Re: [Xen-devel] [PATCH 2/2] x86/xsave: use alternative asm on xsave side.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.02.16 at 08:11, <shuai.ruan@xxxxxxxxxxxxxxx> wrote:
> --- a/xen/arch/x86/xstate.c
> +++ b/xen/arch/x86/xstate.c
> @@ -248,24 +248,26 @@ void xsave(struct vcpu *v, uint64_t mask)
>      uint32_t hmask = mask >> 32;
>      uint32_t lmask = mask;
>      int word_size = mask & XSTATE_FP ? (cpu_has_fpu_sel ? 8 : 0) : -1;
> +#define XSAVE(pfx) \
> +        alternative_io_3(".byte " pfx "0x0f,0xae,0x27\n", \
> +                         ".byte " pfx "0x0f,0xae,0x37\n", \
> +                         X86_FEATURE_XSAVEOPT, \
> +                         ".byte " pfx "0x0f,0xc7,0x27\n", \
> +                         X86_FEATURE_XSAVEC, \
> +                         ".byte " pfx "0x0f,0xc7,0x37\n", \
> +                         X86_FEATURE_XSAVES, \
> +                         "=m" (*ptr), \
> +                         "a" (lmask), "d" (hmask), "D" (ptr))
>  
>      if ( word_size <= 0 || !is_pv_32bit_vcpu(v) )
>      {
>          typeof(ptr->fpu_sse.fip.sel) fcs = ptr->fpu_sse.fip.sel;
>          typeof(ptr->fpu_sse.fdp.sel) fds = ptr->fpu_sse.fdp.sel;
>  
> -        if ( cpu_has_xsaves )
> -            asm volatile ( ".byte 0x48,0x0f,0xc7,0x2f"
> -                           : "=m" (*ptr)
> -                           : "a" (lmask), "d" (hmask), "D" (ptr) );
> -        else if ( cpu_has_xsavec )
> -            asm volatile ( ".byte 0x48,0x0f,0xc7,0x27"
> -                           : "=m" (*ptr)
> -                           : "a" (lmask), "d" (hmask), "D" (ptr) );
> -        else if ( cpu_has_xsaveopt )
> +        if ( cpu_has_xsaveopt || cpu_has_xsaves )
>          {
>              /*
> -             * xsaveopt may not write the FPU portion even when the 
> respective
> +             * xsaveopt/xsaves may not write the FPU portion even when the 
> respective

Apart from this line now being too long and hence the entire
comment needing re-formatting
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan


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