From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: Xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH v3 20/28] x86/domctl: Update PV domain cpumasks when setting cpuid policy
Date: Tue, 22 Mar 2016 16:37:09 +0000 [thread overview]
Message-ID: <56F174B5.9050707@citrix.com> (raw)
In-Reply-To: <56F0383A02000078000DEFA5@prv-mh.provo.novell.com>
On 21/03/16 17:06, Jan Beulich wrote:
>>>> On 15.03.16 at 16:35, <andrew.cooper3@citrix.com> wrote:
>> @@ -87,6 +88,129 @@ static void update_domain_cpuid_info(struct domain *d,
>> d->arch.x86_model = (ctl->eax >> 4) & 0xf;
>> if ( d->arch.x86 >= 0x6 )
>> d->arch.x86_model |= (ctl->eax >> 12) & 0xf0;
>> +
>> + if ( is_pv_domain(d) && ((levelling_caps & LCAP_1cd) == LCAP_1cd) )
>> + {
>> + uint64_t mask = cpuidmask_defaults._1cd;
>> + uint32_t ecx = ctl->ecx & pv_featureset[FEATURESET_1c];
>> + uint32_t edx = ctl->edx & pv_featureset[FEATURESET_1d];
>> +
>> + /*
>> + * Must expose hosts HTT value so a guest using native CPU can
> DYM "native CPUID" here?
Yes.
>
>> + * correctly interpret other leaves which cannot be masked.
>> + */
>> + edx &= ~cpufeat_mask(X86_FEATURE_HTT);
>> + if ( cpu_has_htt )
>> + edx |= cpufeat_mask(X86_FEATURE_HTT);
>> +
>> + switch ( boot_cpu_data.x86_vendor )
>> + {
>> + case X86_VENDOR_INTEL:
>> + mask &= ((uint64_t)edx << 32) | ecx;
>> + break;
>> +
>> + case X86_VENDOR_AMD:
>> + mask &= ((uint64_t)ecx << 32) | edx;
>> +
>> + /* Fast-forward bits - Must be set. */
>> + if (ecx & cpufeat_mask(X86_FEATURE_XSAVE))
> Missing blanks inside parens. Also I think the comment should be
> expanded to include the fact that the need to do this here but
> not in the Intel case was empirically(?) determined
It was empirically determined that AMD did have to behave like this.
> - just in case
> something isn't quite right with this on some future hardware,
> and readers (possibly including ourselves) wonder.
Intel and AMD masking MSRs are fundamentally different, and function
differently.
Intel MSRs are documented strictly an & mask, and experimentally, are
applied before OSXSAVE/APIC are fast-forwarded from hardware.
AMD MSRs are documented strictly as an override, with a caution to avoid
setting bits which aren't actually supported in the hardware, and
experimentally need the fast-forward bits set if fast-forwarding is to
occur.
I suppose I could split this up and move this logic into
cpu/{amd,intel}.c as appropriate, and call a vendor specific function to
appropriately translate a guest cpuid value into a mask value. However,
a lot of common logic would end up needing to be duplicated.
>
>> + case X86_VENDOR_AMD:
>> + /*
>> + * Must expose hosts CMP_LEGACY value so a guest using native
>> + * CPU can correctly interpret other leaves which cannot be
> CPUID again?
Yes
>
>> + * masked.
>> + */
>> + ecx &= ~cpufeat_mask(X86_FEATURE_CMP_LEGACY);
>> + if ( cpu_has_cmp_legacy )
>> + ecx |= cpufeat_mask(X86_FEATURE_CMP_LEGACY);
>> +
>> + mask &= ((uint64_t)ecx << 32) | edx;
>> +
>> + /* Fast-forward bits - Must be set. */
>> + ecx = 0;
>> + edx = cpufeat_mask(X86_FEATURE_APIC);
>> +
>> + mask |= ((uint64_t)ecx << 32) | edx;
> This certainly looks strange (as in more complicated than it needs to
> be) - why not just mask |= cpufeat_mask(X86_FEATURE_APIC)?
