From: "Jan Beulich" <JBeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>,
Wei Liu <wei.liu2@citrix.com>
Subject: Re: [PATCH 2/2] x86/HVM: don't calculate XSTATE area sizes in software
Date: Wed, 01 Jun 2016 09:50:10 -0600 [thread overview]
Message-ID: <574F205202000078000F08A5@prv-mh.provo.novell.com> (raw)
In-Reply-To: <574F00D0.20708@citrix.com>
>>> On 01.06.16 at 17:35, <andrew.cooper3@citrix.com> wrote:
> On 01/06/16 16:06, Jan Beulich wrote:
>> @@ -3440,42 +3440,24 @@ void hvm_cpuid(unsigned int input, unsig
>> *eax = *ebx = *ecx = *edx = 0;
>> break;
>> }
>> - /* EBX value of main leaf 0 depends on enabled xsave features */
>> - if ( count == 0 && v->arch.xcr0 )
>> - {
>> - /* reset EBX to default value first */
>> - *ebx = XSTATE_AREA_MIN_SIZE;
>> - for ( sub_leaf = 2; sub_leaf < 63; sub_leaf++ )
>> - {
>> - if ( !(v->arch.xcr0 & (1ULL << sub_leaf)) )
>> - continue;
>> - domain_cpuid(d, input, sub_leaf, &_eax, &_ebx, &_ecx,
>> - &_edx);
>> - if ( (_eax + _ebx) > *ebx )
>> - *ebx = _eax + _ebx;
>> - }
>> - }
>> -
>> - if ( count == 1 )
>> + switch ( count )
>> {
>> + case 1:
>> *eax &= hvm_featureset[FEATURESET_Da1];
>> -
>> - if ( *eax & cpufeat_mask(X86_FEATURE_XSAVES) )
>> + if ( !(*eax & cpufeat_mask(X86_FEATURE_XSAVES)) )
>> {
>> - uint64_t xfeatures = v->arch.xcr0 | v->arch.hvm_vcpu.msr_xss;
>> -
>> - *ebx = XSTATE_AREA_MIN_SIZE;
>> - if ( xfeatures & ~XSTATE_FP_SSE )
>> - for ( sub_leaf = 2; sub_leaf < 63; sub_leaf++ )
>> - if ( xfeatures & (1ULL << sub_leaf) )
>> - {
>> - if ( test_bit(sub_leaf, &xstate_align) )
>> - *ebx = ROUNDUP(*ebx, 64);
>> - *ebx += xstate_sizes[sub_leaf];
>> - }
>> - }
>> - else
>> *ebx = *ecx = *edx = 0;
>> + break;
>> + }
>> + /* fall through */
>> + case 0:
>> + /*
>> + * Always read CPUID.0xD[ECX=0/1].EBX from hardware, rather than
>> + * domain policy. It varies with enabled xstate, and the correct
>> + * xcr0/xss are in context.
>> + */
>> + cpuid_count(input, count, &dummy, ebx, &dummy, &dummy);
>> + break;
>
> It would be helpful for my PKU bugfix if you could avoid collapsing this
> into a fallthough, as the fallthough would need to be undone.
> Otherwise, Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Converting this back is easy to do, but I'll nevertheless wait for
Wei's opinion re 4.7 inclusion, as otherwise I'll eventually need to
rebase on top of yours anyway.
Jan
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next prev parent reply other threads:[~2016-06-01 15:50 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-01 14:57 [PATCH 0/2] x86: xstate CPUID guest output adjustments Jan Beulich
2016-06-01 15:05 ` [PATCH 1/2] x86: flush high xstate CPUID sub-leaves to zero Jan Beulich
2016-06-01 15:30 ` Andrew Cooper
2016-06-01 15:45 ` Wei Liu
2016-06-01 15:06 ` [PATCH 2/2] x86/HVM: don't calculate XSTATE area sizes in software Jan Beulich
2016-06-01 15:35 ` Andrew Cooper
2016-06-01 15:47 ` Wei Liu
2016-06-01 15:50 ` Jan Beulich [this message]
2016-06-01 15:57 ` Wei Liu
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