Re: [PATCH 4/6] qemu-caps: Get host model directly from Qemu when available

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On Mon, Nov 21, 2016 at 14:11:54 -0500, Jason J. Herne wrote:
> From: "Collin L. Walling" <walling@xxxxxxxxxxxxxxxxxx>
> 
> When qmp query-cpu-model-expansion is available probe Qemu for its view of the
> host model. In kvm environments this can provide a more complete view of the
> host model because features supported by Qemu and Kvm can be considered.
> 
> Signed-off-by: Collin L. Walling <walling@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Jason J. Herne <jjherne@xxxxxxxxxxxxxxxxxx>
> ---
>  src/qemu/qemu_capabilities.c | 109 +++++++++++++++++++++++++++++++++++++++++--
>  src/qemu/qemu_capabilities.h |   1 +
>  2 files changed, 105 insertions(+), 5 deletions(-)
> 
> diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
> index cfd090c..b2c70cf 100644
> --- a/src/qemu/qemu_capabilities.c
> +++ b/src/qemu/qemu_capabilities.c
> @@ -352,6 +352,7 @@ VIR_ENUM_IMPL(virQEMUCaps, QEMU_CAPS_LAST,
>                "ivshmem-doorbell", /* 240 */
>                "query-qmp-schema",
>                "gluster.debug_level",
> +              "query-cpu-model-expansion",
>      );
>  
>  
> @@ -394,6 +395,8 @@ struct _virQEMUCaps {
>      size_t ngicCapabilities;
>      virGICCapability *gicCapabilities;
>  
> +    qemuMonitorCPUModelInfoPtr hostCPUModelInfo;
> +
>      /* Anything below is not stored in the cache since the values are
>       * re-computed from the other fields or external data sources every
>       * time we probe QEMU or load the results from the cache.
> @@ -1493,7 +1496,8 @@ struct virQEMUCapsStringFlags virQEMUCapsCommands[] = {
>      { "rtc-reset-reinjection", QEMU_CAPS_RTC_RESET_REINJECTION },
>      { "migrate-incoming", QEMU_CAPS_INCOMING_DEFER },
>      { "query-hotpluggable-cpus", QEMU_CAPS_QUERY_HOTPLUGGABLE_CPUS },
> -    { "query-qmp-schema", QEMU_CAPS_QUERY_QMP_SCHEMA }
> +    { "query-qmp-schema", QEMU_CAPS_QUERY_QMP_SCHEMA },
> +    { "query-cpu-model-expansion", QEMU_CAPS_QUERY_CPU_MODEL_EXPANSION},
>  };
>  
>  struct virQEMUCapsStringFlags virQEMUCapsMigration[] = {
> @@ -2131,6 +2135,10 @@ virQEMUCapsPtr virQEMUCapsNewCopy(virQEMUCapsPtr qemuCaps)
>          !(ret->hostCPUModel = virCPUDefCopy(qemuCaps->hostCPUModel)))
>          goto error;
>  
> +    if (qemuCaps->hostCPUModelInfo &&
> +        !(ret->hostCPUModelInfo = qemuMonitorCPUModelInfoCopy(qemuCaps->hostCPUModelInfo)))
> +        goto error;
> +
>      if (VIR_ALLOC_N(ret->machineTypes, qemuCaps->nmachineTypes) < 0)
>          goto error;
>      ret->nmachineTypes = qemuCaps->nmachineTypes;
> @@ -2741,6 +2749,18 @@ virQEMUCapsProbeQMPCPUDefinitions(virQEMUCapsPtr qemuCaps,
>      return ret;
>  }
>  
> +static int
> +virQEMUCapsProbeQMPHostCPU(virQEMUCapsPtr qemuCaps,
> +                                qemuMonitorPtr mon)

The indentation is a bit off here.

> +{
> +    if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_QUERY_CPU_MODEL_EXPANSION) ||
> +        !virQEMUCapsGet(qemuCaps, QEMU_CAPS_KVM))
> +        return 0;
> +
> +    return qemuMonitorGetCPUModelExpansion(mon, "static", "host",
> +                                           &qemuCaps->hostCPUModelInfo);
> +}
> +
>  struct tpmTypeToCaps {
>      int type;
>      virQEMUCapsFlags caps;
> @@ -2966,6 +2986,29 @@ virQEMUCapsCPUFilterFeatures(const char *name,
>  }
>  
>  
> +static int
> +virQEMUCapsCopyModelFromQEMU(virCPUDefPtr dst,
> +                             const qemuMonitorCPUModelInfo *modelInfo)
> +{
> +    size_t i;
> +
> +    if (VIR_STRDUP(dst->model, modelInfo->name) < 0 ||
> +        VIR_ALLOC_N(dst->features, modelInfo->nprops) < 0)
> +        return -1;
> +    dst->nfeatures_max = modelInfo->nprops;
> +    dst->nfeatures = 0;
> +
> +    for (i = 0; i < modelInfo->nprops; i++) {
> +        if (VIR_STRDUP(dst->features[i].name, modelInfo->props[i].name) < 0)
> +            return -1;
> +        dst->features[i].policy = VIR_CPU_FEATURE_REQUIRE;

