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Date: Wed, 24 Jun 2009 19:37:23 +0200
Message-ID: <5b31733c0906241037t54706611w19eeb2f27f8e63f3@mail.gmail.com>
Subject: Re: [Qemu-devel] Re: [PATCH 2/2] introduce -cpu host target
From: Filip Navara <filip.navara@gmail.com>
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To: Avi Kivity <avi@redhat.com>
Cc: Andre Przywara <andre.przywara@amd.com>, aliguori@us.ibm.com, qemu-devel@nongnu.org, kvm@vger.kernel.org

On Wed, Jun 24, 2009 at 11:54 AM, Avi Kivity<avi@redhat.com> wrote:
> On 06/23/2009 12:47 AM, Andre Przywara wrote:
>>
>> Should we ignore unhandled MSRs like QEMU or Xen do?
>>
>
> Ignoring unhandled msrs is dangerous. =A0If a write has some effect the g=
uest
> depends on, and we're not emulating that effect, the guest will fail.
> =A0Similarly if you don't know what a register mean, who knows what retur=
ning
> zero for a read will do.

It is definitely a bad idea to ignore unknown MSRs. Kernel patch
protection scheme used by certain operating system depend on them to
work properly and it's pretty hard to debug when you don't know what
failed (the MSR read in this case).

http://www.uninformed.org/?v=3D3&a=3D3
http://www.uninformed.org/?v=3D6&a=3D1
http://www.uninformed.org/?v=3D8&a=3D5
http://en.wikipedia.org/wiki/Kernel_Patch_Protection

Best regards,
Filip Navara