This patch maps /domain/cpu/cache element into -cpu parameters:

- <cache mode='passthrough'/> is translated to host-cache-info=on
- <cache level='3' mode='emulate'/> is transformed into l3-cache=on
- <cache mode='disable'/> is turned in host-cache-info=off,l3-cache=off

Any other <cache> element is forbidden.

The tricky part is detecting whether QEMU supports the CPU properties.

The 'host-cache-info' property is introduced in v2.4.0-1389-ge265e3e480,
earlier QEMU releases enabled host-cache-info by default and had no way
to disable it. If the property is present, it defaults to 'off' for any
QEMU until at least 2.9.0.

The 'l3-cache' property was introduced later by v2.7.0-200-g14c985cffa.
Earlier versions worked as if l3-cache=off was passed. For any QEMU
until at least 2.9.0 l3-cache is 'off' by default.

QEMU 2.9.0 was the first release which supports probing both properties
by running device-list-properties with typename=host-x86_64-cpu. Older
QEMU releases did not support device-list-properties command for CPU
devices. Thus we can't really rely on probing them and we can just use
query-cpu-model-expansion QMP command as a witness.

Because the cache property probing is only reliable for QEMU >= 2.9.0
when both are already supported for quite a few releases, we let QEMU
report an error if a specific cache mode is explicitly requested. The
other mode (or both if a user requested CPU cache to be disabled) is
explicitly turned off for QEMU >= 2.9.0 to avoid any surprises in case
the QEMU defaults change. Any older QEMU already turns them off so not
doing so explicitly does not make any harm.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
---
 src/qemu/qemu_capabilities.c                       |  8 ++++
 src/qemu/qemu_capabilities.h                       |  2 +
 src/qemu/qemu_command.c                            | 37 +++++++++++++++
 src/qemu/qemu_domain.c                             | 54 ++++++++++++++++++++++
 tests/qemucapabilitiesdata/caps_2.9.0.x86_64.xml   |  2 +
 .../qemuxml2argv-cpu-cache-disable.args            | 21 +++++++++
 .../qemuxml2argv-cpu-cache-disable.xml             | 20 ++++++++
 .../qemuxml2argv-cpu-cache-disable2.args           | 21 +++++++++
 .../qemuxml2argv-cpu-cache-disable2.xml            | 20 ++++++++
 .../qemuxml2argv-cpu-cache-disable3.args           | 22 +++++++++
 .../qemuxml2argv-cpu-cache-disable3.xml            | 20 ++++++++
 .../qemuxml2argv-cpu-cache-emulate-l2.xml          | 20 ++++++++
 .../qemuxml2argv-cpu-cache-emulate-l3.args         | 21 +++++++++
 .../qemuxml2argv-cpu-cache-emulate-l3.xml          | 20 ++++++++
 .../qemuxml2argv-cpu-cache-passthrough-l3.xml      | 20 ++++++++
 .../qemuxml2argv-cpu-cache-passthrough.args        | 21 +++++++++
 .../qemuxml2argv-cpu-cache-passthrough.xml         | 20 ++++++++
 .../qemuxml2argv-cpu-cache-passthrough2.args       | 21 +++++++++
 .../qemuxml2argv-cpu-cache-passthrough2.xml        | 20 ++++++++
 .../qemuxml2argv-cpu-cache-passthrough3.xml        | 20 ++++++++
 tests/qemuxml2argvtest.c                           | 16 +++++++
 21 files changed, 426 insertions(+)
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable.args
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable.xml
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable2.args
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable2.xml
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable3.args
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable3.xml
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-emulate-l2.xml
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-emulate-l3.args
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-emulate-l3.xml
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough-l3.xml
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough.args
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough.xml
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.args
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.xml
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough3.xml

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index cc3e1f808..5dd18f3c5 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -364,6 +364,8 @@ VIR_ENUM_IMPL(virQEMUCaps, QEMU_CAPS_LAST,
               "query-cpu-definitions", /* 250 */
               "block-write-threshold",
               "query-named-block-nodes",
+              "cpu-host-cache",
+              "cpu-l3-cache",
     );
 
