = TYPE_OBJECT,
 +    .instance_size = sizeof(EventLoopBase),
 +    .class_size = sizeof(EventLoopBaseClass),
 +    .class_init = event_loop_base_class_init,
 +    .abstract = true,
 +    .interfaces = (InterfaceInfo[]) {
 +        { TYPE_USER_CREATABLE },
 +        { }
 +    }
 +};
 +
 +static void register_types(void)
 +{
 +    type_register_static(&event_loop_base_info);
 +}
 +type_init(register_types);
 diff --git a/iothread.c b/iothread.c
 index XXXXXXX..XXXXXXX 100644
 --- a/iothread.c
 +++ b/iothread.c
@@ -XXX,XX +XXX,XX @@
  #include "qemu/module.h"
  #include "block/aio.h"
  #include "block/block.h"
 +#include "sysemu/event-loop-base.h"
  #include "sysemu/iothread.h"
  #include "qapi/error.h"
  #include "qapi/qapi-commands-misc.h"
@@ -XXX,XX +XXX,XX @@ static void iothread_init_gcontext(IOThread *iothread)
      iothread->main_loop = g_main_loop_new(iothread->worker_context, TRUE);
  }
 -static void iothread_set_aio_context_params(IOThread *iothread, Error **errp)
 +static void iothread_set_aio_context_params(EventLoopBase *base, Error **errp)
  {
 +    IOThread *iothread = IOTHREAD(base);
      ERRP_GUARD();
 +    if (!iothread->ctx) {
 +        return;
 +    }
 +
      aio_context_set_poll_params(iothread->ctx,
                                  iothread->poll_max_ns,
                                  iothread->poll_grow,
@@ -XXX,XX +XXX,XX @@ static void iothread_set_aio_context_params(IOThread *iothread, Error **errp)
      }
-     if ((sgx_epc->base + sgx_epc->size) < sgx_epc->base) {
+     aio_context_set_aio_params(iothread->ctx,
--        error_report("Size of all 'sgx-epc' =0x%"PRIu64" causes EPC to wrap",
+-                               iothread->aio_max_batch,
-+        error_report("Size of all 'sgx-epc' =0x%"PRIx64" causes EPC to wrap",
++                               iothread->parent_obj.aio_max_batch,
-                      sgx_epc->size);
+                                errp);
-         exit(EXIT_FAILURE);
+ }
 -static void iothread_complete(UserCreatable *obj, Error **errp)
 +
 +static void iothread_init(EventLoopBase *base, Error **errp)
  {
      Error *local_error = NULL;
 -    IOThread *iothread = IOTHREAD(obj);
 +    IOThread *iothread = IOTHREAD(base);
      char *thread_name;
      iothread->stopping = false;
@@ -XXX,XX +XXX,XX @@ static void iothread_complete(UserCreatable *obj, Error **errp)
       */
      iothread_init_gcontext(iothread);
 -    iothread_set_aio_context_params(iothread, &local_error);
 +    iothread_set_aio_context_params(base, &local_error);
      if (local_error) {
          error_propagate(errp, local_error);
          aio_context_unref(iothread->ctx);
@@ -XXX,XX +XXX,XX @@ static void iothread_complete(UserCreatable *obj, Error **errp)
       * to inherit.
       */
      thread_name = g_strdup_printf("IO %s",
 -                        object_get_canonical_path_component(OBJECT(obj)));
 +                        object_get_canonical_path_component(OBJECT(base)));
      qemu_thread_create(&iothread->thread, thread_name, iothread_run,
                         iothread, QEMU_THREAD_JOINABLE);
      g_free(thread_name);
@@ -XXX,XX +XXX,XX @@ static IOThreadParamInfo poll_grow_info = {
  static IOThreadParamInfo poll_shrink_info = {
      "poll-shrink", offsetof(IOThread, poll_shrink),
  };
 -static IOThreadParamInfo aio_max_batch_info = {
 -    "aio-max-batch", offsetof(IOThread, aio_max_batch),
 -};
  static void iothread_get_param(Object *obj, Visitor *v,
          const char *name, IOThreadParamInfo *info, Error **errp)
@@ -XXX,XX +XXX,XX @@ static void iothread_set_poll_param(Object *obj, Visitor *v,
      }
-diff --git a/hw/i386/trace-events b/hw/i386/trace-events
+ }
-index XXXXXXX..XXXXXXX 100644
---- a/hw/i386/trace-events
+-static void iothread_get_aio_param(Object *obj, Visitor *v,
-+++ b/hw/i386/trace-events
+-        const char *name, void *opaque, Error **errp)
-@@ -XXX,XX +XXX,XX @@ vtd_fault_disabled(void) "Fault processing disabled for context entry"
+-{
- vtd_replay_ce_valid(const char *mode, uint8_t bus, uint8_t dev, uint8_t fn, uint16_t domain, uint64_t hi, uint64_t lo) "%s: replay valid context device %02"PRIx8":%02"PRIx8".%02"PRIx8" domain 0x%"PRIx16" hi 0x%"PRIx64" lo 0x%"PRIx64
+-    IOThreadParamInfo *info = opaque;
- vtd_replay_ce_invalid(uint8_t bus, uint8_t dev, uint8_t fn) "replay invalid context device %02"PRIx8":%02"PRIx8".%02"PRIx8
+-
- vtd_page_walk_level(uint64_t addr, uint32_t level, uint64_t start, uint64_t end) "walk (base=0x%"PRIx64", level=%"PRIu32") iova range 0x%"PRIx64" - 0x%"PRIx64
+-    iothread_get_param(obj, v, name, info, errp);
--vtd_page_walk_one(uint16_t domain, uint64_t iova, uint64_t gpa, uint64_t mask, int perm) "domain 0x%"PRIu16" iova 0x%"PRIx64" -> gpa 0x%"PRIx64" mask 0x%"PRIx64" perm %d"
+-}
-+vtd_page_walk_one(uint16_t domain, uint64_t iova, uint64_t gpa, uint64_t mask, int perm) "domain 0x%"PRIx16" iova 0x%"PRIx64" -> gpa 0x%"PRIx64" mask 0x%"PRIx64" perm %d"
+-
- vtd_page_walk_one_skip_map(uint64_t iova, uint64_t mask, uint64_t translated) "iova 0x%"PRIx64" mask 0x%"PRIx64" translated 0x%"PRIx64
+-static void iothread_set_aio_param(Object *obj, Visitor *v,
- vtd_page_walk_one_skip_unmap(uint64_t iova, uint64_t mask) "iova 0x%"PRIx64" mask 0x%"PRIx64
+-        const char *name, void *opaque, Error **errp)
- vtd_page_walk_skip_read(uint64_t iova, uint64_t next) "Page walk skip iova 0x%"PRIx64" - 0x%"PRIx64" due to unable to read"
+-{
- vtd_page_walk_skip_reserve(uint64_t iova, uint64_t next) "Page walk skip iova 0x%"PRIx64" - 0x%"PRIx64" due to rsrv set"
+-    IOThread *iothread = IOTHREAD(obj);
- vtd_switch_address_space(uint8_t bus, uint8_t slot, uint8_t fn, bool on) "Device %02x:%02x.%x switching address space (iommu enabled=%d)"
+-    IOThreadParamInfo *info = opaque;
- vtd_as_unmap_whole(uint8_t bus, uint8_t slot, uint8_t fn, uint64_t iova, uint64_t size) "Device %02x:%02x.%x start 0x%"PRIx64" size 0x%"PRIx64
+-
--vtd_translate_pt(uint16_t sid, uint64_t addr) "source id 0x%"PRIu16", iova 0x%"PRIx64
+-    if (!iothread_set_param(obj, v, name, info, errp)) {
--vtd_pt_enable_fast_path(uint16_t sid, bool success) "sid 0x%"PRIu16" %d"
+-        return;
-+vtd_translate_pt(uint16_t sid, uint64_t addr) "source id 0x%"PRIx16", iova 0x%"PRIx64
+-    }
-+vtd_pt_enable_fast_path(uint16_t sid, bool success) "sid 0x%"PRIx16" %d"
+-
- vtd_irq_generate(uint64_t addr, uint64_t data) "addr 0x%"PRIx64" data 0x%"PRIx64
+-    if (iothread->ctx) {
- vtd_reg_read(uint64_t addr, uint64_t size) "addr 0x%"PRIx64" size 0x%"PRIx64
+-        aio_context_set_aio_params(iothread->ctx,
- vtd_reg_write(uint64_t addr, uint64_t size, uint64_t val) "addr 0x%"PRIx64" size 0x%"PRIx64" value 0x%"PRIx64
+-                                   iothread->aio_max_batch,
-diff --git a/hw/misc/trace-events b/hw/misc/trace-events
+-                                   errp);
-index XXXXXXX..XXXXXXX 100644
+-    }
---- a/hw/misc/trace-events
+-}
-+++ b/hw/misc/trace-events
+-
-@@ -XXX,XX +XXX,XX @@
+ static void iothread_class_init(ObjectClass *klass, void *class_data)
- # See docs/devel/tracing.rst for syntax documentation.
+ {
+-    UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
- # allwinner-cpucfg.c
+-    ucc->complete = iothread_complete;
--allwinner_cpucfg_cpu_reset(uint8_t cpu_id, uint32_t reset_addr) "id %u, reset_addr 0x%" PRIu32
++    EventLoopBaseClass *bc = EVENT_LOOP_BASE_CLASS(klass);
-+allwinner_cpucfg_cpu_reset(uint8_t cpu_id, uint32_t reset_addr) "id %u, reset_addr 0x%" PRIx32
++
- allwinner_cpucfg_read(uint64_t offset, uint64_t data, unsigned size) "offset 0x%" PRIx64 " data 0x%" PRIx64 " size %" PRIu32
++    bc->init = iothread_init;
- allwinner_cpucfg_write(uint64_t offset, uint64_t data, unsigned size) "offset 0x%" PRIx64 " data 0x%" PRIx64 " size %" PRIu32
++    bc->update_params = iothread_set_aio_context_params;
-@@ -XXX,XX +XXX,XX @@ imx7_gpr_write(uint64_t offset, uint64_t value) "addr 0x%08" PRIx64 "value 0x%08
+     object_class_property_add(klass, "poll-max-ns", "int",
+                               iothread_get_poll_param,
- # mos6522.c
+@@ -XXX,XX +XXX,XX @@ static void iothread_class_init(ObjectClass *klass, void *class_data)
- mos6522_set_counter(int index, unsigned int val) "T%d.counter=%d"
+                               iothread_get_poll_param,
--mos6522_get_next_irq_time(uint16_t latch, int64_t d, int64_t delta) "latch=%d counter=0x%"PRId64 " delta_next=0x%"PRId64
+                               iothread_set_poll_param,
-+mos6522_get_next_irq_time(uint16_t latch, int64_t d, int64_t delta) "latch=%d counter=0x%"PRIx64 " delta_next=0x%"PRIx64
+                               NULL, &poll_shrink_info);
- mos6522_set_sr_int(void) "set sr_int"
+-    object_class_property_add(klass, "aio-max-batch", "int",
- mos6522_write(uint64_t addr, const char *name, uint64_t val) "reg=0x%"PRIx64 " [%s] val=0x%"PRIx64
+-                              iothread_get_aio_param,
- mos6522_read(uint64_t addr, const char *name, unsigned val) "reg=0x%"PRIx64 " [%s] val=0x%x"
+-                              iothread_set_aio_param,
-diff --git a/hw/scsi/trace-events b/hw/scsi/trace-events
+-                              NULL, &aio_max_batch_info);
-index XXXXXXX..XXXXXXX 100644
+ }
---- a/hw/scsi/trace-events
-+++ b/hw/scsi/trace-events
+ static const TypeInfo iothread_info = {
-@@ -XXX,XX +XXX,XX @@ lsi_bad_phase_interrupt(void) "Phase mismatch interrupt"
+     .name = TYPE_IOTHREAD,
- lsi_bad_selection(uint32_t id) "Selected absent target %"PRIu32
+-    .parent = TYPE_OBJECT,
- lsi_do_dma_unavailable(void) "DMA no data available"
++    .parent = TYPE_EVENT_LOOP_BASE,
- lsi_do_dma(uint64_t addr, int len) "DMA addr=0x%"PRIx64" len=%d"
+     .class_init = iothread_class_init,
--lsi_queue_command(uint32_t tag) "Queueing tag=0x%"PRId32
+     .instance_size = sizeof(IOThread),
-+lsi_queue_command(uint32_t tag) "Queueing tag=0x%"PRIx32
+     .instance_init = iothread_instance_init,
- lsi_add_msg_byte_error(void) "MSG IN data too long"
+     .instance_finalize = iothread_instance_finalize,
- lsi_add_msg_byte(uint8_t data) "MSG IN 0x%02x"
+-    .interfaces = (InterfaceInfo[]) {
- lsi_reselect(int id) "Reselected target %d"
+-        {TYPE_USER_CREATABLE},
-@@ -XXX,XX +XXX,XX @@ lsi_do_msgout_noop(void) "MSG: No Operation"
+-        {}
- lsi_do_msgout_extended(uint8_t msg, uint8_t len) "Extended message 0x%x (len %d)"
+-    },
- lsi_do_msgout_ignored(const char *msg) "%s (ignored)"
+ };
- lsi_do_msgout_simplequeue(uint8_t select_tag) "SIMPLE queue tag=0x%x"
--lsi_do_msgout_abort(uint32_t tag) "MSG: ABORT TAG tag=0x%"PRId32
+ static void iothread_register_types(void)
-+lsi_do_msgout_abort(uint32_t tag) "MSG: ABORT TAG tag=0x%"PRIx32
+@@ -XXX,XX +XXX,XX @@ static int query_one_iothread(Object *object, void *opaque)
- lsi_do_msgout_clearqueue(uint32_t tag) "MSG: CLEAR QUEUE tag=0x%"PRIx32
+     info->poll_max_ns = iothread->poll_max_ns;
- lsi_do_msgout_busdevicereset(uint32_t tag) "MSG: BUS DEVICE RESET tag=0x%"PRIx32
+     info->poll_grow = iothread->poll_grow;
- lsi_do_msgout_select(int id) "Select LUN %d"
+     info->poll_shrink = iothread->poll_shrink;
 -    info->aio_max_batch = iothread->aio_max_batch;
 +    info->aio_max_batch = iothread->parent_obj.aio_max_batch;
      QAPI_LIST_APPEND(*tail, info);
      return 0;
 --
 .35.1

