From: Magnus Kulke <magnuskulke@linux.microsoft.com>

Introduce the initial scaffold for the MSHV (Microsoft Hypervisor)
accelerator backend. This includes the basic directory structure and
stub implementations needed to integrate with QEMU's accelerator
framework.

Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
Link: https://lore.kernel.org/r/20250916164847.77883-8-magnuskulke@linux.microsoft.com
[Move include of linux/mshv.h in the per-target section; create
 include/system/mshv_int.h. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/system/mshv.h     |  12 ++++
 include/system/mshv_int.h |  41 +++++++++++
 accel/mshv/mshv-all.c     | 144 ++++++++++++++++++++++++++++++++++++++
 accel/meson.build         |   1 +
 accel/mshv/meson.build    |   6 ++
 5 files changed, 204 insertions(+)
 create mode 100644 include/system/mshv_int.h
 create mode 100644 accel/mshv/mshv-all.c
 create mode 100644 accel/mshv/meson.build

diff --git a/include/system/mshv.h b/include/system/mshv.h
index 2a504ed81f2..434ea9682e1 100644
--- a/include/system/mshv.h
+++ b/include/system/mshv.h
@@ -14,8 +14,17 @@
 #ifndef QEMU_MSHV_H
 #define QEMU_MSHV_H
 
+#include "qemu/osdep.h"
+#include "qemu/accel.h"
+#include "hw/hyperv/hyperv-proto.h"
+#include "hw/hyperv/hvhdk.h"
+#include "qapi/qapi-types-common.h"
+#include "system/memory.h"
+#include "accel/accel-ops.h"
+
 #ifdef COMPILING_PER_TARGET
 #ifdef CONFIG_MSHV
+#include <linux/mshv.h>
 #define CONFIG_MSHV_IS_POSSIBLE
 #endif
 #else
@@ -30,6 +39,9 @@ extern bool mshv_allowed;
 #endif
 #define mshv_msi_via_irqfd_enabled() false
 