 
@@ -4787,6 +4789,12 @@ virQEMUCapsInitQMPMonitor(virQEMUCapsPtr qemuCaps,
         virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_NVDIMM))
         virQEMUCapsClear(qemuCaps, QEMU_CAPS_DEVICE_NVDIMM);
 
+    if (ARCH_IS_X86(qemuCaps->arch) &&
+        virQEMUCapsGet(qemuCaps, QEMU_CAPS_QUERY_CPU_MODEL_EXPANSION)) {
+        virQEMUCapsSet(qemuCaps, QEMU_CAPS_CPU_HOST_CACHE);
+        virQEMUCapsSet(qemuCaps, QEMU_CAPS_CPU_L3_CACHE);
+    }
+
     ret = 0;
  cleanup:
     return ret;
diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
index a7eec52a9..b4f35012f 100644
--- a/src/qemu/qemu_capabilities.h
+++ b/src/qemu/qemu_capabilities.h
@@ -401,6 +401,8 @@ typedef enum {
     QEMU_CAPS_QUERY_CPU_DEFINITIONS, /* qmp query-cpu-definitions */
     QEMU_CAPS_BLOCK_WRITE_THRESHOLD, /* BLOCK_WRITE_THRESHOLD event */
     QEMU_CAPS_QUERY_NAMED_BLOCK_NODES, /* qmp query-named-block-nodes */
+    QEMU_CAPS_CPU_HOST_CACHE, /* host cpu supports host-cache-info property */
+    QEMU_CAPS_CPU_L3_CACHE, /* -cpu supports l3-cache property */
 
     QEMU_CAPS_LAST /* this must always be the last item */
 } virQEMUCapsFlags;
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 1116d2cd5..eb7404ead 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -7063,6 +7063,43 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
         have_cpu = true;
     }
 
+    if (def->cpu && def->cpu->cache) {
+        virCPUCacheDefPtr cache = def->cpu->cache;
+        bool hostOff = false;
+        bool l3Off = false;
+
+        if (!have_cpu)
+            virBufferAdd(&buf, default_model, -1);
+
+        switch (cache->mode) {
+        case VIR_CPU_CACHE_MODE_EMULATE:
+            virBufferAddLit(&buf, ",l3-cache=on");
+            hostOff = true;
+            break;
+
+        case VIR_CPU_CACHE_MODE_PASSTHROUGH:
+            virBufferAddLit(&buf, ",host-cache-info=on");
+            l3Off = true;
+            break;
+
+        case VIR_CPU_CACHE_MODE_DISABLE:
+            hostOff = l3Off = true;
+            break;
+
+        case VIR_CPU_CACHE_MODE_LAST:
+            break;
+        }
+
+        if (hostOff &&
+            def->cpu->mode == VIR_CPU_MODE_HOST_PASSTHROUGH &&
+            virQEMUCapsGet(qemuCaps, QEMU_CAPS_CPU_HOST_CACHE))
+            virBufferAddLit(&buf, ",host-cache-info=off");
+
+        if (l3Off &&
+            virQEMUCapsGet(qemuCaps, QEMU_CAPS_CPU_L3_CACHE))
+            virBufferAddLit(&buf, ",l3-cache=off");
+    }
+
     if (virBufferCheckError(&buf) < 0)
         goto cleanup;
 
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 00b0b4ac4..dcce9134c 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -2714,6 +2714,60 @@ qemuDomainDefCPUPostParse(virDomainDefPtr def)
     if (!def->cpu)
         return 0;
 
