[PATCH 1/3] kvm: dont hold pagecount reference for mapped sptes pages

From: Izik Eidus <ieidus@redhat.com>
To: avi@redhat.com
Cc: kvm@vger.kernel.org, aarcange@redhat.com, mtosatti@redhat.com,
	Izik Eidus <ieidus@redhat.com>
Subject: [PATCH 1/3] kvm: dont hold pagecount reference for mapped sptes pages
Date: Wed, 23 Sep 2009 21:47:16 +0300	[thread overview]
Message-ID: <1253731638-24575-2-git-send-email-ieidus@redhat.com> (raw)
In-Reply-To: <1253731638-24575-1-git-send-email-ieidus@redhat.com>

When using mmu notifiers, we are allowed to remove the page count
reference tooken by get_user_pages to a specific page that is mapped
inside the shadow page tables.

This is needed so we can balance the pagecount against mapcount
checking.

(Right now kvm increase the pagecount and does not increase the
mapcount when mapping page into shadow page table entry,
so when comparing pagecount against mapcount, you have no
reliable result.)

Signed-off-by: Izik Eidus <ieidus@redhat.com>
---
 arch/x86/kvm/mmu.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index eca41ae..6c67b23 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -634,9 +634,7 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
 	if (*spte & shadow_accessed_mask)
 		kvm_set_pfn_accessed(pfn);
 	if (is_writeble_pte(*spte))
-		kvm_release_pfn_dirty(pfn);
-	else
-		kvm_release_pfn_clean(pfn);
+		kvm_set_pfn_dirty(pfn);
 	rmapp = gfn_to_rmap(kvm, sp->gfns[spte - sp->spt], sp->role.level);
 	if (!*rmapp) {
 		printk(KERN_ERR "rmap_remove: %p %llx 0->BUG\n", spte, *spte);
@@ -1877,8 +1875,7 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 	page_header_update_slot(vcpu->kvm, sptep, gfn);
 	if (!was_rmapped) {
 		rmap_count = rmap_add(vcpu, sptep, gfn);
-		if (!is_rmap_spte(*sptep))
-			kvm_release_pfn_clean(pfn);
+		kvm_release_pfn_clean(pfn);
 		if (rmap_count > RMAP_RECYCLE_THRESHOLD)
 			rmap_recycle(vcpu, sptep, gfn);
 	} else {
-- 
1.5.6.5

