On 12/22/2010 01:12 PM, Marcelo Tosatti wrote:
On Wed, Dec 22, 2010 at 01:07:23PM +0200, Avi Kivity wrote:
> On 12/22/2010 01:01 PM, Marcelo Tosatti wrote:
> >If a pagetable contains a writeable large spte, all of its sptes will be
>
> non-writeable
>
> >write protected, including non-leaf ones, leading to endless pagefaults.
> >
> >Do not write protect pages above PT_PAGE_TABLE_LEVEL, as the spte fault
> >paths assume non-leaf sptes are writable.
> >
> >Signed-off-by: Marcelo Tosatti<[email protected]>
> >
> >diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> >index c3853d5..c716ff8 100644
> >--- a/arch/x86/kvm/mmu.c
> >+++ b/arch/x86/kvm/mmu.c
> >@@ -3442,6 +3442,9 @@ void kvm_mmu_slot_remove_write_access(struct kvm
*kvm, int slot)
> > if (!test_bit(slot, sp->slot_bitmap))
> > continue;
> >
> >+ if (sp->role.level != PT_PAGE_TABLE_LEVEL)
> >+ continue;
> >+
> > pt = sp->spt;
> > for (i = 0; i< PT64_ENT_PER_PAGE; ++i)
> > /* avoid RMW */
>
> But what about large leaf sptes? Don't we want to write protect, or
> perhaps drop them?
>
> I think write-protecting leaf sptes and ignoring nonleaf sptes should work.
When dirty logging is enabled large sptes are nuked and creation of new
ones is not allowed. So i don't see the need?
Where does this nuking happen?
All I see is the call to kvm_mmu_slot_remove_write_access().
--
error compiling committee.c: too many arguments to function
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