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Date: Wed, 24 Jun 2009 20:46:13 +0300
From: Avi Kivity <avi@redhat.com>
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Subject: Re: [Qemu-devel] Re: [PATCH 2/2] introduce -cpu host target
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To: Filip Navara <filip.navara@gmail.com>
Cc: Andre Przywara <andre.przywara@amd.com>, aliguori@us.ibm.com, qemu-devel@nongnu.org, kvm@vger.kernel.org

On 06/24/2009 08:37 PM, Filip Navara wrote:
> 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.  If a write has some effect the guest
>> depends on, and we're not emulating that effect, the guest will fail.
>>   Similarly if you don't know what a register mean, who knows what returning
>> 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=3&a=3
> http://www.uninformed.org/?v=6&a=1
> http://www.uninformed.org/?v=8&a=5
> http://en.wikipedia.org/wiki/Kernel_Patch_Protection
>
>    

Which unknown msrs are used by kernel patch protection?

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.