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Subject: Re: [PATCH 7/9] KVM/VMX: Emulate MSR_IA32_ARCH_CAPABILITIES
To: Jim Mattson <jmattson@google.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?=
 <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
References: <1517938181-15317-1-git-send-email-dwmw@amazon.co.uk>
 <1517938181-15317-8-git-send-email-dwmw@amazon.co.uk>
 <4be4e462-61be-53a9-b0e1-3508466d1645@redhat.com>
 <CALMp9eQQ-94g=fNanvwpr6b2pmH87RPGr6s9gOv43dUDABFuhw@mail.gmail.com>
From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <a4693ca3-face-e1f5-b619-74fc59870ce9@redhat.com>
Date: Mon, 19 Feb 2018 14:10:11 +0100
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On 16/02/2018 17:29, Jim Mattson wrote:
> On Fri, Feb 16, 2018 at 6:18 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
>> Uhm, taking contents from the hardware is wrong (guess why---live
>> migration).  I'll send a revert of those two lines.
> 
> 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.

- VMX doesn't support live migration; before adding that support we will
probably have Tom's patches to retrieve MSR capabilities.

Thanks,

Paolo

> Should these two lines just be moved to
> vmx_create_cpu?
>