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From: Paolo Bonzini <pbonzini@redhat.com>
To: Jim Mattson <jmattson@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	kvm list <kvm@vger.kernel.org>,
	Sean Christopherson <sean.j.christopherson@intel.com>
Subject: Re: [PATCH 4/5] KVM: vmx: implement MSR_IA32_TSX_CTRL disable RTM functionality
Date: Thu, 5 Dec 2019 11:16:16 +0100	[thread overview]
Message-ID: <d0653777-55c6-ebb9-7be7-5bdd259b66fa@redhat.com> (raw)
In-Reply-To: <CALMp9eTKMzg2pNEZxhqAejAquFg8NxKRrBzzNUKRY78JLGjS5A@mail.gmail.com>

On 05/12/19 00:49, Jim Mattson wrote:
>>         if (!boot_cpu_has(X86_FEATURE_RTM))
>> -               data &= ~ARCH_CAP_TAA_NO;
>> +               data &= ~(ARCH_CAP_TAA_NO | ARCH_CAP_TSX_CTRL_MSR);
>>         else if (!boot_cpu_has_bug(X86_BUG_TAA))
>>                 data |= ARCH_CAP_TAA_NO;
>> -       else if (data & ARCH_CAP_TSX_CTRL_MSR)
>> -               data &= ~ARCH_CAP_MDS_NO;
>>
>> -       /* KVM does not emulate MSR_IA32_TSX_CTRL.  */
>> -       data &= ~ARCH_CAP_TSX_CTRL_MSR;
> Shouldn't kvm be masking off any bits that it doesn't know about here?
> Who knows what future features we may claim to support?

Good question, in the past the ARCH_CAPABILITIES were just "we don't
have this bug" so it made sense to pass everything through.  Now we have
TSX_CTRL that is of a different kind and arguably should have been a
CPUID bit, so we should indeed mask unknown capabilties.

Paolo


  reply	other threads:[~2019-12-05 10:16 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-18 18:17 [PATCH 0/5] KVM: vmx: implement MSR_IA32_TSX_CTRL for guests Paolo Bonzini
2019-11-18 18:17 ` [PATCH 1/5] KVM: x86: fix presentation of TSX feature in ARCH_CAPABILITIES Paolo Bonzini
2019-11-18 19:39   ` Jim Mattson
2019-11-18 20:48   ` Jim Mattson
2019-11-22 20:15   ` Sean Christopherson
2019-11-18 18:17 ` [PATCH 2/5] KVM: x86: do not modify masked bits of shared MSRs Paolo Bonzini
2019-11-19 19:00   ` Jim Mattson
2019-11-18 18:17 ` [PATCH 3/5] KVM: x86: implement MSR_IA32_TSX_CTRL effect on CPUID Paolo Bonzini
2019-11-19 20:02   ` Jim Mattson
2019-11-18 18:17 ` [PATCH 4/5] KVM: vmx: implement MSR_IA32_TSX_CTRL disable RTM functionality Paolo Bonzini
2019-11-19 21:06   ` Jim Mattson
2019-11-20 12:21     ` Paolo Bonzini
2019-12-04 23:49   ` Jim Mattson
2019-12-05 10:16     ` Paolo Bonzini [this message]
2019-11-18 18:17 ` [PATCH 5/5] KVM: vmx: use MSR_IA32_TSX_CTRL to hard-disable TSX on guest that lack it Paolo Bonzini
2019-11-21  2:22   ` Eduardo Habkost
2019-11-21  9:05     ` Paolo Bonzini

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