linux-kernel - [PATCH 3/3] KVM: MMU: mark page dirty only when page is really written

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4C4E53F7.7050108@cn.fujitsu.com>
Date:	Tue, 27 Jul 2010 11:35:19 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>
Subject: [PATCH 3/3] KVM: MMU: mark page dirty only when page is really written

Mark page dirty only when this page is really written, it's more exacter,
and also can fix dirty page marking in speculation path

Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
---
 arch/x86/kvm/mmu.c |   47 ++++++++++++++++++++++++++++-------------------
 1 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index dd6c192..bcc2173 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -311,24 +311,42 @@ static bool spte_bits_lost(u64 spte)
 	if (!is_shadow_present_pte(spte))
 		return false;
 
-	if (spte & shadow_accessed_mask)
+	if (spte & shadow_accessed_mask &&
+	      (!is_writable_pte(spte) || spte & shadow_dirty_mask))
 		return false;
 
 	return true;
 }
 
+static bool spte_is_bit_cleared(u64 old_spte, u64 new_spte, u64 bit_mask)
+{
+	return old_spte & bit_mask && !(new_spte & bit_mask);
+}
+
 static void update_spte(u64 *sptep, u64 new_spte)
 {
-	u64 old_spte;
+	u64 mask, old_spte = *sptep;
+
+	WARN_ON(!is_rmap_spte(new_spte));
 
-	if (!shadow_accessed_mask || (new_spte & shadow_accessed_mask) ||
-	      !is_rmap_spte(*sptep))
+	new_spte |= old_spte & shadow_dirty_mask;
+
+	mask = shadow_accessed_mask;
+	if (is_writable_pte(old_spte))
+		mask |= shadow_dirty_mask;
+
+	if (!spte_bits_lost(old_spte) || (new_spte & mask) == mask)
 		__set_spte(sptep, new_spte);
-	else {
+	else
 		old_spte = __xchg_spte(sptep, new_spte);
-		if (old_spte & shadow_accessed_mask)
-			kvm_set_pfn_accessed(spte_to_pfn(old_spte));
-	}
+
+	if (!shadow_accessed_mask)
+		return;
+
+	if (spte_is_bit_cleared(old_spte, new_spte, shadow_accessed_mask))
+		kvm_set_pfn_accessed(spte_to_pfn(old_spte));
+	if (spte_is_bit_cleared(old_spte, new_spte, shadow_dirty_mask))
+		kvm_set_pfn_dirty(spte_to_pfn(old_spte));
 }
 
 static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
@@ -708,7 +726,7 @@ static void set_spte_track_bits(u64 *sptep, u64 new_spte)
 	pfn = spte_to_pfn(old_spte);
 	if (!shadow_accessed_mask || old_spte & shadow_accessed_mask)
 		kvm_set_pfn_accessed(pfn);
-	if (is_writable_pte(old_spte))
+	if (!shadow_dirty_mask || old_spte & shadow_dirty_mask)
 		kvm_set_pfn_dirty(pfn);
 }
 
@@ -763,13 +781,6 @@ static int rmap_write_protect(struct kvm *kvm, u64 gfn)
 		}
 		spte = rmap_next(kvm, rmapp, spte);
 	}
-	if (write_protected) {
-		pfn_t pfn;
-
-		spte = rmap_next(kvm, rmapp, NULL);
-		pfn = spte_to_pfn(*spte);
-		kvm_set_pfn_dirty(pfn);
-	}
 
 	/* check for huge page mappings */
 	for (i = PT_DIRECTORY_LEVEL;
@@ -1942,7 +1953,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 	 * whether the guest actually used the pte (in order to detect
 	 * demand paging).
 	 */
-	spte = shadow_base_present_pte | shadow_dirty_mask;
+	spte = shadow_base_present_pte;
 	if (!speculative)
 		spte |= shadow_accessed_mask;
 	if (!dirty)
@@ -2003,8 +2014,6 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 		mark_page_dirty(vcpu->kvm, gfn);
 
 set_pte:
-	if (is_writable_pte(*sptep) && !is_writable_pte(spte))
-		kvm_set_pfn_dirty(pfn);
 	update_spte(sptep, spte);
 done:
 	return ret;
-- 
1.6.1.2


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/