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

[Zheng, Jiajia]

Hi, Anthony
Anthony Liguori wrote:
> 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. 

Thanks. Will rewrite the patch the way you suggested. 

bests, 
jiajia
> Regards,
> 
> Anthony Liguori
> 
> But then it's not a user visible interface.
> 
>> -Andi