Re: [PATCH 0/4] Unlocked TLB flush

[Marcelo Tosatti <mtosatti@redhat.com>]

On Mon, May 07, 2012 at 10:25:34PM -0300, Marcelo Tosatti wrote:
> On Thu, May 03, 2012 at 02:22:58PM +0300, Avi Kivity wrote:
> > This patchset implements unlocked TLB flushing for KVM.  An operation that
> > generates stale TLB entries can mark the TLB as dirty instead of flushing
> > immediately, and then flush after releasing mmu_lock but before returning
> > to the guest or the caller.  A few call sites are converted too.
> > 
> > Note not all call sites are easily convertible; as an example, sync_page()
> > must flush before reading the guest page table.
> 
> Huh? Are you referring to:
> 
>  * Note:
>  *   We should flush all tlbs if spte is dropped even though guest is
>  *   responsible for it. Since if we don't,
>  *   kvm_mmu_notifier_invalidate_page
>  *   and kvm_mmu_notifier_invalidate_range_start detect the mapping page
>  *   isn't
>  *   used by guest then tlbs are not flushed, so guest is allowed to
>  *   access the
>  *   freed pages.
>  *   And we increase kvm->tlbs_dirty to delay tlbs flush in this case.
> 
> With an increased dirtied_count the flush can be performed
> by kvm_mmu_notifier_invalidate_page.

Which is what patch 1 does. Your comment regarding sync_page()
above is what is outdated, unless i am missing something.