Re: [Xen-devel] [PATCH V7 3/3] x86/xsaves: ebx may return wrong value using CPUID eax=0xdh, ecx =1

["Jan Beulich" <jbeulich@xxxxxxxx>]

>>> Shuai Ruan <shuai.ruan@xxxxxxxxxxxxxxx> 04/06/16 8:59 AM >>>
>Another question is whether we should add this in pv_cpuid() or not.
>(which we have discussed in the previous thread).
>
>Refer to SDM Volume 1 
>"13.2 ENUMERATION OF CPU SUPPORT FOR XSAVE INSTRUCTIONS AND XSAVE-
>SUPPORTED FEATURES"
>— CPUID function 0DH, sub-function 1.
>...
>"EBX enumerates the size (in bytes) required by the XSAVES instruction
 >for an XSAVE area containing all
 >the state components corresponding to bits currently set in XCR0 |
 >IA32_XSS."
>
>From the descriptions above, EBX only be used when XSAVES is enabled.
>So I think we should not deal with pv_cpuid() here. 

If it's mandated to be XSAVES only - yes. But why are you asking such a 
question?
It was you who proposed the change to pv_cpuid(), and it is you who should be
understanding the specifics of the various pieces of CPUID output related to 
XSAVE
better than me.

Jan


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