+typedef struct MshvState MshvState;
+extern MshvState *mshv_state;
+
 /* interrupt */
 int mshv_irqchip_add_msi_route(int vector, PCIDevice *dev);
 int mshv_irqchip_update_msi_route(int virq, MSIMessage msg, PCIDevice *dev);
diff --git a/include/system/mshv_int.h b/include/system/mshv_int.h
new file mode 100644
index 00000000000..132491b599d
--- /dev/null
+++ b/include/system/mshv_int.h
@@ -0,0 +1,41 @@
+/*
+ * QEMU MSHV support
+ *
+ * Copyright Microsoft, Corp. 2025
+ *
+ * Authors: Ziqiao Zhou  <ziqiaozhou@microsoft.com>
+ *          Magnus Kulke <magnuskulke@microsoft.com>
+ *          Jinank Jain  <jinankjain@microsoft.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ */
+
+#ifndef QEMU_MSHV_INT_H
+#define QEMU_MSHV_INT_H
+
+struct AccelCPUState {
+    int cpufd;
+    bool dirty;
+};
+
+typedef struct MshvMemoryListener {
+    MemoryListener listener;
+    int as_id;
+} MshvMemoryListener;
+
+typedef struct MshvAddressSpace {
+    MshvMemoryListener *ml;
+    AddressSpace *as;
+} MshvAddressSpace;
+
+struct MshvState {
+    AccelState parent_obj;
+    int vm;
+    MshvMemoryListener memory_listener;
+    /* number of listeners */
+    int nr_as;
+    MshvAddressSpace *as;
+};
+
+#endif
diff --git a/accel/mshv/mshv-all.c b/accel/mshv/mshv-all.c
new file mode 100644
index 00000000000..ae12f0f58b9
--- /dev/null
+++ b/accel/mshv/mshv-all.c
@@ -0,0 +1,144 @@
+/*
+ * QEMU MSHV support
+ *
+ * Copyright Microsoft, Corp. 2025
+ *
+ * Authors:
+ *  Ziqiao Zhou       <ziqiaozhou@microsoft.com>
+ *  Magnus Kulke      <magnuskulke@microsoft.com>
+ *  Jinank Jain       <jinankjain@microsoft.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qemu/error-report.h"
+#include "qemu/event_notifier.h"
+#include "qemu/module.h"
+#include "qemu/main-loop.h"
+#include "hw/boards.h"
+
+#include "hw/hyperv/hvhdk.h"
+#include "hw/hyperv/hvhdk_mini.h"
+#include "hw/hyperv/hvgdk.h"
+#include "linux/mshv.h"
+
+#include "qemu/accel.h"
+#include "qemu/guest-random.h"
+#include "accel/accel-ops.h"
+#include "accel/accel-cpu-ops.h"
+#include "system/cpus.h"
+#include "system/runstate.h"
+#include "system/accel-blocker.h"
+#include "system/address-spaces.h"
+#include "system/mshv.h"
+#include "system/mshv_int.h"
+#include "system/reset.h"
+#include "trace.h"
+#include <err.h>
+#include <stdint.h>
+#include <sys/ioctl.h>
+
+#define TYPE_MSHV_ACCEL ACCEL_CLASS_NAME("mshv")
+
+DECLARE_INSTANCE_CHECKER(MshvState, MSHV_STATE, TYPE_MSHV_ACCEL)
+
+bool mshv_allowed;
+
+MshvState *mshv_state;
+
+static int mshv_init(AccelState *as, MachineState *ms)
+{
+    error_report("unimplemented");
+    abort();
+}
+
+static void mshv_start_vcpu_thread(CPUState *cpu)
+{
+    error_report("unimplemented");
+    abort();
+}
+
+static void mshv_cpu_synchronize_post_init(CPUState *cpu)
+{
+    error_report("unimplemented");
+    abort();
+}
+
+static void mshv_cpu_synchronize_post_reset(CPUState *cpu)
+{
+    error_report("unimplemented");
+    abort();
+}
+
+static void mshv_cpu_synchronize_pre_loadvm(CPUState *cpu)
+{
+    error_report("unimplemented");
+    abort();
+}
+
+static void mshv_cpu_synchronize(CPUState *cpu)
+{
+    error_report("unimplemented");
+    abort();
+}
+
+static bool mshv_cpus_are_resettable(void)
+{
+    error_report("unimplemented");
+    abort();
+}
+
+static void mshv_accel_class_init(ObjectClass *oc, const void *data)
+{
+    AccelClass *ac = ACCEL_CLASS(oc);
+
+    ac->name = "MSHV";
+    ac->init_machine = mshv_init;
+    ac->allowed = &mshv_allowed;
+}
+
+static void mshv_accel_instance_init(Object *obj)
+{
+    MshvState *s = MSHV_STATE(obj);
+
+    s->vm = 0;
+}
+
+static const TypeInfo mshv_accel_type = {
+    .name = TYPE_MSHV_ACCEL,
+    .parent = TYPE_ACCEL,
+    .instance_init = mshv_accel_instance_init,
+    .class_init = mshv_accel_class_init,
+    .instance_size = sizeof(MshvState),
+};
+
+static void mshv_accel_ops_class_init(ObjectClass *oc, const void *data)
+{
+    AccelOpsClass *ops = ACCEL_OPS_CLASS(oc);
+
+    ops->create_vcpu_thread = mshv_start_vcpu_thread;
+    ops->synchronize_post_init = mshv_cpu_synchronize_post_init;
+    ops->synchronize_post_reset = mshv_cpu_synchronize_post_reset;
+    ops->synchronize_state = mshv_cpu_synchronize;
+    ops->synchronize_pre_loadvm = mshv_cpu_synchronize_pre_loadvm;
+    ops->cpus_are_resettable = mshv_cpus_are_resettable;
+    ops->handle_interrupt = generic_handle_interrupt;
+}
+
+static const TypeInfo mshv_accel_ops_type = {
+    .name = ACCEL_OPS_NAME("mshv"),
+    .parent = TYPE_ACCEL_OPS,
+    .class_init = mshv_accel_ops_class_init,
+    .abstract = true,
+};
+
+static void mshv_type_init(void)
+{
+    type_register_static(&mshv_accel_type);
+    type_register_static(&mshv_accel_ops_type);
+}
+
+type_init(mshv_type_init);
diff --git a/accel/meson.build b/accel/meson.build
index 6349efe682f..983dfd0bd55 100644
--- a/accel/meson.build
+++ b/accel/meson.build
@@ -10,6 +10,7 @@ if have_system
   subdir('kvm')
   subdir('xen')
   subdir('stubs')
+  subdir('mshv')
 endif
 
 # qtest
diff --git a/accel/mshv/meson.build b/accel/mshv/meson.build
new file mode 100644
index 00000000000..4c03ac79219
--- /dev/null
+++ b/accel/mshv/meson.build
@@ -0,0 +1,6 @@
+mshv_ss = ss.source_set()
+mshv_ss.add(if_true: files(
+  'mshv-all.c'
+))
+
+specific_ss.add_all(when: 'CONFIG_MSHV', if_true: mshv_ss)
-- 
2.51.0