-New patch
+[PULL 2/3] util/main-loop: Introduce the main loop into QOM
+From: Nicolas Saenz Julienne <nsaenzju@redhat.com>
 'event-loop-base' provides basic property handling for all 'AioContext'
 based event loops. So let's define a new 'MainLoopClass' that inherits
 from it. This will permit tweaking the main loop's properties through
 qapi as well as through the command line using the '-object' keyword[1].
 Only one instance of 'MainLoopClass' might be created at any time.
 'EventLoopBaseClass' learns a new callback, 'can_be_deleted()' so as to
 mark 'MainLoop' as non-deletable.
 [1] For example:
       -object main-loop,id=main-loop,aio-max-batch=<value>
 Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
 Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
 Acked-by: Markus Armbruster <armbru@redhat.com>
 Message-id: 20220425075723.20019-3-nsaenzju@redhat.com
 Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
 ---
  qapi/qom.json                    | 13 ++++++++
  meson.build                      |  3 +-
  include/qemu/main-loop.h         | 10 ++++++
  include/sysemu/event-loop-base.h |  1 +
  event-loop-base.c                | 13 ++++++++
  util/main-loop.c                 | 56 ++++++++++++++++++++++++++++++++
 files changed, 95 insertions(+), 1 deletion(-)
 diff --git a/qapi/qom.json b/qapi/qom.json
 index XXXXXXX..XXXXXXX 100644
 --- a/qapi/qom.json
 +++ b/qapi/qom.json
@@ -XXX,XX +XXX,XX @@
              '*poll-grow': 'int',
              '*poll-shrink': 'int' } }
 +##
 +# @MainLoopProperties:
 +#
 +# Properties for the main-loop object.
 +#
 +# Since: 7.1
 +##
 +{ 'struct': 'MainLoopProperties',
 +  'base': 'EventLoopBaseProperties',
 +  'data': {} }
 +
  ##
  # @MemoryBackendProperties:
  #
@@ -XXX,XX +XXX,XX @@
      { 'name': 'input-linux',
        'if': 'CONFIG_LINUX' },
      'iothread',
 +    'main-loop',
      { 'name': 'memory-backend-epc',
        'if': 'CONFIG_LINUX' },
      'memory-backend-file',
@@ -XXX,XX +XXX,XX @@
        'input-linux':                { 'type': 'InputLinuxProperties',
                                        'if': 'CONFIG_LINUX' },
        'iothread':                   'IothreadProperties',
 +      'main-loop':                  'MainLoopProperties',
        'memory-backend-epc':         { 'type': 'MemoryBackendEpcProperties',
                                        'if': 'CONFIG_LINUX' },
        'memory-backend-file':        'MemoryBackendFileProperties',
 diff --git a/meson.build b/meson.build
 index XXXXXXX..XXXXXXX 100644
 --- a/meson.build
 +++ b/meson.build
@@ -XXX,XX +XXX,XX @@ libqemuutil = static_library('qemuutil',
                               sources: util_ss.sources() + stub_ss.sources() + genh,
                               dependencies: [util_ss.dependencies(), libm, threads, glib, socket, malloc, pixman])
  qemuutil = declare_dependency(link_with: libqemuutil,
 -                              sources: genh + version_res)
 +                              sources: genh + version_res,
 +                              dependencies: [event_loop_base])
  if have_system or have_user
    decodetree = generator(find_program('scripts/decodetree.py'),
 diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h
 index XXXXXXX..XXXXXXX 100644
 --- a/include/qemu/main-loop.h
 +++ b/include/qemu/main-loop.h
@@ -XXX,XX +XXX,XX @@
  #define QEMU_MAIN_LOOP_H
  #include "block/aio.h"
 +#include "qom/object.h"
 +#include "sysemu/event-loop-base.h"
  #define SIG_IPI SIGUSR1
 +#define TYPE_MAIN_LOOP  "main-loop"
 +OBJECT_DECLARE_TYPE(MainLoop, MainLoopClass, MAIN_LOOP)
 +
 +struct MainLoop {
 +    EventLoopBase parent_obj;
 +};
 +typedef struct MainLoop MainLoop;
 +
  /**
   * qemu_init_main_loop: Set up the process so that it can run the main loop.
   *
 diff --git a/include/sysemu/event-loop-base.h b/include/sysemu/event-loop-base.h
 index XXXXXXX..XXXXXXX 100644
 --- a/include/sysemu/event-loop-base.h
 +++ b/include/sysemu/event-loop-base.h
@@ -XXX,XX +XXX,XX @@ struct EventLoopBaseClass {
      void (*init)(EventLoopBase *base, Error **errp);
      void (*update_params)(EventLoopBase *base, Error **errp);
 +    bool (*can_be_deleted)(EventLoopBase *base);
  };
  struct EventLoopBase {
 diff --git a/event-loop-base.c b/event-loop-base.c
 index XXXXXXX..XXXXXXX 100644
 --- a/event-loop-base.c
 +++ b/event-loop-base.c
@@ -XXX,XX +XXX,XX @@ static void event_loop_base_complete(UserCreatable *uc, Error **errp)
      }
  }
 +static bool event_loop_base_can_be_deleted(UserCreatable *uc)
 +{
 +    EventLoopBaseClass *bc = EVENT_LOOP_BASE_GET_CLASS(uc);
 +    EventLoopBase *backend = EVENT_LOOP_BASE(uc);
 +
 +    if (bc->can_be_deleted) {
 +        return bc->can_be_deleted(backend);
 +    }
 +
 +    return true;
 +}
 +
  static void event_loop_base_class_init(ObjectClass *klass, void *class_data)
  {
      UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
      ucc->complete = event_loop_base_complete;
 +    ucc->can_be_deleted = event_loop_base_can_be_deleted;
      object_class_property_add(klass, "aio-max-batch", "int",
                                event_loop_base_get_param,
 diff --git a/util/main-loop.c b/util/main-loop.c
 index XXXXXXX..XXXXXXX 100644
 --- a/util/main-loop.c
 +++ b/util/main-loop.c
@@ -XXX,XX +XXX,XX @@
  #include "qemu/error-report.h"
  #include "qemu/queue.h"
  #include "qemu/compiler.h"
 +#include "qom/object.h"
  #ifndef _WIN32
  #include <sys/wait.h>
@@ -XXX,XX +XXX,XX @@ int qemu_init_main_loop(Error **errp)
      return 0;
  }
 +static void main_loop_update_params(EventLoopBase *base, Error **errp)
 +{
 +    if (!qemu_aio_context) {
 +        error_setg(errp, "qemu aio context not ready");
 +        return;
 +    }
 +
 +    aio_context_set_aio_params(qemu_aio_context, base->aio_max_batch, errp);
 +}
 +
 +MainLoop *mloop;
 +
 +static void main_loop_init(EventLoopBase *base, Error **errp)
 +{
 +    MainLoop *m = MAIN_LOOP(base);
 +
 +    if (mloop) {
 +        error_setg(errp, "only one main-loop instance allowed");
 +        return;
 +    }
 +
 +    main_loop_update_params(base, errp);
 +
 +    mloop = m;
 +    return;
 +}
 +
 +static bool main_loop_can_be_deleted(EventLoopBase *base)
 +{
 +    return false;
 +}
 +
 +static void main_loop_class_init(ObjectClass *oc, void *class_data)
 +{
 +    EventLoopBaseClass *bc = EVENT_LOOP_BASE_CLASS(oc);
 +
 +    bc->init = main_loop_init;
 +    bc->update_params = main_loop_update_params;
 +    bc->can_be_deleted = main_loop_can_be_deleted;
 +}
 +
 +static const TypeInfo main_loop_info = {
 +    .name = TYPE_MAIN_LOOP,
 +    .parent = TYPE_EVENT_LOOP_BASE,
 +    .class_init = main_loop_class_init,
 +    .instance_size = sizeof(MainLoop),
 +};
 +
 +static void main_loop_register_types(void)
 +{
 +    type_register_static(&main_loop_info);
 +}
 +
 +type_init(main_loop_register_types)
 +
  static int max_priority;
  #ifndef _WIN32
 --
 .35.1