The qemuMonitorCPUModelInfo structure contains "bool supported" for each
feature, so I think the policy should depend on it:

    if (modelInfo->props[i].supported)
        dst->features[i].policy = VIR_CPU_FEATURE_REQUIRE;
    else
        dst->features[i].policy = VIR_CPU_FEATURE_DISABLE;

> +        dst->nfeatures++;
> +    }
> +
> +    return 0;
> +}

I'm a bit afraid it's not going to be this easy for x86_64 and I think
we should make sure this code is not used for setting host CPU models on
architectures we did not check the code with. In other words, I'd expect
this function to return -1 on error, 0 on success, and 1 when the caller
should fall back to copying host CPU model from caps->host (this would
currently happen for arch != s390 or if qemuCaps->hostCPUModelInfo is
NULL). Which means the function could just take qemuCaps pointer.

> +
> +
>  void
>  virQEMUCapsInitHostCPUModel(virQEMUCapsPtr qemuCaps,
>                              virCapsPtr caps)
> @@ -2978,7 +3021,8 @@ virQEMUCapsInitHostCPUModel(virQEMUCapsPtr qemuCaps,
>      if (!virQEMUCapsGuestIsNative(caps->host.arch, qemuCaps->arch))
>          goto error;
>  
> -    if (caps->host.cpu && caps->host.cpu->model) {
> +    if ((caps->host.cpu && caps->host.cpu->model)
> +        || qemuCaps->hostCPUModelInfo) {
>          if (VIR_ALLOC(cpu) < 0)
>              goto error;
>  

And here, we could just unconditionally initialize cpu, call
virQEMUCapsCopyModelFromQEMU, and fall back to the existing code.

> @@ -2987,9 +3031,14 @@ virQEMUCapsInitHostCPUModel(virQEMUCapsPtr qemuCaps,
>          cpu->mode = VIR_CPU_MODE_CUSTOM;
>          cpu->match = VIR_CPU_MATCH_EXACT;
>  
> -        if (virCPUDefCopyModelFilter(cpu, caps->host.cpu, true,
> -                                     virQEMUCapsCPUFilterFeatures, NULL) < 0)
> -            goto error;
> +        if (qemuCaps->hostCPUModelInfo) {
> +            if (virQEMUCapsCopyModelFromQEMU(cpu, qemuCaps->hostCPUModelInfo) < 0)
> +                goto error;
> +        } else {
> +            if (virCPUDefCopyModelFilter(cpu, caps->host.cpu, true,
> +                                         virQEMUCapsCPUFilterFeatures, NULL) < 0)
> +                goto error;
> +        }
>      }
>  
>      qemuCaps->hostCPUModel = cpu;
> @@ -3031,6 +3080,7 @@ virQEMUCapsLoadCache(virCapsPtr caps,
>      size_t i;
>      int n;
>      xmlNodePtr *nodes = NULL;
> +    xmlNodePtr node = NULL;
>      xmlXPathContextPtr ctxt = NULL;
>      char *str = NULL;
>      long long int l;
> @@ -3130,6 +3180,37 @@ virQEMUCapsLoadCache(virCapsPtr caps,
>      }
>      VIR_FREE(str);
>  
> +    if ((node = virXPathNode("./host/cpu", ctxt)) != NULL) {
> +        xmlNodePtr oldnode = ctxt->node;
> +        ctxt->node = node;
> +        if ((str = virXPathString("string(./model)", ctxt))) {
> +            if (VIR_ALLOC(qemuCaps->hostCPUModelInfo) < 0)
> +                goto cleanup;

So in case ./model element didn't exist (which would actually be an
error), qemuCaps->hostCPUModelInfo would happily be accessed even though
it was never allocated.