+    if (def->cpu->cache) {
+        virCPUCacheDefPtr cache = def->cpu->cache;
+
+        if (!ARCH_IS_X86(def->os.arch)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("CPU cache specification is not supported "
+                             "for '%s' architecture"),
+                           virArchToString(def->os.arch));
+            return -1;
+        }
+
+        switch (cache->mode) {
+        case VIR_CPU_CACHE_MODE_EMULATE:
+            if (cache->level != 3) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                               _("CPU cache mode '%s' can only be used with "
+                                 "level='3'"),
+                               virCPUCacheModeTypeToString(cache->mode));
+                return -1;
+            }
+            break;
+
+        case VIR_CPU_CACHE_MODE_PASSTHROUGH:
+            if (def->cpu->mode != VIR_CPU_MODE_HOST_PASSTHROUGH) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                               _("CPU cache mode '%s' can only be used with "
+                                 "'%s' CPUs"),
+                               virCPUCacheModeTypeToString(cache->mode),
+                               virCPUModeTypeToString(VIR_CPU_MODE_HOST_PASSTHROUGH));
+                return -1;
+            }
+
+            if (cache->level != -1) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                               _("unsupported CPU cache level for mode '%s'"),
+                               virCPUCacheModeTypeToString(cache->mode));
+                return -1;
+            }
+            break;
+
+        case VIR_CPU_CACHE_MODE_DISABLE:
+            if (cache->level != -1) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                               _("unsupported CPU cache level for mode '%s'"),
+                               virCPUCacheModeTypeToString(cache->mode));
+                return -1;
+            }
+            break;
+
+        case VIR_CPU_CACHE_MODE_LAST:
+            break;
+        }
+    }
+
     /* Nothing to be done if only CPU topology is specified. */
     if (def->cpu->mode == VIR_CPU_MODE_CUSTOM &&
         !def->cpu->model)
diff --git a/tests/qemucapabilitiesdata/caps_2.9.0.x86_64.xml b/tests/qemucapabilitiesdata/caps_2.9.0.x86_64.xml
index 6386c4ed0..8e417f47b 100644
--- a/tests/qemucapabilitiesdata/caps_2.9.0.x86_64.xml
+++ b/tests/qemucapabilitiesdata/caps_2.9.0.x86_64.xml
@@ -207,6 +207,8 @@
   <flag name='query-cpu-definitions'/>
   <flag name='block-write-threshold'/>
   <flag name='query-named-block-nodes'/>
+  <flag name='cpu-host-cache'/>
+  <flag name='cpu-l3-cache'/>
   <version>2008090</version>
   <kvmVersion>0</kvmVersion>
   <package> (v2.9.0-rc0-142-g940a8ce)</package>
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable.args b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable.args
new file mode 100644
index 000000000..b4976a53c
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable.args
@@ -0,0 +1,21 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-x86_64 \
+-name foo \
+-S \
+-M pc \
+-cpu host,host-cache-info=off,l3-cache=off \
+-m 214 \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-nographic \
+-nodefaults \
+-monitor unix:/tmp/lib/domain--1-foo/monitor.sock,server,nowait \
+-no-acpi \
+-boot c \
+-usb \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable.xml b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable.xml
new file mode 100644
index 000000000..e6f39951c
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-passthrough'>
+    <cache mode='disable'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable2.args b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable2.args
new file mode 100644
index 000000000..b024d8209
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable2.args
@@ -0,0 +1,21 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-x86_64 \
+-name foo \
+-S \
+-M pc \
+-cpu host \
+-m 214 \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-nographic \
+-nodefaults \
+-monitor unix:/tmp/lib/domain--1-foo/monitor.sock,server,nowait \
+-no-acpi \
+-boot c \
+-usb \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable2.xml b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable2.xml
new file mode 100644
index 000000000..e6f39951c
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable2.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-passthrough'>
+    <cache mode='disable'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable3.args b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable3.args
new file mode 100644
index 000000000..19a2e9609
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable3.args
@@ -0,0 +1,22 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-x86_64 \
+-name foo \
+-S \
+-M pc \
+-cpu core2duo,+ds,+acpi,+ss,+ht,+tm,+pbe,+ds_cpl,+vmx,+est,+tm2,+cx16,+xtpr,\
++lahf_lm,l3-cache=off \
+-m 214 \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-nographic \
+-nodefaults \
+-monitor unix:/tmp/lib/domain--1-foo/monitor.sock,server,nowait \
+-no-acpi \
+-boot c \
+-usb \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable3.xml b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable3.xml
new file mode 100644
index 000000000..17078a1e8
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-disable3.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-model'>
+    <cache mode='disable'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-emulate-l2.xml b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-emulate-l2.xml
new file mode 100644
index 000000000..4757e85ea
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-emulate-l2.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-model' check='full'>
+    <cache level='2' mode='emulate'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-emulate-l3.args b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-emulate-l3.args
new file mode 100644
index 000000000..31fbadaaf
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-emulate-l3.args
@@ -0,0 +1,21 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-x86_64 \
+-name foo \
+-S \
+-M pc \
+-cpu host,l3-cache=on,host-cache-info=off \
+-m 214 \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-nographic \
+-nodefaults \
+-monitor unix:/tmp/lib/domain--1-foo/monitor.sock,server,nowait \
+-no-acpi \
+-boot c \
+-usb \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-emulate-l3.xml b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-emulate-l3.xml
new file mode 100644
index 000000000..17019c673
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-emulate-l3.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-passthrough'>
+    <cache level='3' mode='emulate'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough-l3.xml b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough-l3.xml
new file mode 100644
index 000000000..3471115ea
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough-l3.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-passthrough'>
+    <cache level='3' mode='passthrough'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough.args b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough.args
new file mode 100644
index 000000000..fdc73b493
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough.args
@@ -0,0 +1,21 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-x86_64 \
+-name foo \
+-S \
+-M pc \
+-cpu host,host-cache-info=on,l3-cache=off \
+-m 214 \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-nographic \
+-nodefaults \
+-monitor unix:/tmp/lib/domain--1-foo/monitor.sock,server,nowait \
+-no-acpi \
+-boot c \
+-usb \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough.xml b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough.xml
new file mode 100644
index 000000000..74846fdd3
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-passthrough'>
+    <cache mode='passthrough'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.args b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.args
new file mode 100644
index 000000000..cf4c55ca3
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.args
@@ -0,0 +1,21 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-x86_64 \
+-name foo \
+-S \
+-M pc \
+-cpu host,host-cache-info=on \
+-m 214 \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-nographic \
+-nodefaults \
+-monitor unix:/tmp/lib/domain--1-foo/monitor.sock,server,nowait \
+-no-acpi \
+-boot c \
+-usb \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.xml b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.xml
new file mode 100644
index 000000000..74846fdd3
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-passthrough'>
+    <cache mode='passthrough'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough3.xml b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough3.xml
new file mode 100644
index 000000000..6ad65700b
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough3.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-model'>
+    <cache mode='passthrough'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
index c1b014b7d..15765fdfd 100644
--- a/tests/qemuxml2argvtest.c
+++ b/tests/qemuxml2argvtest.c
@@ -2513,6 +2513,22 @@ mymain(void)
     DO_TEST("cpu-check-default-partial", QEMU_CAPS_KVM);
     DO_TEST("cpu-check-default-partial2", QEMU_CAPS_KVM);
 
