conf: define a new "maximum" CPU mode

For hardware virtualization this is functionally identical to the
existing host-passthrough mode so the same caveats apply.

For emulated guest this exposes the maximum featureset supported by
the emulator. Note that despite being emulated this is not guaranteed
to be migration safe, especially if different emulator software versions
are used on each host.

Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index aa7ea6125823457925d08a57327bd48af4d4560b..2493be595fd85d63e60622e4fd8cf7a1039302d1 100644 (file)
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -1226,6 +1226,13 @@ following collection of elements. :since:`Since 0.7.5`
      <feature policy='disable' name='lahf_lm'/>
    ...
 
+::
+
+   <cpu mode='maximum' migratable='off'>
+     <cache mode='passthrough'/>
+     <feature policy='disable' name='lahf_lm'/>
+   ...
+
 In case no restrictions need to be put on CPU model and its features, a simpler
 ``cpu`` element can be used. :since:`Since 0.7.6`
 
@@ -1351,6 +1358,18 @@ In case no restrictions need to be put on CPU model and its features, a simpler
       another host safer: even with ``migratable='on'`` migration will be
       dangerous unless both hosts are identical as described above.
 
+   ``maximum``
+      When running a guest with hardware virtualization this CPU model is
+      functionally identical to ``host-passthrough``, so refer to the docs
+      above.
+
+      When running a guest with CPU emulation, this CPU model will enable
+      the maximum set of features that the emulation engine is able to support.
+      Note that even with ``migratable='on'`` migration will be dangerous
+      unless both hosts are running identical versions of the emulation code.
+
+      :since:`Since 7.1.0` with the QEMU driver.
+
    Both ``host-model`` and ``host-passthrough`` modes make sense when a domain
    can run directly on the host CPUs (for example, domains with type ``kvm``).
    The actual host CPU is irrelevant for domains with emulated virtual CPUs
@@ -1358,6 +1377,11 @@ In case no restrictions need to be put on CPU model and its features, a simpler
    ``host-model`` may be implemented even for domains running on emulated CPUs
    in which case the best CPU the hypervisor is able to emulate may be used
    rather then trying to mimic the host CPU model.
+
+   If an application does not care about a specific CPU, just wants the
+   best featureset without a need for migration compatibility, the
+   ``maximum`` model is a good choice on hypervisors where it is available.
+
 ``model``
    The content of the ``model`` element specifies CPU model requested by the
    guest. The list of available CPU models and their definition can be found in

diff --git a/src/conf/cpu_conf.c b/src/conf/cpu_conf.c
index f98b0a0eb3d9c6ae676eeb6d7ee314c25e4032b5..eb4bfbbcfa1e97c784a98fadd414afdb3aa3eaed 100644 (file)
--- a/src/conf/cpu_conf.c
+++ b/src/conf/cpu_conf.c
@@ -44,6 +44,7 @@ VIR_ENUM_IMPL(virCPUMode,
               "custom",
               "host-model",
               "host-passthrough",
+              "maximum",
 );
 
 VIR_ENUM_IMPL(virCPUMatch,
@@ -402,10 +403,11 @@ virCPUDefParseXML(xmlXPathContextPtr ctxt,
     if ((migratable = virXMLPropString(ctxt->node, "migratable"))) {
         int val;
 
-        if (def->mode != VIR_CPU_MODE_HOST_PASSTHROUGH) {
+        if (def->mode != VIR_CPU_MODE_HOST_PASSTHROUGH &&
+            def->mode != VIR_CPU_MODE_MAXIMUM) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                            _("Attribute migratable is only allowed for "
-                             "host-passthrough CPU"));
+                             "'host-passthrough' / 'maximum' CPU mode"));
             return -1;
         }
 
@@ -500,7 +502,8 @@ virCPUDefParseXML(xmlXPathContextPtr ctxt,
     }
 
     if (def->type == VIR_CPU_TYPE_GUEST &&
-        def->mode != VIR_CPU_MODE_HOST_PASSTHROUGH) {
+        def->mode != VIR_CPU_MODE_HOST_PASSTHROUGH &&
+        def->mode != VIR_CPU_MODE_MAXIMUM) {
 
         if ((fallback = virXPathString("string(./model[1]/@fallback)", ctxt))) {
             if ((def->fallback = virCPUFallbackTypeFromString(fallback)) < 0) {
@@ -727,7 +730,9 @@ virCPUDefFormatBufFull(virBufferPtr buf,
                               virCPUCheckTypeToString(def->check));
         }
 
