Re: [PATCH v2 4/8] x86: Add XFD faulting bit for state components

[David Edmondson]

On Wednesday, 2022-02-16 at 22:04:30 -08, Yang Zhong wrote:

> From: Jing Liu <jing2.liu@intel.com>
>
> Intel introduces XFD faulting mechanism for extended
> XSAVE features to dynamically enable the features in
> runtime. If CPUID (EAX=0Dh, ECX=n, n>1).ECX[2] is set
> as 1, it indicates support for XFD faulting of this
> state component.
>
> Signed-off-by: Jing Liu <jing2.liu@intel.com>
> Signed-off-by: Yang Zhong <yang.zhong@intel.com>

Small comment below...

Reviewed-by: David Edmondson <david.edmondson@oracle.com>

> ---
>  target/i386/cpu.h | 2 ++
>  target/i386/cpu.c | 3 ++-
>  2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index d4ad0f56bd..f7fc2e97a6 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -558,8 +558,10 @@ typedef enum X86Seg {
>  #define ARCH_REQ_XCOMP_GUEST_PERM       0x1025
>
>  #define ESA_FEATURE_ALIGN64_BIT         1
> +#define ESA_FEATURE_XFD_BIT             2
>
>  #define ESA_FEATURE_ALIGN64_MASK        (1U << ESA_FEATURE_ALIGN64_BIT)
> +#define ESA_FEATURE_XFD_MASK            (1U << ESA_FEATURE_XFD_BIT)
>
>  /* CPUID feature words */
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 377d993438..5a7ee8c7e1 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -5497,7 +5497,8 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
> uint32_t count,
>                  const ExtSaveArea *esa = &x86_ext_save_areas[count];
>                  *eax = esa->size;
>                  *ebx = esa->offset;
> -                *ecx = esa->ecx & ESA_FEATURE_ALIGN64_MASK;
> +                *ecx = (esa->ecx & ESA_FEATURE_ALIGN64_MASK) |
> +                       (esa->ecx & ESA_FEATURE_XFD_MASK);

Is:

                *ecx = esa->ecx &
                       (ESA_FEATURE_ALIGN64_MASK | ESA_FEATURE_XFD_MASK);

not more usual?

>              }
>          }
>          break;

dme.
-- 
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