kvm: Fix page ageing bugs

1. We were calling clear_flush_young_notify in unmap_one, but we are
within an mmu notifier invalidate range scope. The spte exists no more
(due to range_start) and the accessed bit info has already been
propagated (due to kvm_pfn_set_accessed). Simply call
clear_flush_young.

2. We clear_flush_young on a primary MMU PMD, but this may be mapped
as a collection of PTEs by the secondary MMU (e.g. during log-dirty).
This required expanding the interface of the clear_flush_young mmu
notifier, so a lot of code has been trivially touched.

3. In the absence of shadow_accessed_mask (e.g. EPT A bit), we emulate
the access bit by blowing the spte. This requires proper synchronizing
with MMU notifier consumers, like every other removal of spte's does.

Signed-off-by: Andres Lagar-Cavilla <andreslc@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index 3e8491c..bc74e00 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1355,7 +1355,11 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
 			continue;	/* don't unmap */
 		}
 
-		if (ptep_clear_flush_young_notify(vma, address, pte))
+		/*
+		 * No need for _notify because we're within an
+		 * mmu_notifier_invalidate_range_ {start|end} scope.
+		 */
+		if (ptep_clear_flush_young(vma, address, pte))
 			continue;
 
 		/* Nuke the page table entry. */