-[PULL for-7.0 1/2] block: Fix misleading hexadecimal format
+[PULL 3/3] util/event-loop-base: Introduce options to set the thread pool size
-From: Philippe Mathieu-Daudé <f4bug@amsat.org>
+From: Nicolas Saenz Julienne <nsaenzju@redhat.com>
-"0x%u" format is very misleading, replace by "0x%x".
+The thread pool regulates itself: when idle, it kills threads until
 empty, when in demand, it creates new threads until full. This behaviour
 doesn't play well with latency sensitive workloads where the price of
 creating a new thread is too high. For example, when paired with qemu's
 '-mlock', or using safety features like SafeStack, creating a new thread
 has been measured take multiple milliseconds.
-Found running:
+In order to mitigate this let's introduce a new 'EventLoopBase'
 property to set the thread pool size. The threads will be created during
 the pool's initialization or upon updating the property's value, remain
 available during its lifetime regardless of demand, and destroyed upon
 freeing it. A properly characterized workload will then be able to
 configure the pool to avoid any latency spikes.
-  $ git grep -E '0x%[0-9]*([lL]*|" ?PRI)[dDuU]' block/
+Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
+Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
-Inspired-by: Richard Henderson <richard.henderson@linaro.org>
+Acked-by: Markus Armbruster <armbru@redhat.com>
-Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
+Message-id: 20220425075723.20019-4-nsaenzju@redhat.com
 Reviewed-by: Hanna Reitz <hreitz@redhat.com>
 Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
 Reviewed-by: Denis V. Lunev <den@openvz.org>
 Message-id: 20220323114718.58714-2-philippe.mathieu.daude@gmail.com
 Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
 ---
- block/parallels-ext.c | 2 +-
+ qapi/qom.json                    | 10 +++++-
-file changed, 1 insertion(+), 1 deletion(-)
+ include/block/aio.h              | 10 ++++++
  include/block/thread-pool.h      |  3 ++
  include/sysemu/event-loop-base.h |  4 +++
  event-loop-base.c                | 23 +++++++++++++
  iothread.c                       |  3 ++
  util/aio-posix.c                 |  1 +
  util/async.c                     | 20 ++++++++++++
  util/main-loop.c                 |  9 ++++++
  util/thread-pool.c               | 55 +++++++++++++++++++++++++++++---
 files changed, 133 insertions(+), 5 deletions(-)
-diff --git a/block/parallels-ext.c b/block/parallels-ext.c
+diff --git a/qapi/qom.json b/qapi/qom.json
 index XXXXXXX..XXXXXXX 100644
---- a/block/parallels-ext.c
+--- a/qapi/qom.json
-+++ b/block/parallels-ext.c
++++ b/qapi/qom.json
-@@ -XXX,XX +XXX,XX @@ static int parallels_parse_format_extension(BlockDriverState *bs,
+@@ -XXX,XX +XXX,XX @@
  #                 0 means that the engine will use its default.
  #                 (default: 0)
  #
 +# @thread-pool-min: minimum number of threads reserved in the thread pool
 +#                   (default:0)
 +#
 +# @thread-pool-max: maximum number of threads the thread pool can contain
 +#                   (default:64)
 +#
  # Since: 7.1
  ##
  { 'struct': 'EventLoopBaseProperties',
 -  'data': { '*aio-max-batch': 'int' } }
 +  'data': { '*aio-max-batch': 'int',
 +            '*thread-pool-min': 'int',
 +            '*thread-pool-max': 'int' } }
  ##
  # @IothreadProperties:
 diff --git a/include/block/aio.h b/include/block/aio.h
 index XXXXXXX..XXXXXXX 100644
 --- a/include/block/aio.h
 +++ b/include/block/aio.h
@@ -XXX,XX +XXX,XX @@ struct AioContext {
      QSLIST_HEAD(, Coroutine) scheduled_coroutines;
      QEMUBH *co_schedule_bh;
 +    int thread_pool_min;
 +    int thread_pool_max;
      /* Thread pool for performing work and receiving completion callbacks.
       * Has its own locking.
       */
@@ -XXX,XX +XXX,XX @@ void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,
  void aio_context_set_aio_params(AioContext *ctx, int64_t max_batch,
                                  Error **errp);
 +/**
 + * aio_context_set_thread_pool_params:
 + * @ctx: the aio context
 + * @min: min number of threads to have readily available in the thread pool
 + * @min: max number of threads the thread pool can contain
 + */
 +void aio_context_set_thread_pool_params(AioContext *ctx, int64_t min,
 +                                        int64_t max, Error **errp);
  #endif
 diff --git a/include/block/thread-pool.h b/include/block/thread-pool.h
 index XXXXXXX..XXXXXXX 100644
 --- a/include/block/thread-pool.h
 +++ b/include/block/thread-pool.h
@@ -XXX,XX +XXX,XX @@
  #include "block/block.h"
 +#define THREAD_POOL_MAX_THREADS_DEFAULT         64
 +
  typedef int ThreadPoolFunc(void *opaque);
  typedef struct ThreadPool ThreadPool;
@@ -XXX,XX +XXX,XX @@ BlockAIOCB *thread_pool_submit_aio(ThreadPool *pool,
  int coroutine_fn thread_pool_submit_co(ThreadPool *pool,
          ThreadPoolFunc *func, void *arg);
  void thread_pool_submit(ThreadPool *pool, ThreadPoolFunc *func, void *arg);
 +void thread_pool_update_params(ThreadPool *pool, struct AioContext *ctx);
  #endif
 diff --git a/include/sysemu/event-loop-base.h b/include/sysemu/event-loop-base.h
 index XXXXXXX..XXXXXXX 100644
 --- a/include/sysemu/event-loop-base.h
 +++ b/include/sysemu/event-loop-base.h
@@ -XXX,XX +XXX,XX @@ struct EventLoopBase {
      /* AioContext AIO engine parameters */
      int64_t aio_max_batch;
 +
 +    /* AioContext thread pool parameters */
 +    int64_t thread_pool_min;
 +    int64_t thread_pool_max;
  };
  #endif
 diff --git a/event-loop-base.c b/event-loop-base.c
 index XXXXXXX..XXXXXXX 100644
 --- a/event-loop-base.c
 +++ b/event-loop-base.c
@@ -XXX,XX +XXX,XX @@
  #include "qemu/osdep.h"
  #include "qom/object_interfaces.h"
  #include "qapi/error.h"
 +#include "block/thread-pool.h"
  #include "sysemu/event-loop-base.h"
  typedef struct {
@@ -XXX,XX +XXX,XX @@ typedef struct {
      ptrdiff_t offset; /* field's byte offset in EventLoopBase struct */
  } EventLoopBaseParamInfo;
 +static void event_loop_base_instance_init(Object *obj)
 +{
 +    EventLoopBase *base = EVENT_LOOP_BASE(obj);
 +
 +    base->thread_pool_max = THREAD_POOL_MAX_THREADS_DEFAULT;
 +}
 +
  static EventLoopBaseParamInfo aio_max_batch_info = {
      "aio-max-batch", offsetof(EventLoopBase, aio_max_batch),
  };
 +static EventLoopBaseParamInfo thread_pool_min_info = {
 +    "thread-pool-min", offsetof(EventLoopBase, thread_pool_min),
 +};
 +static EventLoopBaseParamInfo thread_pool_max_info = {
 +    "thread-pool-max", offsetof(EventLoopBase, thread_pool_max),
 +};
  static void event_loop_base_get_param(Object *obj, Visitor *v,
          const char *name, void *opaque, Error **errp)
@@ -XXX,XX +XXX,XX @@ static void event_loop_base_class_init(ObjectClass *klass, void *class_data)
                                event_loop_base_get_param,
                                event_loop_base_set_param,
                                NULL, &aio_max_batch_info);
 +    object_class_property_add(klass, "thread-pool-min", "int",
 +                              event_loop_base_get_param,
 +                              event_loop_base_set_param,
 +                              NULL, &thread_pool_min_info);
 +    object_class_property_add(klass, "thread-pool-max", "int",
 +                              event_loop_base_get_param,
 +                              event_loop_base_set_param,
 +                              NULL, &thread_pool_max_info);
  }
  static const TypeInfo event_loop_base_info = {
      .name = TYPE_EVENT_LOOP_BASE,
      .parent = TYPE_OBJECT,
      .instance_size = sizeof(EventLoopBase),
 +    .instance_init = event_loop_base_instance_init,
      .class_size = sizeof(EventLoopBaseClass),
      .class_init = event_loop_base_class_init,
      .abstract = true,
 diff --git a/iothread.c b/iothread.c
 index XXXXXXX..XXXXXXX 100644
 --- a/iothread.c
 +++ b/iothread.c
@@ -XXX,XX +XXX,XX @@ static void iothread_set_aio_context_params(EventLoopBase *base, Error **errp)
      aio_context_set_aio_params(iothread->ctx,
                                 iothread->parent_obj.aio_max_batch,
                                 errp);
 +
 +    aio_context_set_thread_pool_params(iothread->ctx, base->thread_pool_min,
 +                                       base->thread_pool_max, errp);
  }
 diff --git a/util/aio-posix.c b/util/aio-posix.c
 index XXXXXXX..XXXXXXX 100644
 --- a/util/aio-posix.c
 +++ b/util/aio-posix.c
@@ -XXX,XX +XXX,XX @@
  #include "qemu/osdep.h"
  #include "block/block.h"
 +#include "block/thread-pool.h"
  #include "qemu/main-loop.h"
  #include "qemu/rcu.h"
  #include "qemu/rcu_queue.h"
 diff --git a/util/async.c b/util/async.c
 index XXXXXXX..XXXXXXX 100644
 --- a/util/async.c
 +++ b/util/async.c
@@ -XXX,XX +XXX,XX @@ AioContext *aio_context_new(Error **errp)
      ctx->aio_max_batch = 0;
 +    ctx->thread_pool_min = 0;
 +    ctx->thread_pool_max = THREAD_POOL_MAX_THREADS_DEFAULT;
 +
      return ctx;
  fail:
      g_source_destroy(&ctx->source);
@@ -XXX,XX +XXX,XX @@ void qemu_set_current_aio_context(AioContext *ctx)
      assert(!get_my_aiocontext());
      set_my_aiocontext(ctx);
  }
 +
 +void aio_context_set_thread_pool_params(AioContext *ctx, int64_t min,
 +                                        int64_t max, Error **errp)
 +{
 +
 +    if (min > max || !max || min > INT_MAX || max > INT_MAX) {
 +        error_setg(errp, "bad thread-pool-min/thread-pool-max values");
 +        return;
 +    }
 +
 +    ctx->thread_pool_min = min;
 +    ctx->thread_pool_max = max;
 +
 +    if (ctx->thread_pool) {
 +        thread_pool_update_params(ctx->thread_pool, ctx);
 +    }
 +}
 diff --git a/util/main-loop.c b/util/main-loop.c
 index XXXXXXX..XXXXXXX 100644
 --- a/util/main-loop.c
 +++ b/util/main-loop.c
@@ -XXX,XX +XXX,XX @@
  #include "sysemu/replay.h"
  #include "qemu/main-loop.h"
  #include "block/aio.h"
 +#include "block/thread-pool.h"
  #include "qemu/error-report.h"
  #include "qemu/queue.h"
  #include "qemu/compiler.h"
@@ -XXX,XX +XXX,XX @@ int qemu_init_main_loop(Error **errp)
  static void main_loop_update_params(EventLoopBase *base, Error **errp)
  {
 +    ERRP_GUARD();
 +
      if (!qemu_aio_context) {
          error_setg(errp, "qemu aio context not ready");
          return;
      }
      aio_context_set_aio_params(qemu_aio_context, base->aio_max_batch, errp);
 +    if (*errp) {
 +        return;
 +    }
 +
 +    aio_context_set_thread_pool_params(qemu_aio_context, base->thread_pool_min,
 +                                       base->thread_pool_max, errp);
  }
  MainLoop *mloop;
 diff --git a/util/thread-pool.c b/util/thread-pool.c
 index XXXXXXX..XXXXXXX 100644
 --- a/util/thread-pool.c
 +++ b/util/thread-pool.c
@@ -XXX,XX +XXX,XX @@ struct ThreadPool {
      QemuMutex lock;
      QemuCond worker_stopped;
      QemuSemaphore sem;
 -    int max_threads;
      QEMUBH *new_thread_bh;
      /* The following variables are only accessed from one AioContext. */
@@ -XXX,XX +XXX,XX @@ struct ThreadPool {
      int new_threads;     /* backlog of threads we need to create */
      int pending_threads; /* threads created but not running yet */
      bool stopping;
 +    int min_threads;
 +    int max_threads;
  };
 +static inline bool back_to_sleep(ThreadPool *pool, int ret)
 +{
 +    /*
 +     * The semaphore timed out, we should exit the loop except when:
 +     *  - There is work to do, we raced with the signal.
 +     *  - The max threads threshold just changed, we raced with the signal.
 +     *  - The thread pool forces a minimum number of readily available threads.
 +     */
 +    if (ret == -1 && (!QTAILQ_EMPTY(&pool->request_list) ||
 +            pool->cur_threads > pool->max_threads ||
 +            pool->cur_threads <= pool->min_threads)) {
 +            return true;
 +    }
 +
 +    return false;
 +}
 +
  static void *worker_thread(void *opaque)
  {
      ThreadPool *pool = opaque;
@@ -XXX,XX +XXX,XX @@ static void *worker_thread(void *opaque)
              ret = qemu_sem_timedwait(&pool->sem, 10000);
              qemu_mutex_lock(&pool->lock);
              pool->idle_threads--;
 -        } while (ret == -1 && !QTAILQ_EMPTY(&pool->request_list));
 -        if (ret == -1 || pool->stopping) {
 +        } while (back_to_sleep(pool, ret));
 +        if (ret == -1 || pool->stopping ||
 +            pool->cur_threads > pool->max_threads) {
              break;
-         default:
--            error_setg(errp, "Unknown feature: 0x%" PRIu64, fh.magic);
-+            error_setg(errp, "Unknown feature: 0x%" PRIx64, fh.magic);
-             goto fail;
          }
+@@ -XXX,XX +XXX,XX @@ void thread_pool_submit(ThreadPool *pool, ThreadPoolFunc *func, void *arg)
+     thread_pool_submit_aio(pool, func, arg, NULL, NULL);
+ }
++void thread_pool_update_params(ThreadPool *pool, AioContext *ctx)
++{
++    qemu_mutex_lock(&pool->lock);
++
++    pool->min_threads = ctx->thread_pool_min;
++    pool->max_threads = ctx->thread_pool_max;
++
++    /*
++     * We either have to:
++     *  - Increase the number available of threads until over the min_threads
++     *    threshold.
++     *  - Decrease the number of available threads until under the max_threads
++     *    threshold.
++     *  - Do nothing. The current number of threads fall in between the min and
++     *    max thresholds. We'll let the pool manage itself.
++     */
++    for (int i = pool->cur_threads; i < pool->min_threads; i++) {
++        spawn_thread(pool);
++    }
++
++    for (int i = pool->cur_threads; i > pool->max_threads; i--) {
++        qemu_sem_post(&pool->sem);
++    }
++
++    qemu_mutex_unlock(&pool->lock);
++}
++
+ static void thread_pool_init_one(ThreadPool *pool, AioContext *ctx)
+ {
+     if (!ctx) {
+@@ -XXX,XX +XXX,XX @@ static void thread_pool_init_one(ThreadPool *pool, AioContext *ctx)
+     qemu_mutex_init(&pool->lock);
+     qemu_cond_init(&pool->worker_stopped);
+     qemu_sem_init(&pool->sem, 0);
+-    pool->max_threads = 64;
+     pool->new_thread_bh = aio_bh_new(ctx, spawn_thread_bh_fn, pool);
+     QLIST_INIT(&pool->head);
+     QTAILQ_INIT(&pool->request_list);
++
++    thread_pool_update_params(pool, ctx);
+ }
+ ThreadPool *thread_pool_new(AioContext *ctx)
 --
 .35.1

