Re: [Xen-devel] [PATCHv3 2/3] x86/fpu: Add a per-domain field to set the width of FIP/FDP

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 25/02/16 11:24, Jan Beulich wrote:
>>>> On 25.02.16 at 11:58, <david.vrabel@xxxxxxxxxx> wrote:
>> @@ -261,7 +261,15 @@ void xsave(struct vcpu *v, uint64_t mask)
>>                           "=m" (*ptr), \
>>                           "a" (lmask), "d" (hmask), "D" (ptr))
>>  
>> -    if ( word_size <= 0 || !is_pv_32bit_vcpu(v) )
>> +    if ( fip_width == 8 )
>> +    {
>> +        XSAVE("0x48,");
>> +    }
>> +    else if ( fip_width == 4 )
>> +    {
>> +        XSAVE("");
>> +    }
>> +    else
> 
> Both conditions would now better also check mask & XSTATE_FP,
> since going these routes (and namely bypassing the FIP check, as
> was done before) is fine when FP state is not being saved.

Is this what you mean?

--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -261,7 +261,7 @@ void xsave(struct vcpu *v, uint64_t mask)
                          "=m" (*ptr), \
                          "a" (lmask), "d" (hmask), "D" (ptr))

-    if ( fip_width == 8 )
+    if ( fip_width == 8 || !(mask & XSTATE_FP) )
     {
         XSAVE("0x48,");
     }

David

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