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

[Avi Kivity]

On 06/24/2009 08:37 PM, Filip Navara wrote:
> 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
>
>    

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.