The following changes since commit 15ef89d2a1a7b93845a6b09c2ee8e1979f6eb30b:

Update version for v7.0.0-rc1 release (2022-03-22 22:58:44 +0000)

are available in the Git repository at:

https://gitlab.com/stefanha/qemu.git tags/block-pull-request

for you to fetch changes up to 2539eade4f689eda7e9fe45486f18334bfbafaf0:

hw: Fix misleading hexadecimal format (2022-03-24 10:38:42 +0000)

----------------------------------------------------------------
Pull request

Philippe found cases where the 0x%d format string was used, leading to
misleading output. The patches look harmless and could save people time, so I
think it's worth including them in 7.0.

----------------------------------------------------------------

Philippe Mathieu-Daudé (2):
  block: Fix misleading hexadecimal format
  hw: Fix misleading hexadecimal format

-- 
2.35.1

From: Philippe Mathieu-Daudé <f4bug@amsat.org>

"0x%u" format is very misleading, replace by "0x%x".

Found running:

$ git grep -E '0x%[0-9]*([lL]*|" ?PRI)[dDuU]' block/

Inspired-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
Message-id: 20220323114718.58714-2-philippe.mathieu.daude@gmail.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/parallels-ext.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/parallels-ext.c b/block/parallels-ext.c
index XXXXXXX..XXXXXXX 100644
--- a/block/parallels-ext.c
+++ b/block/parallels-ext.c
@@ -XXX,XX +XXX,XX @@ static int parallels_parse_format_extension(BlockDriverState *bs,
             break;
 
         default:
-            error_setg(errp, "Unknown feature: 0x%" PRIu64, fh.magic);
+            error_setg(errp, "Unknown feature: 0x%" PRIx64, fh.magic);
             goto fail;
         }
 
-- 
2.35.1

From: Philippe Mathieu-Daudé <f4bug@amsat.org>

"0x%u" format is very misleading, replace by "0x%x".

Found running:

$ git grep -E '0x%[0-9]*([lL]*|" ?PRI)[dDuU]' hw/

Inspired-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20220323114718.58714-3-philippe.mathieu.daude@gmail.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/i386/sgx.c        | 2 +-
 hw/i386/trace-events | 6 +++---
 hw/misc/trace-events | 4 ++--
 hw/scsi/trace-events | 4 ++--
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/hw/i386/sgx.c b/hw/i386/sgx.c
index XXXXXXX..XXXXXXX 100644
--- a/hw/i386/sgx.c
+++ b/hw/i386/sgx.c
@@ -XXX,XX +XXX,XX @@ void pc_machine_init_sgx_epc(PCMachineState *pcms)
     }
 
     if ((sgx_epc->base + sgx_epc->size) < sgx_epc->base) {
-        error_report("Size of all 'sgx-epc' =0x%"PRIu64" causes EPC to wrap",
+        error_report("Size of all 'sgx-epc' =0x%"PRIx64" causes EPC to wrap",
                      sgx_epc->size);
         exit(EXIT_FAILURE);
     }
diff --git a/hw/i386/trace-events b/hw/i386/trace-events
index XXXXXXX..XXXXXXX 100644
--- a/hw/i386/trace-events
+++ b/hw/i386/trace-events
@@ -XXX,XX +XXX,XX @@ vtd_fault_disabled(void) "Fault processing disabled for context entry"
 vtd_replay_ce_valid(const char *mode, uint8_t bus, uint8_t dev, uint8_t fn, uint16_t domain, uint64_t hi, uint64_t lo) "%s: replay valid context device %02"PRIx8":%02"PRIx8".%02"PRIx8" domain 0x%"PRIx16" hi 0x%"PRIx64" lo 0x%"PRIx64
 vtd_replay_ce_invalid(uint8_t bus, uint8_t dev, uint8_t fn) "replay invalid context device %02"PRIx8":%02"PRIx8".%02"PRIx8
 vtd_page_walk_level(uint64_t addr, uint32_t level, uint64_t start, uint64_t end) "walk (base=0x%"PRIx64", level=%"PRIu32") iova range 0x%"PRIx64" - 0x%"PRIx64
-vtd_page_walk_one(uint16_t domain, uint64_t iova, uint64_t gpa, uint64_t mask, int perm) "domain 0x%"PRIu16" iova 0x%"PRIx64" -> gpa 0x%"PRIx64" mask 0x%"PRIx64" perm %d"
+vtd_page_walk_one(uint16_t domain, uint64_t iova, uint64_t gpa, uint64_t mask, int perm) "domain 0x%"PRIx16" iova 0x%"PRIx64" -> gpa 0x%"PRIx64" mask 0x%"PRIx64" perm %d"
 vtd_page_walk_one_skip_map(uint64_t iova, uint64_t mask, uint64_t translated) "iova 0x%"PRIx64" mask 0x%"PRIx64" translated 0x%"PRIx64
 vtd_page_walk_one_skip_unmap(uint64_t iova, uint64_t mask) "iova 0x%"PRIx64" mask 0x%"PRIx64
 vtd_page_walk_skip_read(uint64_t iova, uint64_t next) "Page walk skip iova 0x%"PRIx64" - 0x%"PRIx64" due to unable to read"
 vtd_page_walk_skip_reserve(uint64_t iova, uint64_t next) "Page walk skip iova 0x%"PRIx64" - 0x%"PRIx64" due to rsrv set"
 vtd_switch_address_space(uint8_t bus, uint8_t slot, uint8_t fn, bool on) "Device %02x:%02x.%x switching address space (iommu enabled=%d)"
 vtd_as_unmap_whole(uint8_t bus, uint8_t slot, uint8_t fn, uint64_t iova, uint64_t size) "Device %02x:%02x.%x start 0x%"PRIx64" size 0x%"PRIx64
-vtd_translate_pt(uint16_t sid, uint64_t addr) "source id 0x%"PRIu16", iova 0x%"PRIx64
-vtd_pt_enable_fast_path(uint16_t sid, bool success) "sid 0x%"PRIu16" %d"
+vtd_translate_pt(uint16_t sid, uint64_t addr) "source id 0x%"PRIx16", iova 0x%"PRIx64
+vtd_pt_enable_fast_path(uint16_t sid, bool success) "sid 0x%"PRIx16" %d"
 vtd_irq_generate(uint64_t addr, uint64_t data) "addr 0x%"PRIx64" data 0x%"PRIx64
 vtd_reg_read(uint64_t addr, uint64_t size) "addr 0x%"PRIx64" size 0x%"PRIx64
 vtd_reg_write(uint64_t addr, uint64_t size, uint64_t val) "addr 0x%"PRIx64" size 0x%"PRIx64" value 0x%"PRIx64
diff --git a/hw/misc/trace-events b/hw/misc/trace-events
index XXXXXXX..XXXXXXX 100644
--- a/hw/misc/trace-events
+++ b/hw/misc/trace-events
@@ -XXX,XX +XXX,XX @@
 # See docs/devel/tracing.rst for syntax documentation.
 