Copy and paste from the leaf 1 case. I specifically wanted to avoid
directly manipulating the mask value, as it is already confusing enough
which way ecx and edx are.
~Andrew
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next prev parent reply other threads:[~2016-03-22 16:37 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-15 15:34 [PATCH RFC v3 00/28] x86: Improvements to cpuid handling for guests Andrew Cooper
2016-03-15 15:34 ` [PATCH v3 01/28] xen/x86: Drop unused and non-useful feature definitions Andrew Cooper
2016-03-16 7:53 ` Konrad Rzeszutek Wilk
2016-03-16 9:49 ` Andrew Cooper
2016-03-22 14:06 ` Doug Goldstein
2016-03-22 14:38 ` Jan Beulich
2016-03-15 15:34 ` [PATCH v3 02/28] xen/x86: Rename features to be closer to the vendor definitions Andrew Cooper
2016-03-16 8:01 ` Konrad Rzeszutek Wilk
2016-03-17 19:46 ` Andrew Cooper
2016-03-15 15:34 ` [PATCH v3 03/28] xen/public: Export cpu featureset information in the public API Andrew Cooper
2016-03-16 8:32 ` Konrad Rzeszutek Wilk
2016-03-22 10:39 ` Andrew Cooper
2016-03-18 15:52 ` Jan Beulich
2016-03-15 15:35 ` [PATCH v3 04/28] xen/x86: Script to automatically process featureset information Andrew Cooper
2016-03-16 8:41 ` Konrad Rzeszutek Wilk
2016-03-15 15:35 ` [PATCH v3 05/28] xen/x86: Collect more cpuid feature leaves Andrew Cooper
2016-03-16 8:50 ` Konrad Rzeszutek Wilk
2016-03-15 15:35 ` [PATCH v3 06/28] xen/x86: Mask out unknown features from Xen's capabilities Andrew Cooper
2016-03-16 18:01 ` Konrad Rzeszutek Wilk
2016-03-15 15:35 ` [PATCH v3 07/28] xen/x86: Annotate special features Andrew Cooper
2016-03-16 18:04 ` Konrad Rzeszutek Wilk
2016-03-18 16:29 ` Jan Beulich
2016-03-15 15:35 ` [PATCH v3 08/28] xen/x86: Annotate VM applicability in featureset Andrew Cooper
2016-03-16 18:15 ` Konrad Rzeszutek Wilk
2016-03-18 16:57 ` Jan Beulich
2016-03-18 18:56 ` Andrew Cooper
2016-03-21 11:53 ` Jan Beulich
2016-03-21 13:39 ` Andrew Cooper
2016-03-15 15:35 ` [PATCH v3 09/28] xen/x86: Calculate maximum host and guest featuresets Andrew Cooper
2016-03-16 18:24 ` Konrad Rzeszutek Wilk
2016-03-18 17:09 ` Jan Beulich
2016-03-22 11:23 ` Andrew Cooper
2016-03-22 12:39 ` Jan Beulich
2016-03-22 14:37 ` Andrew Cooper
2016-03-22 14:52 ` Jan Beulich
2016-03-22 15:01 ` Andrew Cooper
2016-03-22 16:10 ` Jan Beulich
2016-03-15 15:35 ` [PATCH v3 10/28] xen/x86: Generate deep dependencies of features Andrew Cooper
2016-03-17 19:45 ` Konrad Rzeszutek Wilk
2016-03-17 20:14 ` Andrew Cooper
2016-03-17 20:32 ` Konrad Rzeszutek Wilk
2016-03-21 15:41 ` Jan Beulich
2016-03-15 15:35 ` [PATCH v3 11/28] xen/x86: Clear dependent features when clearing a cpu cap Andrew Cooper
2016-03-17 19:51 ` Konrad Rzeszutek Wilk
2016-03-17 19:56 ` Andrew Cooper
