From: Izik Eidus <izike@qumranet.com>
Date: Thu, 20 Mar 2008 16:17:24 +0000 (+0200)
Subject: KVM: MMU: fix dirty bit setting when removing write permissions
X-Git-Tag: v2.6.26-rc1~1028^2~77
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=855149aaa90016c576a0e684361a34f8047307d0;p=linux-2.6

KVM: MMU: fix dirty bit setting when removing write permissions

When mmu_set_spte() checks if a page related to spte should be release as
dirty or clean, it check if the shadow pte was writeble, but in case
rmap_write_protect() is called called it is possible for shadow ptes that were
writeble to become readonly and therefor mmu_set_spte will release the pages
as clean.

This patch fix this issue by marking the page as dirty inside
rmap_write_protect().

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
---

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index a5872b3c46..dd4b95b389 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -626,6 +626,14 @@ static void rmap_write_protect(struct kvm *kvm, u64 gfn)
 		}
 		spte = rmap_next(kvm, rmapp, spte);
 	}
+	if (write_protected) {
+		struct page *page;
+
+		spte = rmap_next(kvm, rmapp, NULL);
+		page = pfn_to_page((*spte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT);
+		SetPageDirty(page);
+	}
+
 	/* check for huge page mappings */
 	rmapp = gfn_to_rmap(kvm, gfn, 1);
 	spte = rmap_next(kvm, rmapp, NULL);