 # allwinner-cpucfg.c
-allwinner_cpucfg_cpu_reset(uint8_t cpu_id, uint32_t reset_addr) "id %u, reset_addr 0x%" PRIu32
+allwinner_cpucfg_cpu_reset(uint8_t cpu_id, uint32_t reset_addr) "id %u, reset_addr 0x%" PRIx32
 allwinner_cpucfg_read(uint64_t offset, uint64_t data, unsigned size) "offset 0x%" PRIx64 " data 0x%" PRIx64 " size %" PRIu32
 allwinner_cpucfg_write(uint64_t offset, uint64_t data, unsigned size) "offset 0x%" PRIx64 " data 0x%" PRIx64 " size %" PRIu32
 
@@ -XXX,XX +XXX,XX @@ imx7_gpr_write(uint64_t offset, uint64_t value) "addr 0x%08" PRIx64 "value 0x%08
 
 # mos6522.c
 mos6522_set_counter(int index, unsigned int val) "T%d.counter=%d"
-mos6522_get_next_irq_time(uint16_t latch, int64_t d, int64_t delta) "latch=%d counter=0x%"PRId64 " delta_next=0x%"PRId64
+mos6522_get_next_irq_time(uint16_t latch, int64_t d, int64_t delta) "latch=%d counter=0x%"PRIx64 " delta_next=0x%"PRIx64
 mos6522_set_sr_int(void) "set sr_int"
 mos6522_write(uint64_t addr, const char *name, uint64_t val) "reg=0x%"PRIx64 " [%s] val=0x%"PRIx64
 mos6522_read(uint64_t addr, const char *name, unsigned val) "reg=0x%"PRIx64 " [%s] val=0x%x"
diff --git a/hw/scsi/trace-events b/hw/scsi/trace-events
index XXXXXXX..XXXXXXX 100644
--- a/hw/scsi/trace-events
+++ b/hw/scsi/trace-events
@@ -XXX,XX +XXX,XX @@ lsi_bad_phase_interrupt(void) "Phase mismatch interrupt"
 lsi_bad_selection(uint32_t id) "Selected absent target %"PRIu32
 lsi_do_dma_unavailable(void) "DMA no data available"
 lsi_do_dma(uint64_t addr, int len) "DMA addr=0x%"PRIx64" len=%d"
-lsi_queue_command(uint32_t tag) "Queueing tag=0x%"PRId32
+lsi_queue_command(uint32_t tag) "Queueing tag=0x%"PRIx32
 lsi_add_msg_byte_error(void) "MSG IN data too long"
 lsi_add_msg_byte(uint8_t data) "MSG IN 0x%02x"
 lsi_reselect(int id) "Reselected target %d"
@@ -XXX,XX +XXX,XX @@ lsi_do_msgout_noop(void) "MSG: No Operation"
 lsi_do_msgout_extended(uint8_t msg, uint8_t len) "Extended message 0x%x (len %d)"
 lsi_do_msgout_ignored(const char *msg) "%s (ignored)"
 lsi_do_msgout_simplequeue(uint8_t select_tag) "SIMPLE queue tag=0x%x"
-lsi_do_msgout_abort(uint32_t tag) "MSG: ABORT TAG tag=0x%"PRId32
+lsi_do_msgout_abort(uint32_t tag) "MSG: ABORT TAG tag=0x%"PRIx32
 lsi_do_msgout_clearqueue(uint32_t tag) "MSG: CLEAR QUEUE tag=0x%"PRIx32
 lsi_do_msgout_busdevicereset(uint32_t tag) "MSG: BUS DEVICE RESET tag=0x%"PRIx32
 lsi_do_msgout_select(int id) "Select LUN %d"
-- 
2.35.1

The following changes since commit 9cf289af47bcfae5c75de37d8e5d6fd23705322c:

Merge tag 'qga-pull-request' of gitlab.com:marcandre.lureau/qemu into staging (2022-05-04 03:42:49 -0700)

are available in the Git repository at:

https://gitlab.com/stefanha/qemu.git tags/block-pull-request

for you to fetch changes up to bef2e050d6a7feb865854c65570c496ac5a8cf53:

util/event-loop-base: Introduce options to set the thread pool size (2022-05-04 17:02:19 +0100)

----------------------------------------------------------------
Pull request

Add new thread-pool-min/thread-pool-max parameters to control the thread pool
used for async I/O.

----------------------------------------------------------------

Nicolas Saenz Julienne (3):
  Introduce event-loop-base abstract class
  util/main-loop: Introduce the main loop into QOM
  util/event-loop-base: Introduce options to set the thread pool size

-- 
2.35.1

From: Nicolas Saenz Julienne <nsaenzju@redhat.com>

Introduce the 'event-loop-base' abstract class, it'll hold the
properties common to all event loops and provide the necessary hooks for
their creation and maintenance. Then have iothread inherit from it.

EventLoopBaseClass is defined as user creatable and provides a hook for
its children to attach themselves to the user creatable class 'complete'
function. It also provides an update_params() callback to propagate
property changes onto its children.

The new 'event-loop-base' class will live in the root directory. It is
built on its own using the 'link_whole' option (there are no direct
function dependencies between the class and its children, it all happens
trough 'constructor' magic). And also imposes new compilation
dependencies:

qom <- event-loop-base <- blockdev (iothread.c)

And in subsequent patches:

qom <- event-loop-base <- qemuutil (util/main-loop.c)

All this forced some amount of reordering in meson.build:

- Moved qom build definition before qemuutil. Doing it the other way
   around (i.e. moving qemuutil after qom) isn't possible as a lot of
   core libraries that live in between the two depend on it.

- Process the 'hw' subdir earlier, as it introduces files into the
   'qom' source set.

No functional changes intended.

Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-id: 20220425075723.20019-2-nsaenzju@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 qapi/qom.json                    |  22 +++++--
 meson.build                      |  23 ++++---
 include/sysemu/event-loop-base.h |  36 +++++++++++
 include/sysemu/iothread.h        |   6 +-
 event-loop-base.c                | 104 +++++++++++++++++++++++++++++++
 iothread.c                       |  65 ++++++-------------
 6 files changed, 192 insertions(+), 64 deletions(-)
 create mode 100644 include/sysemu/event-loop-base.h
 create mode 100644 event-loop-base.c

diff --git a/qapi/qom.json b/qapi/qom.json
index XXXXXXX..XXXXXXX 100644
--- a/qapi/qom.json
+++ b/qapi/qom.json
@@ -XXX,XX +XXX,XX @@
             '*repeat': 'bool',
             '*grab-toggle': 'GrabToggleKeys' } }
 
+##
+# @EventLoopBaseProperties:
+#
+# Common properties for event loops
+#
+# @aio-max-batch: maximum number of requests in a batch for the AIO engine,
+#                 0 means that the engine will use its default.
+#                 (default: 0)
+#
+# Since: 7.1
+##
+{ 'struct': 'EventLoopBaseProperties',
+  'data': { '*aio-max-batch': 'int' } }
+
 ##
 # @IothreadProperties:
 #
@@ -XXX,XX +XXX,XX @@
 #               algorithm detects it is spending too long polling without
 #               encountering events. 0 selects a default behaviour (default: 0)
 #
-# @aio-max-batch: maximum number of requests in a batch for the AIO engine,
-#                 0 means that the engine will use its default
-#                 (default:0, since 6.1)
+# The @aio-max-batch option is available since 6.1.
 #
 # Since: 2.0
 ##
 { 'struct': 'IothreadProperties',
+  'base': 'EventLoopBaseProperties',
   'data': { '*poll-max-ns': 'int',
             '*poll-grow': 'int',
-            '*poll-shrink': 'int',
-            '*aio-max-batch': 'int' } }
+            '*poll-shrink': 'int' } }
 
 ##
 # @MemoryBackendProperties:
diff --git a/meson.build b/meson.build
index XXXXXXX..XXXXXXX 100644
--- a/meson.build
+++ b/meson.build
@@ -XXX,XX +XXX,XX @@ subdir('qom')
 subdir('authz')
 subdir('crypto')
 subdir('ui')
+subdir('hw')
 
 
 if enable_modules
@@ -XXX,XX +XXX,XX @@ if enable_modules
   modulecommon = declare_dependency(link_whole: libmodulecommon, compile_args: '-DBUILD_DSO')
 endif
 
+qom_ss = qom_ss.apply(config_host, strict: false)
+libqom = static_library('qom', qom_ss.sources() + genh,
+                        dependencies: [qom_ss.dependencies()],
+                        name_suffix: 'fa')
+qom = declare_dependency(link_whole: libqom)
+
+event_loop_base = files('event-loop-base.c')
+event_loop_base = static_library('event-loop-base', sources: event_loop_base + genh,
+                                 build_by_default: true)
+event_loop_base = declare_dependency(link_whole: event_loop_base,
+                                     dependencies: [qom])
+
 stub_ss = stub_ss.apply(config_all, strict: false)
 
 util_ss.add_all(trace_ss)
@@ -XXX,XX +XXX,XX @@ subdir('monitor')
 subdir('net')
 subdir('replay')
 subdir('semihosting')
-subdir('hw')
 subdir('tcg')
 subdir('fpu')
 subdir('accel')
@@ -XXX,XX +XXX,XX @@ qemu_syms = custom_target('qemu.syms', output: 'qemu.syms',
                              capture: true,
                              command: [undefsym, nm, '@INPUT@'])
 
