Re: [Qemu-devel] Re: [PATCH 2/2] introduce -cpu host target

[Filip Navara]

On Wed, Jun 24, 2009 at 11:54 AM, Avi Kivity<address@hidden> 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

Best regards,
Filip Navara