-        if (def->mode == VIR_CPU_MODE_HOST_PASSTHROUGH && def->migratable) {
+        if ((def->mode == VIR_CPU_MODE_HOST_PASSTHROUGH ||
+             def->mode == VIR_CPU_MODE_MAXIMUM) &&
+            def->migratable) {
             virBufferAsprintf(&attributeBuf, " migratable='%s'",
                               virTristateSwitchTypeToString(def->migratable));
         }

diff --git a/src/conf/cpu_conf.h b/src/conf/cpu_conf.h
index b744b06c2d454279a26939a00ad3dea885d0fe78..7ab198d3708e2a10998609bd708d7cb11f4816bd 100644 (file)
--- a/src/conf/cpu_conf.h
+++ b/src/conf/cpu_conf.h
@@ -44,6 +44,7 @@ typedef enum {
     VIR_CPU_MODE_CUSTOM,
     VIR_CPU_MODE_HOST_MODEL,
     VIR_CPU_MODE_HOST_PASSTHROUGH,
+    VIR_CPU_MODE_MAXIMUM,
 
     VIR_CPU_MODE_LAST
 } virCPUMode;

diff --git a/src/cpu/cpu.c b/src/cpu/cpu.c
index 44094bd0dff3ba575dcde1ff111d0429b9df4242..6ff88d6a9f95b28b62aa329b84c8c67783fc8895 100644 (file)
--- a/src/cpu/cpu.c
+++ b/src/cpu/cpu.c
@@ -563,6 +563,7 @@ virCPUUpdate(virArch arch,
 
     switch ((virCPUMode) guest->mode) {
     case VIR_CPU_MODE_HOST_PASSTHROUGH:
+    case VIR_CPU_MODE_MAXIMUM:
         return 0;
 
     case VIR_CPU_MODE_HOST_MODEL:

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index ebd660788850ae0e2725aff1793669bd8c08fe81..fb302c8e0c59fa19ca88c1edbeca7aed2344a68c 100644 (file)
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -2334,6 +2334,7 @@ virQEMUCapsIsCPUModeSupported(virQEMUCapsPtr qemuCaps,
         cpus = virQEMUCapsGetAccel(qemuCaps, type)->cpuModels;
         return cpus && cpus->ncpus > 0;
 
+    case VIR_CPU_MODE_MAXIMUM:
     case VIR_CPU_MODE_LAST:
         break;
     }

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 92036d26c0a67f8c873b71c810c769d58dc3c317..059563d92f8ac1048553a28fed705c6546b1658d 100644 (file)
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -6356,6 +6356,7 @@ qemuBuildCpuModelArgStr(virQEMUDriverPtr driver,
         virBufferAdd(buf, cpu->model, -1);
         break;
 
+    case VIR_CPU_MODE_MAXIMUM:
     case VIR_CPU_MODE_LAST:
         break;
     }

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 0f09e321fb68cf655bacdce7919f3b7199d13ad6..d89aea340bb1682fb4b27ded1a9d76b686477c28 100644 (file)
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -4151,6 +4151,7 @@ qemuDomainDefCPUPostParse(virDomainDefPtr def,
             def->cpu->check = VIR_CPU_CHECK_PARTIAL;
         break;
 
+    case VIR_CPU_MODE_MAXIMUM:
     case VIR_CPU_MODE_LAST:
         break;
     }

diff --git a/src/qemu/qemu_validate.c b/src/qemu/qemu_validate.c
index 78e80b791904bbc8c8a835f113a3fec1f884429d..bf4ac19104abee9d1409bad543a2d19cf239c930 100644 (file)
--- a/src/qemu/qemu_validate.c
+++ b/src/qemu/qemu_validate.c
@@ -396,6 +396,7 @@ qemuValidateDomainDefCpu(virQEMUDriverPtr driver,
          * CUSTOM.
          */
         break;
+    case VIR_CPU_MODE_MAXIMUM:
     case VIR_CPU_MODE_CUSTOM:
     case VIR_CPU_MODE_LAST:
         break;