-qom_ss = qom_ss.apply(config_host, strict: false)
-libqom = static_library('qom', qom_ss.sources() + genh,
-                        dependencies: [qom_ss.dependencies()],
-                        name_suffix: 'fa')
-
-qom = declare_dependency(link_whole: libqom)
-
 authz_ss = authz_ss.apply(config_host, strict: false)
 libauthz = static_library('authz', authz_ss.sources() + genh,
                           dependencies: [authz_ss.dependencies()],
@@ -XXX,XX +XXX,XX @@ libblockdev = static_library('blockdev', blockdev_ss.sources() + genh,
                              build_by_default: false)
 
 blockdev = declare_dependency(link_whole: [libblockdev],
-                              dependencies: [block])
+                              dependencies: [block, event_loop_base])
 
 qmp_ss = qmp_ss.apply(config_host, strict: false)
 libqmp = static_library('qmp', qmp_ss.sources() + genh,
diff --git a/include/sysemu/event-loop-base.h b/include/sysemu/event-loop-base.h
new file mode 100644
index XXXXXXX..XXXXXXX
--- /dev/null
+++ b/include/sysemu/event-loop-base.h
@@ -XXX,XX +XXX,XX @@
+/*
+ * QEMU event-loop backend
+ *
+ * Copyright (C) 2022 Red Hat Inc
+ *
+ * Authors:
+ *  Nicolas Saenz Julienne <nsaenzju@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+#ifndef QEMU_EVENT_LOOP_BASE_H
+#define QEMU_EVENT_LOOP_BASE_H
+
+#include "qom/object.h"
+#include "block/aio.h"
+#include "qemu/typedefs.h"
+
+#define TYPE_EVENT_LOOP_BASE         "event-loop-base"
+OBJECT_DECLARE_TYPE(EventLoopBase, EventLoopBaseClass,
+                    EVENT_LOOP_BASE)
+
+struct EventLoopBaseClass {
+    ObjectClass parent_class;
+
+    void (*init)(EventLoopBase *base, Error **errp);
+    void (*update_params)(EventLoopBase *base, Error **errp);
+};
+
+struct EventLoopBase {
+    Object parent;
+
+    /* AioContext AIO engine parameters */
+    int64_t aio_max_batch;
+};
+#endif
diff --git a/include/sysemu/iothread.h b/include/sysemu/iothread.h
index XXXXXXX..XXXXXXX 100644
--- a/include/sysemu/iothread.h
+++ b/include/sysemu/iothread.h
@@ -XXX,XX +XXX,XX @@
 #include "block/aio.h"
 #include "qemu/thread.h"
 #include "qom/object.h"
+#include "sysemu/event-loop-base.h"
 
 #define TYPE_IOTHREAD "iothread"
 
 struct IOThread {
-    Object parent_obj;
+    EventLoopBase parent_obj;
 
     QemuThread thread;
     AioContext *ctx;
@@ -XXX,XX +XXX,XX @@ struct IOThread {
     int64_t poll_max_ns;
     int64_t poll_grow;
     int64_t poll_shrink;
-
-    /* AioContext AIO engine parameters */
-    int64_t aio_max_batch;
 };
 typedef struct IOThread IOThread;
 
diff --git a/event-loop-base.c b/event-loop-base.c
new file mode 100644
index XXXXXXX..XXXXXXX
--- /dev/null
+++ b/event-loop-base.c
@@ -XXX,XX +XXX,XX @@
+/*
+ * QEMU event-loop base
+ *
+ * Copyright (C) 2022 Red Hat Inc
+ *
+ * Authors:
+ *  Stefan Hajnoczi <stefanha@redhat.com>
+ *  Nicolas Saenz Julienne <nsaenzju@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qom/object_interfaces.h"
+#include "qapi/error.h"
+#include "sysemu/event-loop-base.h"
+
+typedef struct {
+    const char *name;
+    ptrdiff_t offset; /* field's byte offset in EventLoopBase struct */
+} EventLoopBaseParamInfo;
+
+static EventLoopBaseParamInfo aio_max_batch_info = {
+    "aio-max-batch", offsetof(EventLoopBase, aio_max_batch),
+};
+
+static void event_loop_base_get_param(Object *obj, Visitor *v,
+        const char *name, void *opaque, Error **errp)
+{
+    EventLoopBase *event_loop_base = EVENT_LOOP_BASE(obj);
+    EventLoopBaseParamInfo *info = opaque;
+    int64_t *field = (void *)event_loop_base + info->offset;
+
+    visit_type_int64(v, name, field, errp);
+}
+
+static void event_loop_base_set_param(Object *obj, Visitor *v,
+        const char *name, void *opaque, Error **errp)
+{
+    EventLoopBaseClass *bc = EVENT_LOOP_BASE_GET_CLASS(obj);
+    EventLoopBase *base = EVENT_LOOP_BASE(obj);
+    EventLoopBaseParamInfo *info = opaque;
+    int64_t *field = (void *)base + info->offset;
+    int64_t value;
+
+    if (!visit_type_int64(v, name, &value, errp)) {
+        return;
+    }
+
+    if (value < 0) {
+        error_setg(errp, "%s value must be in range [0, %" PRId64 "]",
+                   info->name, INT64_MAX);
+        return;
+    }
+
+    *field = value;
+
+    if (bc->update_params) {
+        bc->update_params(base, errp);
+    }
+
+    return;
+}
+
+static void event_loop_base_complete(UserCreatable *uc, Error **errp)
+{
+    EventLoopBaseClass *bc = EVENT_LOOP_BASE_GET_CLASS(uc);
+    EventLoopBase *base = EVENT_LOOP_BASE(uc);
+
+    if (bc->init) {
+        bc->init(base, errp);
+    }
+}
+
+static void event_loop_base_class_init(ObjectClass *klass, void *class_data)
+{
+    UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
+    ucc->complete = event_loop_base_complete;
+
+    object_class_property_add(klass, "aio-max-batch", "int",
+                              event_loop_base_get_param,
+                              event_loop_base_set_param,
+                              NULL, &aio_max_batch_info);
+}
+
+static const TypeInfo event_loop_base_info = {
+    .name = TYPE_EVENT_LOOP_BASE,
+    .parent = TYPE_OBJECT,
+    .instance_size = sizeof(EventLoopBase),
+    .class_size = sizeof(EventLoopBaseClass),
+    .class_init = event_loop_base_class_init,
+    .abstract = true,
+    .interfaces = (InterfaceInfo[]) {
+        { TYPE_USER_CREATABLE },
+        { }
+    }
+};
+
+static void register_types(void)
+{
+    type_register_static(&event_loop_base_info);
+}
+type_init(register_types);
diff --git a/iothread.c b/iothread.c
index XXXXXXX..XXXXXXX 100644
--- a/iothread.c
+++ b/iothread.c
@@ -XXX,XX +XXX,XX @@
 #include "qemu/module.h"
 #include "block/aio.h"
 #include "block/block.h"
+#include "sysemu/event-loop-base.h"
 #include "sysemu/iothread.h"
 #include "qapi/error.h"
 #include "qapi/qapi-commands-misc.h"
@@ -XXX,XX +XXX,XX @@ static void iothread_init_gcontext(IOThread *iothread)
     iothread->main_loop = g_main_loop_new(iothread->worker_context, TRUE);
 }
 
-static void iothread_set_aio_context_params(IOThread *iothread, Error **errp)
+static void iothread_set_aio_context_params(EventLoopBase *base, Error **errp)
 {
+    IOThread *iothread = IOTHREAD(base);
     ERRP_GUARD();
 
+    if (!iothread->ctx) {
+        return;
+    }
+
     aio_context_set_poll_params(iothread->ctx,
                                 iothread->poll_max_ns,
                                 iothread->poll_grow,
@@ -XXX,XX +XXX,XX @@ static void iothread_set_aio_context_params(IOThread *iothread, Error **errp)
     }
 
     aio_context_set_aio_params(iothread->ctx,
-                               iothread->aio_max_batch,
+                               iothread->parent_obj.aio_max_batch,
                                errp);
 }
 
-static void iothread_complete(UserCreatable *obj, Error **errp)
+
+static void iothread_init(EventLoopBase *base, Error **errp)
 {
     Error *local_error = NULL;
-    IOThread *iothread = IOTHREAD(obj);
+    IOThread *iothread = IOTHREAD(base);
     char *thread_name;
 
     iothread->stopping = false;
@@ -XXX,XX +XXX,XX @@ static void iothread_complete(UserCreatable *obj, Error **errp)
      */
     iothread_init_gcontext(iothread);
 
-    iothread_set_aio_context_params(iothread, &local_error);
+    iothread_set_aio_context_params(base, &local_error);
     if (local_error) {
         error_propagate(errp, local_error);
         aio_context_unref(iothread->ctx);
@@ -XXX,XX +XXX,XX @@ static void iothread_complete(UserCreatable *obj, Error **errp)
      * to inherit.
      */
     thread_name = g_strdup_printf("IO %s",
-                        object_get_canonical_path_component(OBJECT(obj)));
+                        object_get_canonical_path_component(OBJECT(base)));
     qemu_thread_create(&iothread->thread, thread_name, iothread_run,
                        iothread, QEMU_THREAD_JOINABLE);
     g_free(thread_name);
@@ -XXX,XX +XXX,XX @@ static IOThreadParamInfo poll_grow_info = {
 static IOThreadParamInfo poll_shrink_info = {
     "poll-shrink", offsetof(IOThread, poll_shrink),
 };
-static IOThreadParamInfo aio_max_batch_info = {
-    "aio-max-batch", offsetof(IOThread, aio_max_batch),
-};
 
 static void iothread_get_param(Object *obj, Visitor *v,
         const char *name, IOThreadParamInfo *info, Error **errp)
@@ -XXX,XX +XXX,XX @@ static void iothread_set_poll_param(Object *obj, Visitor *v,
     }
 }
 
-static void iothread_get_aio_param(Object *obj, Visitor *v,
-        const char *name, void *opaque, Error **errp)
-{
-    IOThreadParamInfo *info = opaque;
-
-    iothread_get_param(obj, v, name, info, errp);
-}
-
-static void iothread_set_aio_param(Object *obj, Visitor *v,
-        const char *name, void *opaque, Error **errp)
-{
-    IOThread *iothread = IOTHREAD(obj);
-    IOThreadParamInfo *info = opaque;
-
-    if (!iothread_set_param(obj, v, name, info, errp)) {
-        return;
-    }
-
-    if (iothread->ctx) {
-        aio_context_set_aio_params(iothread->ctx,
-                                   iothread->aio_max_batch,
-                                   errp);
-    }
-}
-
 static void iothread_class_init(ObjectClass *klass, void *class_data)
 {
-    UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
-    ucc->complete = iothread_complete;
+    EventLoopBaseClass *bc = EVENT_LOOP_BASE_CLASS(klass);
+
+    bc->init = iothread_init;
+    bc->update_params = iothread_set_aio_context_params;
 
     object_class_property_add(klass, "poll-max-ns", "int",
                               iothread_get_poll_param,
@@ -XXX,XX +XXX,XX @@ static void iothread_class_init(ObjectClass *klass, void *class_data)
                               iothread_get_poll_param,
                               iothread_set_poll_param,
                               NULL, &poll_shrink_info);
-    object_class_property_add(klass, "aio-max-batch", "int",
-                              iothread_get_aio_param,
-                              iothread_set_aio_param,
-                              NULL, &aio_max_batch_info);
 }
 
 static const TypeInfo iothread_info = {
     .name = TYPE_IOTHREAD,
-    .parent = TYPE_OBJECT,
+    .parent = TYPE_EVENT_LOOP_BASE,
     .class_init = iothread_class_init,
     .instance_size = sizeof(IOThread),
     .instance_init = iothread_instance_init,
     .instance_finalize = iothread_instance_finalize,
-    .interfaces = (InterfaceInfo[]) {
-        {TYPE_USER_CREATABLE},
-        {}
-    },
 };
 
 static void iothread_register_types(void)
@@ -XXX,XX +XXX,XX @@ static int query_one_iothread(Object *object, void *opaque)
     info->poll_max_ns = iothread->poll_max_ns;
     info->poll_grow = iothread->poll_grow;
     info->poll_shrink = iothread->poll_shrink;
-    info->aio_max_batch = iothread->aio_max_batch;
+    info->aio_max_batch = iothread->parent_obj.aio_max_batch;
 
     QAPI_LIST_APPEND(*tail, info);
     return 0;
-- 
2.35.1

From: Nicolas Saenz Julienne <nsaenzju@redhat.com>

'event-loop-base' provides basic property handling for all 'AioContext'
based event loops. So let's define a new 'MainLoopClass' that inherits
from it. This will permit tweaking the main loop's properties through
qapi as well as through the command line using the '-object' keyword[1].
Only one instance of 'MainLoopClass' might be created at any time.

