Re: [PATCH v3 0/4] Fix accessed bit tracking

[Marcelo Tosatti <mtosatti@redhat.com>]

On Mon, Jul 05, 2010 at 03:39:09PM +0300, Avi Kivity wrote:
> The kvm mmu synchronizes shadow ptes using the mmu lock, however the cpu
> will happily ignore the lock when setting the accessed bit.  This can cause
> the accessed bit to be lost.  Luckily this only results in incorrect page
> selection for swap.
> 
> This patchset fixes the problem by atomically updating the spte when
> needed while taking care of the accessed bit.
> 
> v3: fix i386 pte exchange code in patch 3
>     add missing __set_spte() to drop_spte() in patch 2
> 
> v2: fix incorrect code transformations in first patch
> 
> Avi Kivity (4):
>   KVM: MMU: Introduce drop_spte()
>   KVM: MMU: Move accessed/dirty bit checks from rmap_remove() to
>     drop_spte()
>   KVM: MMU: Atomically check for accessed bit when dropping an spte
>   KVM: MMU: Don't drop accessed bit while updating an spte
> 
>  arch/x86/kvm/mmu.c         |   88 +++++++++++++++++++++++++++++++------------
>  arch/x86/kvm/paging_tmpl.h |   13 +++---
>  2 files changed, 69 insertions(+), 32 deletions(-)

Looks good to me.