Re: [PATCH 0/4] Unlocked TLB flush

[Marcelo Tosatti <mtosatti@redhat.com>]

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.