+    DO_TEST("cpu-cache-disable",
+            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE);
+    DO_TEST("cpu-cache-disable2",
+            QEMU_CAPS_KVM);
+    DO_TEST("cpu-cache-disable3",
+            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE);
+    DO_TEST("cpu-cache-passthrough",
+            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE);
+    DO_TEST("cpu-cache-passthrough2",
+            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE);
+    DO_TEST("cpu-cache-emulate-l3",
+            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE);
+    DO_TEST_PARSE_ERROR("cpu-cache-emulate-l2", QEMU_CAPS_KVM);
+    DO_TEST_PARSE_ERROR("cpu-cache-passthrough3", QEMU_CAPS_KVM);
+    DO_TEST_PARSE_ERROR("cpu-cache-passthrough-l3", QEMU_CAPS_KVM);
+
     qemuTestDriverFree(&driver);
 
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
-- 
2.12.2

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On Tue, Apr 25, 2017 at 20:48:45 +0200, Jiri Denemark wrote:
> This patch maps /domain/cpu/cache element into -cpu parameters:
> 
> - <cache mode='passthrough'/> is translated to host-cache-info=on
> - <cache level='3' mode='emulate'/> is transformed into l3-cache=on
> - <cache mode='disable'/> is turned in host-cache-info=off,l3-cache=off

host-cache-info=on,l3-cache=off is specifically invalid from qemu's
point of view?

