Re: [Xen-devel] [PATCH 1/4] XSAVE/XRSTOR: Fix frozen states

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 31/08/2010 07:56, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>> --- a/xen/arch/x86/i387.c Fri Aug 27 07:10:57 2010 -0400
>> +++ b/xen/arch/x86/i387.c Fri Aug 27 12:31:05 2010 -0400
>> @@ -35,7 +35,10 @@ void save_init_fpu(struct vcpu *v)
>> 
>>     if ( cpu_has_xsave && is_hvm_vcpu(v) )
>>     {
>> +        /* Save all supported feature states */
>> +        set_xcr0(xfeature_mask);
>>         xsave(v);
>> +        set_xcr0(v->arch.hvm_vcpu.xcr0);
>>     }
>>     else if ( cpu_has_fxsr )
>>     {
> 
> Now, I wonder what the (performance) price of this is (and will be with
> larger register sets in the future), and whether the general deferred
> saving scheme can't be made work here too.

Well, quite. Seems the cheap easy fix rather than the right fix, doesn't it.

 -- Keir



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