From: Paolo Bonzini <pbonzini@redhat.com>
To: David Woodhouse <dwmw2@infradead.org>, Jim Mattson <jmattson@google.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
"kvm list" <kvm@vger.kernel.org>,
"KarimAllah Ahmed" <karahmed@amazon.de>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
stable@vger.kernel.org
Subject: Re: [PATCH 7/9] KVM/VMX: Emulate MSR_IA32_ARCH_CAPABILITIES
Date: Mon, 19 Feb 2018 15:07:11 +0100 [thread overview]
Message-ID: <6ef598e6-de89-abdb-f157-dc12bb24ef9d@redhat.com> (raw)
In-Reply-To: <1519047329.7876.64.camel@infradead.org>
On 19/02/2018 14:35, David Woodhouse wrote:
> On Mon, 2018-02-19 at 14:10 +0100, Paolo Bonzini wrote:
>>> Hardware seems like a reasonable place to get the default value (cf.
>>> the VMX capability MSRs).
>>
>> There are some differences:
>>
>> - a zero value for ARCH_CAPABILITIES should be safe, while a zero value
>> for VMX capabilities doesn't really make sense. On the contrary, a
>> nonzero value for ARCH_CAPABILITIES is not safe across live migration.
>
> Any VMM which is going to support live migration surely needs to pay at
> least a small amount of attention to the features it exposes? Exposing
> the ARCH_CAPABILITIES CPUID bit without actually looking at the
> contents of the associated MSR which that bit advertises would be... a
> little strange, would it not?
I think what we should do is simply backport Tom Lendacky's series to
4.14 and 4.9 ASAP, and add ARCH_CAPABILITIES support there. Then the
question of the default becomes moot, more or less.
Paolo
> I don't see why we care so much about the *default* value, in that
> context.
next prev parent reply other threads:[~2018-02-19 14:07 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-06 17:29 [STABLE 4.9.y PATCH 0/9] Backport of KVM Speculation Control support David Woodhouse
2018-02-06 17:29 ` [PATCH 1/9] KVM: nVMX: vmx_complete_nested_posted_interrupt() can't fail David Woodhouse
2018-02-06 17:29 ` [PATCH 2/9] KVM: nVMX: mark vmcs12 pages dirty on L2 exit David Woodhouse
2018-02-06 17:29 ` [PATCH 3/9] KVM: nVMX: Eliminate vmcs02 pool David Woodhouse
2018-02-06 17:29 ` [PATCH 4/9] KVM: VMX: introduce alloc_loaded_vmcs David Woodhouse
2018-02-06 17:29 ` [PATCH 5/9] KVM: VMX: make MSR bitmaps per-VCPU David Woodhouse
2018-02-06 17:29 ` [PATCH 6/9] KVM/x86: Add IBPB support David Woodhouse
2018-02-06 17:29 ` [PATCH 7/9] KVM/VMX: Emulate MSR_IA32_ARCH_CAPABILITIES David Woodhouse
2018-02-16 14:18 ` Paolo Bonzini
2018-02-16 16:29 ` Jim Mattson
2018-02-16 16:33 ` David Woodhouse
2018-02-19 13:10 ` Paolo Bonzini
2018-02-19 13:35 ` David Woodhouse
2018-02-19 14:07 ` Paolo Bonzini [this message]
2018-02-06 17:29 ` [PATCH 8/9] KVM/VMX: Allow direct access to MSR_IA32_SPEC_CTRL David Woodhouse
2018-02-16 4:02 ` Jim Mattson
2018-02-16 4:16 ` Jim Mattson
2018-02-06 17:29 ` [PATCH 9/9] KVM/SVM: " David Woodhouse
2018-02-06 18:01 ` [STABLE 4.9.y PATCH 0/9] Backport of KVM Speculation Control support Paolo Bonzini
2018-02-06 21:05 ` Woodhouse, David
2018-02-08 2:49 ` Greg KH
2018-02-08 17:14 ` Greg KH
2018-02-08 17:42 ` Paolo Bonzini
2018-02-08 17:57 ` Greg KH
2018-02-09 7:58 ` Greg KH
2018-02-15 10:15 ` Thomas Voegtle
2018-02-15 10:23 ` Greg KH
2018-02-15 10:49 ` Thomas Voegtle
2018-02-15 13:57 ` Greg KH
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