Re: [Qemu-devel] [PATCH] target-i386: Remove POPCNT from qemu64 and qemu32 CPU models

[Paolo Bonzini <pbonzini@redhat.com>]

On 04/11/2015 16:35, Eduardo Habkost wrote:
> POPCNT is not available on Penryn and older and on Opteron_G2 and older,
> and we want to make the default CPU runnable in most hosts, so it won't
> be enabled by default in KVM mode.
> 
> We should eventually have all features supported by TCG enabled by
> default in TCG mode, but as we don't have a good mechanism today to
> ensure we have different defaults in KVM and TCG mode, disable POPCNT in
> the qemu64 and qemu32 CPU models entirely.
> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
> This patch needs to be applied after the series:
>   Subject: [PATCH v2 0/3] target-i386: Don't trigger CPUID warnings by
>            default in KVM mode (in most hosts)
> ---
>  include/hw/i386/pc.h | 10 ++++++++++
>  target-i386/cpu.c    |  4 ++--
>  2 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 8b54863..4bbc0ff 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -337,6 +337,16 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
>              .driver   = "qemu64" "-" TYPE_X86_CPU,\
>              .property = "abm",\
>              .value    = "on",\
> +        },\
> +        {\
> +            .driver   = "qemu64" "-" TYPE_X86_CPU,\
> +            .property = "popcnt",\
> +            .value    = "on",\
> +        },\
> +        {\
> +            .driver   = "qemu32" "-" TYPE_X86_CPU,\
> +            .property = "popcnt",\
> +            .value    = "on",\
>          },
>  
>  #define PC_COMPAT_2_3 \
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 35cd267..5a62ef5 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -671,7 +671,7 @@ static X86CPUDefinition builtin_x86_defs[] = {
>              CPUID_MTRR | CPUID_CLFLUSH | CPUID_MCA |
>              CPUID_PSE36,
>          .features[FEAT_1_ECX] =
> -            CPUID_EXT_SSE3 | CPUID_EXT_CX16 | CPUID_EXT_POPCNT,
> +            CPUID_EXT_SSE3 | CPUID_EXT_CX16,
>          .features[FEAT_8000_0001_EDX] =
>              CPUID_EXT2_LM | CPUID_EXT2_SYSCALL | CPUID_EXT2_NX,
>          .features[FEAT_8000_0001_ECX] =
> @@ -771,7 +771,7 @@ static X86CPUDefinition builtin_x86_defs[] = {
>          .features[FEAT_1_EDX] =
>              PPRO_FEATURES,
>          .features[FEAT_1_ECX] =
> -            CPUID_EXT_SSE3 | CPUID_EXT_POPCNT,
> +            CPUID_EXT_SSE3,
>          .xlevel = 0x80000004,
>      },
>      {
> 

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>