linux-kernel - [PATCH 30/35] KVM: MMU: fix dirty bit setting when removing write permissions

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Message-Id: <1207251170-5013-31-git-send-email-avi@qumranet.com>
Date:	Thu,  3 Apr 2008 22:32:45 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	kvm-devel@...ts.sourceforge.net
Cc:	linux-kernel@...r.kernel.org, Izik Eidus <izike@...ranet.com>
Subject: [PATCH 30/35] KVM: MMU: fix dirty bit setting when removing write permissions

From: Izik Eidus <izike@...ranet.com>

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@...ranet.com>
Signed-off-by: Avi Kivity <avi@...ranet.com>
---
 arch/x86/kvm/mmu.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index a5872b3..dd4b95b 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);
-- 
1.5.4.5

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