Re: [PATCH] x86/CPUID: surface suitable value in EBX of XSTATE subleaf 1

[Andrew Cooper <Andrew.Cooper3@citrix.com>]

On 23/08/2022 13:01, Jan Beulich wrote:
> On 23.08.2022 12:48, Andrew Cooper wrote:
>> On 23/08/2022 10:27, Jan Beulich wrote:
>>> On 23.08.2022 10:59, Andrew Cooper wrote:
>>>> On 23/08/2022 07:42, Jan Beulich wrote:
>>>>> +++ b/xen/arch/x86/cpuid.c
>>>>> @@ -1142,7 +1142,7 @@ void guest_cpuid(const struct vcpu *v, u
>>>>>          switch ( subleaf )
>>>>>          {
>>>>>          case 1:
>>>>> -            if ( p->xstate.xsaves )
>>>>> +            if ( p->xstate.xsavec || p->xstate.xsaves )
>>>> If we're doing this, then it wants to be xsavec only, with the comment
>>>> being extended to explain why.
>>> Why would that be? Both insns use compacted format, and neither is
>>> dependent upon the other in terms of being supported. IOW XSAVES alone
>>> and XSAVEC alone enabled for a domain should still lead through this
>>> path.
>> Hmm.  Because my fixes to compaction handling haven't been committed
>> yet, and in particular one the one which makes XSAVES strictly depend on
>> XSAVEC.
>>
>> In which case this hunk is correct for Xen as it currently is, and will
>> be need to be adjusted when I rebase the compaction series.
> May I translate this to an Ack then? Iirc there were no other change
> requests.

I was hoping that Marek would have time to test it too, seeing as he
reported the bug first.  But seeing as he's busy...

Acked-by: Andrew Cooper <andrew.cooper3@citrix.com> (with the typo in
the commit message fixed.)

~Andrew