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

[Avi Kivity]

On 04/27/2010 04:28 PM, Joerg Roedel wrote:
> > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > > index d9dfc8c..8426870 100644
> > > --- a/arch/x86/include/asm/kvm_host.h
> > > +++ b/arch/x86/include/asm/kvm_host.h
> > > @@ -298,6 +298,9 @@ struct kvm_vcpu_arch {
> > >   	/* Used for two dimensional paging emulation */
> > >   	struct kvm_mmu nested_mmu;
> > >
> > > +	unsigned long fault_address;
> > >        
> > Probably a problem on i386.  How does npt handle faults when the
> > guest is using pae paging and the host (in our case the guest...)
> > isn't?  I see it uses exit_info_2 for the address, which is a u64.
> >      
> This shouldn't be an issue. If we run on 32bit host with nested paging
> the guest can't have more than 4gb of addressable memory because of the
> page table limitations (nested page table is always in host format).
>    

But the nested guest can use pae paging and generate a #NPF with 
exit_info_2 > 4GB.  So we need to keep the full fault address; if we 
truncate, the guest might actually resolve the fault and let the nested 
guest continue.

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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/