Re: [Xen-devel] [PATCH V4 3/4] x86/xsaves: enable xsaves/xrstors for hvm guest

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 25/08/15 11:54, Shuai Ruan wrote:
> This patch enables xsaves for hvm guest, includes:
> 1.handle xsaves vmcs init and vmexit.
> 2.add logic to write/read the XSS msr.
>
> Signed-off-by: Shuai Ruan <shuai.ruan@xxxxxxxxxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, given two
corrections...

> ---
>  xen/arch/x86/hvm/hvm.c             | 43 
> ++++++++++++++++++++++++++++++++++++++
>  xen/arch/x86/hvm/vmx/vmcs.c        |  6 ++++--
>  xen/arch/x86/hvm/vmx/vmx.c         | 20 ++++++++++++++++++
>  xen/arch/x86/xstate.c              |  4 ++--
>  xen/include/asm-x86/hvm/vmx/vmcs.h |  7 +++++++
>  xen/include/asm-x86/hvm/vmx/vmx.h  |  2 ++
>  xen/include/asm-x86/xstate.h       |  1 +
>  7 files changed, 79 insertions(+), 4 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index dc444ac..57612de 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -4540,6 +4540,33 @@ void hvm_cpuid(unsigned int input, unsigned int *eax, 
> unsigned int *ebx,
>                      *ebx = _eax + _ebx;
>              }
>          }
> +        if ( count == 1 )
> +        {
> +            if ( cpu_has_xsaves )
> +            {
> +                *ebx = XSTATE_AREA_MIN_SIZE;
> +                if ( v->arch.xcr0 | v->arch.msr_ia32_xss )
> +                    for ( sub_leaf = 2; sub_leaf < 63; sub_leaf++ )
> +                    {
> +                        if ( !((v->arch.xcr0 | v->arch.msr_ia32_xss)
> +                        & (1ULL << sub_leaf)) )

Stray hard tabs.

> @@ -4771,6 +4804,16 @@ int hvm_msr_write_intercept(unsigned int msr, uint64_t 
> msr_content,
>             return X86EMUL_EXCEPTION;
>          break;
>  
> +    case MSR_IA32_XSS:
> +     /*
> +      * skylake only support bit 8 , but it is
> +      * not support in xen.
> +      */

I would alter this comment to

/* No XSS features currently supported for guests. */

The skylake bits are covered by cpu_has_xsaves.

~Andrew

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