> 
> Any other <cache> element is forbidden.
> 
> The tricky part is detecting whether QEMU supports the CPU properties.
> 
> The 'host-cache-info' property is introduced in v2.4.0-1389-ge265e3e480,
> earlier QEMU releases enabled host-cache-info by default and had no way
> to disable it. If the property is present, it defaults to 'off' for any
> QEMU until at least 2.9.0.
> 
> The 'l3-cache' property was introduced later by v2.7.0-200-g14c985cffa.
> Earlier versions worked as if l3-cache=off was passed. For any QEMU
> until at least 2.9.0 l3-cache is 'off' by default.
> 
> QEMU 2.9.0 was the first release which supports probing both properties
> by running device-list-properties with typename=host-x86_64-cpu. Older
> QEMU releases did not support device-list-properties command for CPU
> devices. Thus we can't really rely on probing them and we can just use
> query-cpu-model-expansion QMP command as a witness.
> 
> Because the cache property probing is only reliable for QEMU >= 2.9.0
> when both are already supported for quite a few releases, we let QEMU
> report an error if a specific cache mode is explicitly requested. Thea
> other mode (or both if a user requested CPU cache to be disabled) is
> explicitly turned off for QEMU >= 2.9.0 to avoid any surprises in case
> the QEMU defaults change. Any older QEMU already turns them off so not
> doing so explicitly does not make any harm.
> 
> Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
> ---

[...]

> diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
> index cc3e1f808..5dd18f3c5 100644
> --- a/src/qemu/qemu_capabilities.c
> +++ b/src/qemu/qemu_capabilities.c

[...]

> @@ -4787,6 +4789,12 @@ virQEMUCapsInitQMPMonitor(virQEMUCapsPtr qemuCaps,
>          virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_NVDIMM))
>          virQEMUCapsClear(qemuCaps, QEMU_CAPS_DEVICE_NVDIMM);
>  
> +    if (ARCH_IS_X86(qemuCaps->arch) &&
> +        virQEMUCapsGet(qemuCaps, QEMU_CAPS_QUERY_CPU_MODEL_EXPANSION)) {
> +        virQEMUCapsSet(qemuCaps, QEMU_CAPS_CPU_HOST_CACHE);
> +        virQEMUCapsSet(qemuCaps, QEMU_CAPS_CPU_L3_CACHE);

Is it really necessary to add both of them separately even if you set
them both at once?

> +    }
> +
>      ret = 0;
>   cleanup:
>      return ret;

[...]

> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> index 1116d2cd5..eb7404ead 100644
> --- a/src/qemu/qemu_command.c
> +++ b/src/qemu/qemu_command.c
> @@ -7063,6 +7063,43 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
>          have_cpu = true;
>      }
>  
> +    if (def->cpu && def->cpu->cache) {
> +        virCPUCacheDefPtr cache = def->cpu->cache;
> +        bool hostOff = false;
> +        bool l3Off = false;
> +
> +        if (!have_cpu)
> +            virBufferAdd(&buf, default_model, -1);

You need to set have_cpu to true after this.

> +
> +        switch (cache->mode) {
> +        case VIR_CPU_CACHE_MODE_EMULATE:
> +            virBufferAddLit(&buf, ",l3-cache=on");
> +            hostOff = true;
> +            break;
> +
> +        case VIR_CPU_CACHE_MODE_PASSTHROUGH:
> +            virBufferAddLit(&buf, ",host-cache-info=on");
> +            l3Off = true;
> +            break;
> +
> +        case VIR_CPU_CACHE_MODE_DISABLE:
> +            hostOff = l3Off = true;
> +            break;
> +
> +        case VIR_CPU_CACHE_MODE_LAST:
> +            break;
> +        }
> +
> +        if (hostOff &&
> +            def->cpu->mode == VIR_CPU_MODE_HOST_PASSTHROUGH &&
> +            virQEMUCapsGet(qemuCaps, QEMU_CAPS_CPU_HOST_CACHE))
> +            virBufferAddLit(&buf, ",host-cache-info=off");
> +
> +        if (l3Off &&
> +            virQEMUCapsGet(qemuCaps, QEMU_CAPS_CPU_L3_CACHE))
> +            virBufferAddLit(&buf, ",l3-cache=off");
> +    }
> +
>      if (virBufferCheckError(&buf) < 0)
>          goto cleanup;
>  

[...]

> diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.args b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.args
> new file mode 100644
> index 000000000..cf4c55ca3
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.args
> @@ -0,0 +1,21 @@
> +LC_ALL=C \
> +PATH=/bin \
> +HOME=/home/test \
> +USER=test \
> +LOGNAME=test \
> +QEMU_AUDIO_DRV=none \
> +/usr/bin/qemu-system-x86_64 \
> +-name foo \
> +-S \
> +-M pc \
> +-cpu host,host-cache-info=on \

This is impossible in real life since QEMU_CAPS_CPU_HOST_CACHE and
QEMU_CAPS_CPU_L3_CACHE are always defined together.

> +-m 214 \
> +-smp 1,sockets=1,cores=1,threads=1 \
> +-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
> +-nographic \
> +-nodefaults \
> +-monitor unix:/tmp/lib/domain--1-foo/monitor.sock,server,nowait \
> +-no-acpi \
> +-boot c \
> +-usb \
> +-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3

[...]

> diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
> index c1b014b7d..15765fdfd 100644
> --- a/tests/qemuxml2argvtest.c
> +++ b/tests/qemuxml2argvtest.c
> @@ -2513,6 +2513,22 @@ mymain(void)
>      DO_TEST("cpu-check-default-partial", QEMU_CAPS_KVM);
>      DO_TEST("cpu-check-default-partial2", QEMU_CAPS_KVM);
>  
> +    DO_TEST("cpu-cache-disable",
> +            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE);
> +    DO_TEST("cpu-cache-disable2",
> +            QEMU_CAPS_KVM);
> +    DO_TEST("cpu-cache-disable3",
> +            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE);
> +    DO_TEST("cpu-cache-passthrough",
> +            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE);
> +    DO_TEST("cpu-cache-passthrough2",
> +            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE);

This test is misleading, you don't get a config like this with this
code.

> +    DO_TEST("cpu-cache-emulate-l3",
> +            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE);
> +    DO_TEST_PARSE_ERROR("cpu-cache-emulate-l2", QEMU_CAPS_KVM);
> +    DO_TEST_PARSE_ERROR("cpu-cache-passthrough3", QEMU_CAPS_KVM);
> +    DO_TEST_PARSE_ERROR("cpu-cache-passthrough-l3", QEMU_CAPS_KVM);
> +
>      qemuTestDriverFree(&driver);
>  
>      return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;

ACK with the above things sorted out.
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On Thu, Apr 27, 2017 at 17:09:41 +0200, Peter Krempa wrote:
> On Tue, Apr 25, 2017 at 20:48:45 +0200, Jiri Denemark wrote:
> > This patch maps /domain/cpu/cache element into -cpu parameters:
> > 
> > - <cache mode='passthrough'/> is translated to host-cache-info=on
> > - <cache level='3' mode='emulate'/> is transformed into l3-cache=on
> > - <cache mode='disable'/> is turned in host-cache-info=off,l3-cache=off
> 
> host-cache-info=on,l3-cache=off is specifically invalid from qemu's
> point of view?

No. Libvirt will automatically add l3-cache=off to host-cache-info=on
and host-cache-info=off to l3-cache=on if it detects QEMU supports these
properties. Otherwise it will just blindly add the one explicitly
requested and let QEMU fail if it doesn't support it.

