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From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: "Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	x86@kernel.org, "Peter Zijlstra" <peterz@infradead.org>,
	"Arnaldo Carvalho de Melo" <acme@kernel.org>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"Tony Luck" <tony.luck@intel.com>,
	"Tony W Wang-oc" <TonyWWang-oc@zhaoxin.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Alexander Shishkin" <alexander.shishkin@linux.intel.com>,
	"Jiri Olsa" <jolsa@redhat.com>,
	"Namhyung Kim" <namhyung@kernel.org>,
	"Vitaly Kuznetsov" <vkuznets@redhat.com>,
	"Wanpeng Li" <wanpengli@tencent.com>,
	"Jim Mattson" <jmattson@google.com>,
	"Joerg Roedel" <joro@8bytes.org>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	linux-edac@vger.kernel.org, "Borislav Petkov" <bp@suse.de>,
	"Jarkko Sakkinen" <jarkko.sakkinen@linux.intel.com>
Subject: Re: [PATCH 10/16] x86/cpu: Detect VMX features on Intel, Centaur and Zhaoxin CPUs
Date: Tue, 8 Oct 2019 08:55:50 +0200	[thread overview]
Message-ID: <8b44345d-7bc0-b8f2-0ee4-3e7f3c8bd994@redhat.com> (raw)
In-Reply-To: <20191007195422.GF18016@linux.intel.com>

On 07/10/19 21:54, Sean Christopherson wrote:
>> For QEMU, we're defining a feature as supported if a feature can be
>> turned both on and off.  Since msr_low and msr_high can be defined
>> respectively as must-be-one and can-be-one, the features become
>> "msr_high & ~msr_low".
> 
> That makes sense for Qemu, but I don't think it's appropriate for this
> type of reporting.  E.g. if EPT and Unrestricted Guest are must-be-one on
> a hypothetical (virtual) CPU, it'd be odd to not list them as a supported
> feature.
> 
> For actual hardware (well, Intel hardware), as proposed it's a moot point.
> The only features that are must-be-one (even without "true" MSRs) and are
> documented in the SDM are CR3_LOAD_EXITING, CR3_STORE_EXITING,
> SAVE_DEBUG_CONTROLS, and LOAD_DEBUG_CONTROLS, none of which are reported
> in /proc/cpuinfo.
> 
>> Also, shouldn't this use the "true" feature availability MSRs if available?
> 
> Only if incorporating the "& ~msr_low" can-be-one logic.  If a feature is
> considered supported if it must-be-one or can-be-one then the true MSR and
> vanilla MSR will yield the same feature set.

Ok, that all makes sense.

Paolo

  reply	other threads:[~2019-10-08  6:55 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-04 21:55 [PATCH 00/16] x86/cpu: Clean up handling of VMX features Sean Christopherson
2019-10-04 21:56 ` [PATCH 01/16] x86/intel: Initialize IA32_FEATURE_CONTROL MSR at boot Sean Christopherson
2019-10-07 17:05   ` Paolo Bonzini
2019-10-07 17:10     ` Sean Christopherson
2019-10-04 21:56 ` [PATCH 02/16] x86/mce: WARN once if IA32_FEATURE_CONTROL MSR is left unlocked Sean Christopherson
2019-10-04 21:56 ` [PATCH 03/16] x86/centaur: Use common IA32_FEATURE_CONTROL MSR initialization Sean Christopherson
2019-10-04 21:56 ` [PATCH 04/16] x86/zhaoxin: " Sean Christopherson
2019-10-04 21:56 ` [PATCH 05/16] KVM: VMX: Drop initialization of IA32_FEATURE_CONTROL MSR Sean Christopherson
2019-10-04 23:24   ` Jim Mattson
2019-10-04 21:56 ` [PATCH 06/16] x86/cpu: Clear VMX feature flag if VMX is not fully enabled Sean Christopherson
2019-10-04 21:56 ` [PATCH 07/16] KVM: VMX: Use VMX feature flag to query BIOS enabling Sean Christopherson
2019-10-04 23:26   ` Jim Mattson
2019-10-04 21:56 ` [PATCH 08/16] KVM: VMX: Check for full VMX support when verifying CPU compatibility Sean Christopherson
2019-10-04 23:35   ` Jim Mattson
2019-10-04 21:56 ` [PATCH 09/16] x86/vmx: Introduce VMX_FEATURES_* Sean Christopherson
2019-10-07 17:08   ` Paolo Bonzini
2019-10-07 17:13     ` Sean Christopherson
2019-10-04 21:56 ` [PATCH 10/16] x86/cpu: Detect VMX features on Intel, Centaur and Zhaoxin CPUs Sean Christopherson
2019-10-07 17:11   ` Paolo Bonzini
2019-10-07 19:54     ` Sean Christopherson
2019-10-08  6:55       ` Paolo Bonzini [this message]
2019-10-04 21:56 ` [PATCH 11/16] x86/cpu: Print VMX features as separate line item in /proc/cpuinfo Sean Christopherson
2019-10-07 17:12   ` Paolo Bonzini
2019-10-07 19:56     ` Sean Christopherson
2019-10-08  6:57       ` Paolo Bonzini
2019-10-08 16:53         ` Jim Mattson
2019-10-09 19:16         ` Sean Christopherson
2019-10-09 21:13           ` Paolo Bonzini
2019-10-04 21:56 ` [PATCH 12/16] x86/cpufeatures: Drop synthetic VMX feature flags Sean Christopherson
2019-10-04 21:56 ` [PATCH 13/16] KVM: VMX: Use VMX_FEATURE_* flags to define VMCS control bits Sean Christopherson
2019-10-04 21:56 ` [PATCH 14/16] x86/cpufeatures: Clean up synthetic virtualization flags Sean Christopherson
2019-10-04 21:56 ` [PATCH 15/16] perf/x86: Provide stubs of KVM helpers for non-Intel CPUs Sean Christopherson
2019-10-04 21:56 ` [PATCH 16/16] KVM: VMX: Allow KVM_INTEL when building for Centaur and/or Zhaoxin CPUs Sean Christopherson
2019-10-10  7:34 [PATCH 10/16] x86/cpu: Detect VMX features on Intel, Centaur and " Tony W Wang-oc

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