2016-03-28 15:02 ` Konrad Rzeszutek Wilk
2016-03-21 15:45 ` Jan Beulich
2016-03-15 15:35 ` [PATCH v3 12/28] xen/x86: Improve disabling of features which have dependencies Andrew Cooper
2016-03-15 15:35 ` [PATCH v3 13/28] xen/x86: Improvements to in-hypervisor cpuid sanity checks Andrew Cooper
2016-03-21 16:11 ` Jan Beulich
2016-03-22 15:30 ` Andrew Cooper
2016-03-15 15:35 ` [PATCH v3 14/28] x86/cpu: Move set_cpumask() calls into c_early_init() Andrew Cooper
2016-03-21 16:16 ` Jan Beulich
2016-03-15 15:35 ` [PATCH v3 15/28] x86/cpu: Sysctl and common infrastructure for levelling context switching Andrew Cooper
2016-03-15 17:35 ` Joao Martins
2016-03-15 19:29 ` Andrew Cooper
2016-03-15 19:34 ` Joao Martins
2016-03-21 16:23 ` Jan Beulich
2016-03-22 15:57 ` Andrew Cooper
2016-03-22 16:16 ` Jan Beulich
2016-03-15 15:35 ` [PATCH v3 16/28] x86/cpu: Rework AMD masking MSR setup Andrew Cooper
2016-03-21 16:51 ` Jan Beulich
2016-03-21 16:55 ` Andrew Cooper
2016-03-15 15:35 ` [PATCH v3 17/28] x86/cpu: Rework Intel masking/faulting setup Andrew Cooper
2016-03-21 16:44 ` Jan Beulich
2016-03-15 15:35 ` [PATCH v3 18/28] x86/cpu: Context switch cpuid masks and faulting state in context_switch() Andrew Cooper
2016-03-15 15:35 ` [PATCH v3 19/28] x86/pv: Provide custom cpumasks for PV domains Andrew Cooper
2016-03-21 16:53 ` Jan Beulich
2016-03-15 15:35 ` [PATCH v3 20/28] x86/domctl: Update PV domain cpumasks when setting cpuid policy Andrew Cooper
2016-03-21 17:06 ` Jan Beulich
2016-03-22 16:37 ` Andrew Cooper [this message]
2016-03-22 16:51 ` Jan Beulich
2016-03-15 15:35 ` [PATCH v3 21/28] xen+tools: Export maximum host and guest cpu featuresets via SYSCTL Andrew Cooper
2016-03-16 18:23 ` Wei Liu
2016-03-16 20:38 ` David Scott
2016-03-22 8:43 ` Jan Beulich
2016-03-22 20:39 ` Andrew Cooper
2016-03-15 15:35 ` [PATCH v3 22/28] tools/libxc: Modify bitmap operations to take void pointers Andrew Cooper
2016-03-16 15:24 ` Andrew Cooper
2016-03-17 12:17 ` Wei Liu
2016-03-15 15:35 ` [PATCH v3 23/28] tools/libxc: Use public/featureset.h for cpuid policy generation Andrew Cooper
2016-03-15 15:35 ` [PATCH v3 24/28] tools/libxc: Expose the automatically generated cpu featuremask information Andrew Cooper
2016-03-15 15:35 ` [PATCH v3 25/28] tools: Utility for dealing with featuresets Andrew Cooper
2016-03-16 18:23 ` Wei Liu
2016-03-15 15:35 ` [PATCH v3 26/28] tools/libxc: Wire a featureset through to cpuid policy logic Andrew Cooper
2016-03-15 15:35 ` [PATCH v3 27/28] tools/libxc: Use featuresets rather than guesswork Andrew Cooper
2016-03-15 15:35 ` [PATCH v3 28/28] tools/libxc: Calculate xstate cpuid leaf from guest information Andrew Cooper
2016-03-16 18:23 ` Wei Liu
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