'EventLoopBaseClass' learns a new callback, 'can_be_deleted()' so as to
mark 'MainLoop' as non-deletable.

[1] For example:
      -object main-loop,id=main-loop,aio-max-batch=<value>

Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-id: 20220425075723.20019-3-nsaenzju@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 qapi/qom.json                    | 13 ++++++++
 meson.build                      |  3 +-
 include/qemu/main-loop.h         | 10 ++++++
 include/sysemu/event-loop-base.h |  1 +
 event-loop-base.c                | 13 ++++++++
 util/main-loop.c                 | 56 ++++++++++++++++++++++++++++++++
 6 files changed, 95 insertions(+), 1 deletion(-)

diff --git a/qapi/qom.json b/qapi/qom.json
index XXXXXXX..XXXXXXX 100644
--- a/qapi/qom.json
+++ b/qapi/qom.json
@@ -XXX,XX +XXX,XX @@
             '*poll-grow': 'int',
             '*poll-shrink': 'int' } }
 
+##
+# @MainLoopProperties:
+#
+# Properties for the main-loop object.
+#
+# Since: 7.1
+##
+{ 'struct': 'MainLoopProperties',
+  'base': 'EventLoopBaseProperties',
+  'data': {} }
+
 ##
 # @MemoryBackendProperties:
 #
@@ -XXX,XX +XXX,XX @@
     { 'name': 'input-linux',
       'if': 'CONFIG_LINUX' },
     'iothread',
+    'main-loop',
     { 'name': 'memory-backend-epc',
       'if': 'CONFIG_LINUX' },
     'memory-backend-file',
@@ -XXX,XX +XXX,XX @@
       'input-linux':                { 'type': 'InputLinuxProperties',
                                       'if': 'CONFIG_LINUX' },
       'iothread':                   'IothreadProperties',
+      'main-loop':                  'MainLoopProperties',
       'memory-backend-epc':         { 'type': 'MemoryBackendEpcProperties',
                                       'if': 'CONFIG_LINUX' },
       'memory-backend-file':        'MemoryBackendFileProperties',
diff --git a/meson.build b/meson.build
index XXXXXXX..XXXXXXX 100644
--- a/meson.build
+++ b/meson.build
@@ -XXX,XX +XXX,XX @@ libqemuutil = static_library('qemuutil',
                              sources: util_ss.sources() + stub_ss.sources() + genh,
                              dependencies: [util_ss.dependencies(), libm, threads, glib, socket, malloc, pixman])
 qemuutil = declare_dependency(link_with: libqemuutil,
-                              sources: genh + version_res)
+                              sources: genh + version_res,
+                              dependencies: [event_loop_base])
 
 if have_system or have_user
   decodetree = generator(find_program('scripts/decodetree.py'),
diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h
index XXXXXXX..XXXXXXX 100644
--- a/include/qemu/main-loop.h
+++ b/include/qemu/main-loop.h
@@ -XXX,XX +XXX,XX @@
 #define QEMU_MAIN_LOOP_H
 
 #include "block/aio.h"
+#include "qom/object.h"
+#include "sysemu/event-loop-base.h"
 
 #define SIG_IPI SIGUSR1
 
+#define TYPE_MAIN_LOOP  "main-loop"
+OBJECT_DECLARE_TYPE(MainLoop, MainLoopClass, MAIN_LOOP)
+
+struct MainLoop {
+    EventLoopBase parent_obj;
+};
+typedef struct MainLoop MainLoop;
+
 /**
  * qemu_init_main_loop: Set up the process so that it can run the main loop.
  *
diff --git a/include/sysemu/event-loop-base.h b/include/sysemu/event-loop-base.h
index XXXXXXX..XXXXXXX 100644
--- a/include/sysemu/event-loop-base.h
+++ b/include/sysemu/event-loop-base.h
@@ -XXX,XX +XXX,XX @@ struct EventLoopBaseClass {
 
     void (*init)(EventLoopBase *base, Error **errp);
     void (*update_params)(EventLoopBase *base, Error **errp);
+    bool (*can_be_deleted)(EventLoopBase *base);
 };
 
 struct EventLoopBase {
diff --git a/event-loop-base.c b/event-loop-base.c
index XXXXXXX..XXXXXXX 100644
--- a/event-loop-base.c
+++ b/event-loop-base.c
@@ -XXX,XX +XXX,XX @@ static void event_loop_base_complete(UserCreatable *uc, Error **errp)
     }
 }
 
+static bool event_loop_base_can_be_deleted(UserCreatable *uc)
+{
+    EventLoopBaseClass *bc = EVENT_LOOP_BASE_GET_CLASS(uc);
+    EventLoopBase *backend = EVENT_LOOP_BASE(uc);
+
+    if (bc->can_be_deleted) {
+        return bc->can_be_deleted(backend);
+    }
+
+    return true;
+}
+
 static void event_loop_base_class_init(ObjectClass *klass, void *class_data)
 {
     UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
     ucc->complete = event_loop_base_complete;
+    ucc->can_be_deleted = event_loop_base_can_be_deleted;
 
     object_class_property_add(klass, "aio-max-batch", "int",
                               event_loop_base_get_param,
diff --git a/util/main-loop.c b/util/main-loop.c
index XXXXXXX..XXXXXXX 100644
--- a/util/main-loop.c
+++ b/util/main-loop.c
@@ -XXX,XX +XXX,XX @@
 #include "qemu/error-report.h"
 #include "qemu/queue.h"
 #include "qemu/compiler.h"
+#include "qom/object.h"
 
 #ifndef _WIN32
 #include <sys/wait.h>
@@ -XXX,XX +XXX,XX @@ int qemu_init_main_loop(Error **errp)
     return 0;
 }
 
+static void main_loop_update_params(EventLoopBase *base, Error **errp)
+{
+    if (!qemu_aio_context) {
+        error_setg(errp, "qemu aio context not ready");
+        return;
+    }
+
+    aio_context_set_aio_params(qemu_aio_context, base->aio_max_batch, errp);
+}
+
+MainLoop *mloop;
+
+static void main_loop_init(EventLoopBase *base, Error **errp)
+{
+    MainLoop *m = MAIN_LOOP(base);
+
+    if (mloop) {
+        error_setg(errp, "only one main-loop instance allowed");
+        return;
+    }
+
+    main_loop_update_params(base, errp);
+
+    mloop = m;
+    return;
+}
+
+static bool main_loop_can_be_deleted(EventLoopBase *base)
+{
+    return false;
+}
+
+static void main_loop_class_init(ObjectClass *oc, void *class_data)
+{
+    EventLoopBaseClass *bc = EVENT_LOOP_BASE_CLASS(oc);
+
+    bc->init = main_loop_init;
+    bc->update_params = main_loop_update_params;
+    bc->can_be_deleted = main_loop_can_be_deleted;
+}
+
+static const TypeInfo main_loop_info = {
+    .name = TYPE_MAIN_LOOP,
+    .parent = TYPE_EVENT_LOOP_BASE,
+    .class_init = main_loop_class_init,
+    .instance_size = sizeof(MainLoop),
+};
+
+static void main_loop_register_types(void)
+{
+    type_register_static(&main_loop_info);
+}
+
+type_init(main_loop_register_types)
+
 static int max_priority;
 
 #ifndef _WIN32
-- 
2.35.1

From: Nicolas Saenz Julienne <nsaenzju@redhat.com>

The thread pool regulates itself: when idle, it kills threads until
empty, when in demand, it creates new threads until full. This behaviour
doesn't play well with latency sensitive workloads where the price of
creating a new thread is too high. For example, when paired with qemu's
'-mlock', or using safety features like SafeStack, creating a new thread
has been measured take multiple milliseconds.

In order to mitigate this let's introduce a new 'EventLoopBase'
property to set the thread pool size. The threads will be created during
the pool's initialization or upon updating the property's value, remain
available during its lifetime regardless of demand, and destroyed upon
freeing it. A properly characterized workload will then be able to
configure the pool to avoid any latency spikes.

Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-id: 20220425075723.20019-4-nsaenzju@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 qapi/qom.json                    | 10 +++++-
 include/block/aio.h              | 10 ++++++
 include/block/thread-pool.h      |  3 ++
 include/sysemu/event-loop-base.h |  4 +++
 event-loop-base.c                | 23 +++++++++++++
 iothread.c                       |  3 ++
 util/aio-posix.c                 |  1 +
 util/async.c                     | 20 ++++++++++++
 util/main-loop.c                 |  9 ++++++
 util/thread-pool.c               | 55 +++++++++++++++++++++++++++++---
 10 files changed, 133 insertions(+), 5 deletions(-)

diff --git a/qapi/qom.json b/qapi/qom.json
index XXXXXXX..XXXXXXX 100644
--- a/qapi/qom.json
+++ b/qapi/qom.json
@@ -XXX,XX +XXX,XX @@
 #                 0 means that the engine will use its default.
 #                 (default: 0)
 #
+# @thread-pool-min: minimum number of threads reserved in the thread pool
+#                   (default:0)
+#
+# @thread-pool-max: maximum number of threads the thread pool can contain
+#                   (default:64)
+#
 # Since: 7.1
 ##
 { 'struct': 'EventLoopBaseProperties',
-  'data': { '*aio-max-batch': 'int' } }
+  'data': { '*aio-max-batch': 'int',
+            '*thread-pool-min': 'int',
+            '*thread-pool-max': 'int' } }
 
 ##
 # @IothreadProperties:
diff --git a/include/block/aio.h b/include/block/aio.h
index XXXXXXX..XXXXXXX 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -XXX,XX +XXX,XX @@ struct AioContext {
     QSLIST_HEAD(, Coroutine) scheduled_coroutines;
     QEMUBH *co_schedule_bh;
 
+    int thread_pool_min;
+    int thread_pool_max;
     /* Thread pool for performing work and receiving completion callbacks.
      * Has its own locking.
      */
@@ -XXX,XX +XXX,XX @@ void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,
 void aio_context_set_aio_params(AioContext *ctx, int64_t max_batch,
                                 Error **errp);
 
+/**
+ * aio_context_set_thread_pool_params:
+ * @ctx: the aio context
+ * @min: min number of threads to have readily available in the thread pool
+ * @min: max number of threads the thread pool can contain
+ */
+void aio_context_set_thread_pool_params(AioContext *ctx, int64_t min,
+                                        int64_t max, Error **errp);
 #endif
diff --git a/include/block/thread-pool.h b/include/block/thread-pool.h
index XXXXXXX..XXXXXXX 100644
--- a/include/block/thread-pool.h
+++ b/include/block/thread-pool.h
@@ -XXX,XX +XXX,XX @@
 
