Re: [Qemu-devel] [Patch] Support translating Guest physical address to Host virtual address.

[Anthony Liguori <aliguori@linux.vnet.ibm.com>]

On 02/03/2010 09:49 AM, Kleen, Andi wrote:
>    
>> Yeah, but if we put a feature in qemu, we need to be able to
>> support it
>> for anyone who wants to use it.
>>      
> It's useful for anyone who wants to use it for testing purposes.
> And it's useful to make sure the qemu/kernel/kvm machine check
> injection code works.
>
>    
>> Adding something for a very particular test suite that won't work in
>> normal circumstances is just asking for trouble IMHO.
>>      
> RAS features generally need associated testing/injection hooks,
> otherwise they don't get tested regularly enough and bitrot.
>
>    
>> I still don't really understand all the pieces that are
>> involved here.
>> Why do we need a guest physical address?  Are we testing
>> reflecting MCEs
>>      
> >from the host into a guest?  Since that functionality isn't in qemu
>    
>> aren't we putting the cart before the horse here?
>>      
> qemu has support for triggering MCEs on the monitor.
>
> Also the KVM code base has support for forwarding the MCEs automatically.
>    

KVM has all of the information you need (guest physical -> host physical 
mapping).  It can also pin the mapping making it much safer to interface 
at that level.  You should probably add an ioctl interface to KVM to get 
a host physical from a given guest physical and then use that to do the 
MCE injection.  You would need to write a little helper tool and you 
would need a way to get an fd for an existing guest.

Regards,

Anthony Liguori

But then it's not a user visible interface.

> -Andi
>