> +            if (VIR_STRDUP(qemuCaps->hostCPUModelInfo->name, str) < 0)
> +                goto cleanup;
> +        }
> +        if ((n = virXPathNodeSet("./feature", ctxt, &nodes)) > 0) {
> +            if (VIR_ALLOC_N(qemuCaps->hostCPUModelInfo->props, n) < 0)
> +                goto cleanup;
> +            qemuCaps->hostCPUModelInfo->nprops = n;
> +            for (i = 0; i < n; i++) {
> +                if (!(str = virXMLPropString(nodes[i], "name"))) {
> +                    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> +                                   _("missing name for a host CPU model"
> +                                     " feature in QEMU capabilities cache"));
> +                    goto cleanup;
> +                }
> +                if (VIR_STRDUP(qemuCaps->hostCPUModelInfo->props[i].name, str) < 0)
> +                    goto cleanup;
> +                qemuCaps->hostCPUModelInfo->props[i].supported = true;
> +            }
> +        }
> +        ctxt->node = oldnode;
> +        node = NULL;
> +        VIR_FREE(str);
> +    }
> +    VIR_FREE(nodes);
> +

Please, move this code into a new function. And I think

    <host>
        <cpu>
            <model>Name</model>
            <feature name='Feat'/>
            ...
        </cpu>
    </host>

is a bit too verbose and nested. What about

    <hostCPU model='Name'>
        <feature name='Feat' supported='yes|no'/>
        ...
    </hostCPU>

Which shows another issue with this code. It expects all features are
supported. We also need to store and load the value of
props[i].supported.

>      if ((n = virXPathNodeSet("./cpu", ctxt, &nodes)) < 0) {
>          virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>                         _("failed to parse qemu capabilities cpus"));
> @@ -3310,6 +3391,23 @@ virQEMUCapsFormatCache(virQEMUCapsPtr qemuCaps,
>      virBufferAsprintf(&buf, "<arch>%s</arch>\n",
>                        virArchToString(qemuCaps->arch));
>  
> +    if (qemuCaps->hostCPUModelInfo) {
> +        virBufferAddLit(&buf, "<host>\n");
> +        virBufferAdjustIndent(&buf, 2);
> +        virBufferAddLit(&buf, "<cpu>\n");
> +        virBufferAdjustIndent(&buf, 2);
> +        virBufferAsprintf(&buf, "<model>%s</model>\n",
> +                          qemuCaps->hostCPUModelInfo->name);
> +        for (i = 0; i < qemuCaps->hostCPUModelInfo->nprops; i++) {
> +            virBufferAsprintf(&buf, "<feature name='%s'/>\n",
> +                              qemuCaps->hostCPUModelInfo->props[i].name);
> +        }
> +        virBufferAdjustIndent(&buf, -2);
> +        virBufferAddLit(&buf, "</cpu>\n");
> +        virBufferAdjustIndent(&buf, -2);
> +        virBufferAddLit(&buf, "</host>\n");
> +    }
> +

And move this into a new function too.

>      if (qemuCaps->cpuDefinitions) {
>          for (i = 0; i < qemuCaps->cpuDefinitions->nmodels; i++) {
>              virDomainCapsCPUModelPtr cpu = qemuCaps->cpuDefinitions->models + i;
> @@ -3998,6 +4096,7 @@ virQEMUCapsInitQMPMonitor(virQEMUCapsPtr qemuCaps,
>          goto cleanup;
>      if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_QUERY_QMP_SCHEMA) &&
>          virQEMUCapsProbeQMPSchemaCapabilities(qemuCaps, mon) < 0)
> +    if (virQEMUCapsProbeQMPHostCPU(qemuCaps, mon) < 0)
>          goto cleanup;

Looks like wrong conflict resolution during rebase.

>      /* 'intel-iommu' shows up as a device since 2.2.0, but can
> diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
> index 9163572..82e1561 100644
> --- a/src/qemu/qemu_capabilities.h
> +++ b/src/qemu/qemu_capabilities.h
> @@ -387,6 +387,7 @@ typedef enum {
>      QEMU_CAPS_DEVICE_IVSHMEM_DOORBELL, /* -device ivshmem-doorbell */
>      QEMU_CAPS_QUERY_QMP_SCHEMA, /* query-qmp-schema command */
>      QEMU_CAPS_GLUSTER_DEBUG_LEVEL, /* -drive gluster.debug_level={0..9} */
> +    QEMU_CAPS_QUERY_CPU_MODEL_EXPANSION, /* qmp query-cpu-model-expansion */
>  
>      QEMU_CAPS_LAST /* this must always be the last item */
>  } virQEMUCapsFlags;

Jirka

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