> > Any other <cache> element is forbidden.
> > 
> > The tricky part is detecting whether QEMU supports the CPU properties.
> > 
> > The 'host-cache-info' property is introduced in v2.4.0-1389-ge265e3e480,
> > earlier QEMU releases enabled host-cache-info by default and had no way
> > to disable it. If the property is present, it defaults to 'off' for any
> > QEMU until at least 2.9.0.
> > 
> > The 'l3-cache' property was introduced later by v2.7.0-200-g14c985cffa.
> > Earlier versions worked as if l3-cache=off was passed. For any QEMU
> > until at least 2.9.0 l3-cache is 'off' by default.
> > 
> > QEMU 2.9.0 was the first release which supports probing both properties
> > by running device-list-properties with typename=host-x86_64-cpu. Older
> > QEMU releases did not support device-list-properties command for CPU
> > devices. Thus we can't really rely on probing them and we can just use
> > query-cpu-model-expansion QMP command as a witness.
> > 
> > Because the cache property probing is only reliable for QEMU >= 2.9.0
> > when both are already supported for quite a few releases, we let QEMU
> > report an error if a specific cache mode is explicitly requested. Thea
> > other mode (or both if a user requested CPU cache to be disabled) is
> > explicitly turned off for QEMU >= 2.9.0 to avoid any surprises in case
> > the QEMU defaults change. Any older QEMU already turns them off so not
> > doing so explicitly does not make any harm.
> > 
> > Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
> > ---
> 
> [...]
> 
> > diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
> > index cc3e1f808..5dd18f3c5 100644
> > --- a/src/qemu/qemu_capabilities.c
> > +++ b/src/qemu/qemu_capabilities.c
> > @@ -4787,6 +4789,12 @@ virQEMUCapsInitQMPMonitor(virQEMUCapsPtr qemuCaps,
> >          virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_NVDIMM))
> >          virQEMUCapsClear(qemuCaps, QEMU_CAPS_DEVICE_NVDIMM);
> >  
> > +    if (ARCH_IS_X86(qemuCaps->arch) &&
> > +        virQEMUCapsGet(qemuCaps, QEMU_CAPS_QUERY_CPU_MODEL_EXPANSION)) {
> > +        virQEMUCapsSet(qemuCaps, QEMU_CAPS_CPU_HOST_CACHE);
> > +        virQEMUCapsSet(qemuCaps, QEMU_CAPS_CPU_L3_CACHE);
> 
> Is it really necessary to add both of them separately even if you set
> them both at once?

Hmm, I guess QEMU_CAPS_CPU_CACHE would be enough.

> > diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.args b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.args
> > new file mode 100644
> > index 000000000..cf4c55ca3
> > --- /dev/null
> > +++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.args
> > @@ -0,0 +1,21 @@
> > +LC_ALL=C \
> > +PATH=/bin \
> > +HOME=/home/test \
> > +USER=test \
> > +LOGNAME=test \
> > +QEMU_AUDIO_DRV=none \
> > +/usr/bin/qemu-system-x86_64 \
> > +-name foo \
> > +-S \
> > +-M pc \
> > +-cpu host,host-cache-info=on \
> 
> This is impossible in real life since QEMU_CAPS_CPU_HOST_CACHE and
> QEMU_CAPS_CPU_L3_CACHE are always defined together.

$cache=on is always added even if QEMU_CAPS_CPU_CACHE capability is not
set. Only the $cache=off parameters are influenced by the capability. In
other words, this is a real world command line generated for QEMU older
than 2.9.0.

> > diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
> > index c1b014b7d..15765fdfd 100644
> > --- a/tests/qemuxml2argvtest.c
> > +++ b/tests/qemuxml2argvtest.c
> > @@ -2513,6 +2513,22 @@ mymain(void)
> >      DO_TEST("cpu-check-default-partial", QEMU_CAPS_KVM);
> >      DO_TEST("cpu-check-default-partial2", QEMU_CAPS_KVM);
> >  
> > +    DO_TEST("cpu-cache-disable",
> > +            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE);
> > +    DO_TEST("cpu-cache-disable2",
> > +            QEMU_CAPS_KVM);
> > +    DO_TEST("cpu-cache-disable3",
> > +            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE);
> > +    DO_TEST("cpu-cache-passthrough",
> > +            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE);
> > +    DO_TEST("cpu-cache-passthrough2",
> > +            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE);
> 
> This test is misleading, you don't get a config like this with this
> code.

Oh right, only QEMU_CAPS_KVM should be set for this test.

> 
> > +    DO_TEST("cpu-cache-emulate-l3",
> > +            QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE);
> > +    DO_TEST_PARSE_ERROR("cpu-cache-emulate-l2", QEMU_CAPS_KVM);
> > +    DO_TEST_PARSE_ERROR("cpu-cache-passthrough3", QEMU_CAPS_KVM);
> > +    DO_TEST_PARSE_ERROR("cpu-cache-passthrough-l3", QEMU_CAPS_KVM);
> > +
> >      qemuTestDriverFree(&driver);
> >  
> >      return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
> 
> ACK with the above things sorted out.

Pushed with all the things sorted out. Thanks.

Jirka

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