Re: [PATCH v2 5/5] KVM: MMU: retry #PF for softmmu

Gleb Natapov
2010-11-15T09:56:56Z

On Mon, Nov 15, 2010 at 05:55:25PM +0800, Xiao Guangrong wrote:
> On 11/15/2010 05:30 PM, Avi Kivity wrote:
>
> >> Yeah, this 'retry' is unnecessary if the process is killed, but this
> >> case is infrequent, the most case is the process keeps running and try
> >> to access the fault address later.
> >
> > The problem is that if we retry in this case, we install an incorrect spte?
> >
>
> ......
>
> >> can avoid if the page mapping have been fixed.
> >
> > The guest may have changed page directories or other levels.
> >
>
> ......
>
> >> > Or another thread may have mmap()ed something else over the
> >> > same address.
> >>
> >> The mmap virtual address is also visible for other threads since the
> >> threads
> >> have the same page table, so i think this case is the same as above?
> >
> > Again, don't we install the wrong spte in this case?
> >
>
> I think it doesn't corrupts spte since we will walk guest page table again
> and map it to shadow pages when we retry #PF.
But if the page is not mapped by new process we can inject #PF into a
guest.

--
Gleb.