Re: [Qemu-devel] [PATCH] i386: Support "-cpu host" on TCG too

["Richard W.M. Jones" <rjones@redhat.com>]

On Mon, Jan 16, 2017 at 05:54:52PM -0200, Eduardo Habkost wrote:
> Change the meaning of "-cpu host" to "enable all features
> supported by the accelerator in the current host", so that it can
> be used to enable/query all features supported by TCG.
> 
> To make sure "host" is still at the end of the list in "-cpu
> help", add a "ordering" field that will be used when sorting the
> CPU model list.
> 
> Cc: Richard Henderson <rth@twiddle.net>
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
>  target/i386/cpu-qom.h |  4 ++--
>  target/i386/cpu.c     | 26 +++++---------------------
>  2 files changed, 7 insertions(+), 23 deletions(-)
> 
> diff --git a/target/i386/cpu-qom.h b/target/i386/cpu-qom.h
> index 8cd607e9a2..75618919e3 100644
> --- a/target/i386/cpu-qom.h
> +++ b/target/i386/cpu-qom.h
> @@ -47,7 +47,7 @@ typedef struct X86CPUDefinition X86CPUDefinition;
>  /**
>   * X86CPUClass:
>   * @cpu_def: CPU model definition
> - * @kvm_required: Whether CPU model requires KVM to be enabled.
> + * @ordering: Ordering on the "-cpu help" CPU model list.
>   * @migration_safe: See CpuDefinitionInfo::migration_safe
>   * @parent_realize: The parent class' realize handler.
>   * @parent_reset: The parent class' reset handler.
> @@ -62,7 +62,7 @@ typedef struct X86CPUClass {
>      /* Should be eventually replaced by subclass-specific property defaults. */
>      X86CPUDefinition *cpu_def;
>  
> -    bool kvm_required;
> +    int ordering;
>      bool migration_safe;
>  
>      /* Optional description of CPU model.
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index ec6eaf215c..e0ca8c0288 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -1549,7 +1549,7 @@ static void host_x86_cpu_class_init(ObjectClass *oc, void *data)
>      X86CPUClass *xcc = X86_CPU_CLASS(oc);
>      uint32_t eax = 0, ebx = 0, ecx = 0, edx = 0;
>  
> -    xcc->kvm_required = true;
> +    xcc->ordering = 9; /* Show it last on "-cpu help" */
>  
>      host_cpuid(0x0, 0, &eax, &ebx, &ecx, &edx);
>      x86_cpu_vendor_words2str(host_cpudef.vendor, ebx, edx, ecx);
> @@ -1563,8 +1563,7 @@ static void host_x86_cpu_class_init(ObjectClass *oc, void *data)
>  
>      xcc->cpu_def = &host_cpudef;
>      xcc->model_description =
> -        "KVM processor with all supported host features "
> -        "(only available in KVM mode)";
> +        "Enables all features supported by the accelerator in the current host";
>  
>      /* level, xlevel, xlevel2, and the feature words are initialized on
>       * instance_init, because they require KVM to be initialized.
> @@ -2075,13 +2074,6 @@ static void x86_cpu_class_check_missing_features(X86CPUClass *xcc,
>      Error *err = NULL;
>      strList **next = missing_feats;
>  
> -    if (xcc->kvm_required && !kvm_enabled()) {
> -        strList *new = g_new0(strList, 1);
> -        new->value = g_strdup("kvm");;
> -        *missing_feats = new;
> -        return;
> -    }
> -
>      xc = X86_CPU(object_new(object_class_get_name(OBJECT_CLASS(xcc))));
>  
>      x86_cpu_load_features(xc, &err);
> @@ -2129,7 +2121,7 @@ static void listflags(FILE *f, fprintf_function print, const char **featureset)
>      }
>  }
>  
> -/* Sort alphabetically by type name, listing kvm_required models last. */
> +/* Sort alphabetically by type name, respecting X86CPUClass::ordering. */
>  static gint x86_cpu_list_compare(gconstpointer a, gconstpointer b)
>  {
>      ObjectClass *class_a = (ObjectClass *)a;
> @@ -2138,9 +2130,8 @@ static gint x86_cpu_list_compare(gconstpointer a, gconstpointer b)
>      X86CPUClass *cc_b = X86_CPU_CLASS(class_b);
>      const char *name_a, *name_b;
>  
> -    if (cc_a->kvm_required != cc_b->kvm_required) {
> -        /* kvm_required items go last */
> -        return cc_a->kvm_required ? 1 : -1;
> +    if (cc_a->ordering != cc_b->ordering) {
> +        return cc_a->ordering - cc_b->ordering;
>      } else {
>          name_a = object_class_get_name(class_a);
>          name_b = object_class_get_name(class_b);
> @@ -3191,13 +3182,6 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
>      Error *local_err = NULL;
>      static bool ht_warned;
>  
> -    if (xcc->kvm_required && !kvm_enabled()) {
> -        char *name = x86_cpu_class_get_model_name(xcc);
> -        error_setg(&local_err, "CPU model '%s' requires KVM", name);
> -        g_free(name);
> -        goto out;
> -    }
> -
>      if (cpu->apic_id == UNASSIGNED_APIC_ID) {
>          error_setg(errp, "apic-id property was not initialized properly");
>          return;

FYI libvirt will also need changing.  Currently it reports:

  Original error from libvirt: unsupported configuration: CPU mode 'host-passthrough' for x86_64 qemu domain on x86_64 host is not supported by hypervisor [code=67 int1=-1]

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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