linux-kernel - [PATCH 6/9] KVM: MMU: Add missing dirty bit

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Message-Id: <20070105075545.83E2F250048@il.qumranet.com>
Date:	Fri, 05 Jan 2007 07:55:45 -0000
From:	Avi Kivity <avi@...ranet.com>
To:	kvm-devel@...ts.sourceforge.net
Cc:	linux-kernel@...r.kernel.org, akpm@...l.org, mingo@...e.hu
Subject: [PATCH 6/9] KVM: MMU: Add missing dirty bit

If we emulate a write, we fail to set the dirty bit on the guest pte, leading
the guest to believe the page is clean, and thus lose data.  Bad.

Fix by setting the guest pte dirty bit under such conditions.

Signed-off-by: Avi Kivity <avi@...ranet.com>

Index: linux-2.6/drivers/kvm/paging_tmpl.h
===================================================================
--- linux-2.6.orig/drivers/kvm/paging_tmpl.h
+++ linux-2.6/drivers/kvm/paging_tmpl.h
@@ -317,6 +317,7 @@ static int FNAME(fix_write_pf)(struct kv
 	} else if (kvm_mmu_lookup_page(vcpu, gfn)) {
 		pgprintk("%s: found shadow page for %lx, marking ro\n",
 			 __FUNCTION__, gfn);
+		*guest_ent |= PT_DIRTY_MASK;
 		*write_pt = 1;
 		return 0;
 	}
-
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