Re: [PATCH 16/22] KVM: MMU: Track page fault data in struct vcpu

[Avi Kivity]

On 05/04/2010 03:00 PM, Roedel, Joerg wrote:
> On Tue, May 04, 2010 at 05:50:50AM -0400, Avi Kivity wrote:
>    
> > On 05/04/2010 12:45 PM, Avi Kivity wrote:
> >      
> > > Just a silly bug.  kvm_pdptr_read() can cause a guest memory read on
> > > svm, in this case with the mmu lock taken.  I'll post something to fix
> > > it.
> > >        
> > I guess this was not reported because most svm machines have npt, and
> > this requires npt=0 to trigger.  Nonpae paging disables npt, so you were
> > hit.  Interestingly, nsvm makes it more likely to appear, since npt on
> > i386+pae will need the pdptrs.
> >      
> Hmm, actually it happened on 32 bit with npt enabled. I think this
> can trigger when mmu_alloc_roots is called for an pae guest because it
> accidentially tries read the root_gfn from the guest before it figures
> out that it runs with tdp and omits the gfn read from the guest.
>    

Yes.  I had a patchset which moved the 'direct' calculation before, and 
skipped root_gfn if it was direct, but it was broken.  If you like I can 
resurrect it, but it may interfere with your work.

--
error compiling committee.c: too many arguments to function

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