 #include "block/block.h"
 
+#define THREAD_POOL_MAX_THREADS_DEFAULT         64
+
 typedef int ThreadPoolFunc(void *opaque);
 
 typedef struct ThreadPool ThreadPool;
@@ -XXX,XX +XXX,XX @@ BlockAIOCB *thread_pool_submit_aio(ThreadPool *pool,
 int coroutine_fn thread_pool_submit_co(ThreadPool *pool,
         ThreadPoolFunc *func, void *arg);
 void thread_pool_submit(ThreadPool *pool, ThreadPoolFunc *func, void *arg);
+void thread_pool_update_params(ThreadPool *pool, struct AioContext *ctx);
 
 #endif
diff --git a/include/sysemu/event-loop-base.h b/include/sysemu/event-loop-base.h
index XXXXXXX..XXXXXXX 100644
--- a/include/sysemu/event-loop-base.h
+++ b/include/sysemu/event-loop-base.h
@@ -XXX,XX +XXX,XX @@ struct EventLoopBase {
 
     /* AioContext AIO engine parameters */
     int64_t aio_max_batch;
+
+    /* AioContext thread pool parameters */
+    int64_t thread_pool_min;
+    int64_t thread_pool_max;
 };
 #endif
diff --git a/event-loop-base.c b/event-loop-base.c
index XXXXXXX..XXXXXXX 100644
--- a/event-loop-base.c
+++ b/event-loop-base.c
@@ -XXX,XX +XXX,XX @@
 #include "qemu/osdep.h"
 #include "qom/object_interfaces.h"
 #include "qapi/error.h"
+#include "block/thread-pool.h"
 #include "sysemu/event-loop-base.h"
 
 typedef struct {
@@ -XXX,XX +XXX,XX @@ typedef struct {
     ptrdiff_t offset; /* field's byte offset in EventLoopBase struct */
 } EventLoopBaseParamInfo;
 
+static void event_loop_base_instance_init(Object *obj)
+{
+    EventLoopBase *base = EVENT_LOOP_BASE(obj);
+
+    base->thread_pool_max = THREAD_POOL_MAX_THREADS_DEFAULT;
+}
+
 static EventLoopBaseParamInfo aio_max_batch_info = {
     "aio-max-batch", offsetof(EventLoopBase, aio_max_batch),
 };
+static EventLoopBaseParamInfo thread_pool_min_info = {
+    "thread-pool-min", offsetof(EventLoopBase, thread_pool_min),
+};
+static EventLoopBaseParamInfo thread_pool_max_info = {
+    "thread-pool-max", offsetof(EventLoopBase, thread_pool_max),
+};
 
 static void event_loop_base_get_param(Object *obj, Visitor *v,
         const char *name, void *opaque, Error **errp)
@@ -XXX,XX +XXX,XX @@ static void event_loop_base_class_init(ObjectClass *klass, void *class_data)
                               event_loop_base_get_param,
                               event_loop_base_set_param,
                               NULL, &aio_max_batch_info);
+    object_class_property_add(klass, "thread-pool-min", "int",
+                              event_loop_base_get_param,
+                              event_loop_base_set_param,
+                              NULL, &thread_pool_min_info);
+    object_class_property_add(klass, "thread-pool-max", "int",
+                              event_loop_base_get_param,
+                              event_loop_base_set_param,
+                              NULL, &thread_pool_max_info);
 }
 
 static const TypeInfo event_loop_base_info = {
     .name = TYPE_EVENT_LOOP_BASE,
     .parent = TYPE_OBJECT,
     .instance_size = sizeof(EventLoopBase),
+    .instance_init = event_loop_base_instance_init,
     .class_size = sizeof(EventLoopBaseClass),
     .class_init = event_loop_base_class_init,
     .abstract = true,
diff --git a/iothread.c b/iothread.c
index XXXXXXX..XXXXXXX 100644
--- a/iothread.c
+++ b/iothread.c
@@ -XXX,XX +XXX,XX @@ static void iothread_set_aio_context_params(EventLoopBase *base, Error **errp)
     aio_context_set_aio_params(iothread->ctx,
                                iothread->parent_obj.aio_max_batch,
                                errp);
+
+    aio_context_set_thread_pool_params(iothread->ctx, base->thread_pool_min,
+                                       base->thread_pool_max, errp);
 }
 
 
diff --git a/util/aio-posix.c b/util/aio-posix.c
index XXXXXXX..XXXXXXX 100644
--- a/util/aio-posix.c
+++ b/util/aio-posix.c
@@ -XXX,XX +XXX,XX @@
 
 #include "qemu/osdep.h"
 #include "block/block.h"
+#include "block/thread-pool.h"
 #include "qemu/main-loop.h"
 #include "qemu/rcu.h"
 #include "qemu/rcu_queue.h"
diff --git a/util/async.c b/util/async.c
index XXXXXXX..XXXXXXX 100644
--- a/util/async.c
+++ b/util/async.c
@@ -XXX,XX +XXX,XX @@ AioContext *aio_context_new(Error **errp)
 
     ctx->aio_max_batch = 0;
 
+    ctx->thread_pool_min = 0;
+    ctx->thread_pool_max = THREAD_POOL_MAX_THREADS_DEFAULT;
+
     return ctx;
 fail:
     g_source_destroy(&ctx->source);
@@ -XXX,XX +XXX,XX @@ void qemu_set_current_aio_context(AioContext *ctx)
     assert(!get_my_aiocontext());
     set_my_aiocontext(ctx);
 }
+
+void aio_context_set_thread_pool_params(AioContext *ctx, int64_t min,
+                                        int64_t max, Error **errp)
+{
+
+    if (min > max || !max || min > INT_MAX || max > INT_MAX) {
+        error_setg(errp, "bad thread-pool-min/thread-pool-max values");
+        return;
+    }
+
+    ctx->thread_pool_min = min;
+    ctx->thread_pool_max = max;
+
+    if (ctx->thread_pool) {
+        thread_pool_update_params(ctx->thread_pool, ctx);
+    }
+}
diff --git a/util/main-loop.c b/util/main-loop.c
index XXXXXXX..XXXXXXX 100644
--- a/util/main-loop.c
+++ b/util/main-loop.c
@@ -XXX,XX +XXX,XX @@
 #include "sysemu/replay.h"
 #include "qemu/main-loop.h"
 #include "block/aio.h"
+#include "block/thread-pool.h"
 #include "qemu/error-report.h"
 #include "qemu/queue.h"
 #include "qemu/compiler.h"
@@ -XXX,XX +XXX,XX @@ int qemu_init_main_loop(Error **errp)
 
 static void main_loop_update_params(EventLoopBase *base, Error **errp)
 {
+    ERRP_GUARD();
+
     if (!qemu_aio_context) {
         error_setg(errp, "qemu aio context not ready");
         return;
     }
 
     aio_context_set_aio_params(qemu_aio_context, base->aio_max_batch, errp);
+    if (*errp) {
+        return;
+    }
+
+    aio_context_set_thread_pool_params(qemu_aio_context, base->thread_pool_min,
+                                       base->thread_pool_max, errp);
 }
 
 MainLoop *mloop;
diff --git a/util/thread-pool.c b/util/thread-pool.c
index XXXXXXX..XXXXXXX 100644
--- a/util/thread-pool.c
+++ b/util/thread-pool.c
@@ -XXX,XX +XXX,XX @@ struct ThreadPool {
     QemuMutex lock;
     QemuCond worker_stopped;
     QemuSemaphore sem;
-    int max_threads;
     QEMUBH *new_thread_bh;
 
     /* The following variables are only accessed from one AioContext. */
@@ -XXX,XX +XXX,XX @@ struct ThreadPool {
     int new_threads;     /* backlog of threads we need to create */
     int pending_threads; /* threads created but not running yet */
     bool stopping;
+    int min_threads;
+    int max_threads;
 };
 
+static inline bool back_to_sleep(ThreadPool *pool, int ret)
+{
+    /*
+     * The semaphore timed out, we should exit the loop except when:
+     *  - There is work to do, we raced with the signal.
+     *  - The max threads threshold just changed, we raced with the signal.
+     *  - The thread pool forces a minimum number of readily available threads.
+     */
+    if (ret == -1 && (!QTAILQ_EMPTY(&pool->request_list) ||
+            pool->cur_threads > pool->max_threads ||
+            pool->cur_threads <= pool->min_threads)) {
+            return true;
+    }
+
+    return false;
+}
+
 static void *worker_thread(void *opaque)
 {
     ThreadPool *pool = opaque;
@@ -XXX,XX +XXX,XX @@ static void *worker_thread(void *opaque)
             ret = qemu_sem_timedwait(&pool->sem, 10000);
             qemu_mutex_lock(&pool->lock);
             pool->idle_threads--;
-        } while (ret == -1 && !QTAILQ_EMPTY(&pool->request_list));
-        if (ret == -1 || pool->stopping) {
+        } while (back_to_sleep(pool, ret));
+        if (ret == -1 || pool->stopping ||
+            pool->cur_threads > pool->max_threads) {
             break;
         }
 
@@ -XXX,XX +XXX,XX @@ void thread_pool_submit(ThreadPool *pool, ThreadPoolFunc *func, void *arg)
     thread_pool_submit_aio(pool, func, arg, NULL, NULL);
 }
 
+void thread_pool_update_params(ThreadPool *pool, AioContext *ctx)
+{
+    qemu_mutex_lock(&pool->lock);
+
+    pool->min_threads = ctx->thread_pool_min;
+    pool->max_threads = ctx->thread_pool_max;
+
+    /*
+     * We either have to:
+     *  - Increase the number available of threads until over the min_threads
+     *    threshold.
+     *  - Decrease the number of available threads until under the max_threads
+     *    threshold.
+     *  - Do nothing. The current number of threads fall in between the min and
+     *    max thresholds. We'll let the pool manage itself.
+     */
+    for (int i = pool->cur_threads; i < pool->min_threads; i++) {
+        spawn_thread(pool);
+    }
+
+    for (int i = pool->cur_threads; i > pool->max_threads; i--) {
+        qemu_sem_post(&pool->sem);
+    }
+
+    qemu_mutex_unlock(&pool->lock);
+}
+
 static void thread_pool_init_one(ThreadPool *pool, AioContext *ctx)
 {
     if (!ctx) {
@@ -XXX,XX +XXX,XX @@ static void thread_pool_init_one(ThreadPool *pool, AioContext *ctx)
     qemu_mutex_init(&pool->lock);
     qemu_cond_init(&pool->worker_stopped);
     qemu_sem_init(&pool->sem, 0);
-    pool->max_threads = 64;
     pool->new_thread_bh = aio_bh_new(ctx, spawn_thread_bh_fn, pool);
 
     QLIST_INIT(&pool->head);
     QTAILQ_INIT(&pool->request_list);
+
+    thread_pool_update_params(pool, ctx);
 }
 
 ThreadPool *thread_pool_new(AioContext *ctx)
-- 
2.35.1