linux-kernel - [PATCH v5 5/9] KVM: MMU: introduce SPTE_MMU

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: <4FBCA5E5.4080402@linux.vnet.ibm.com>
Date:	Wed, 23 May 2012 16:55:01 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
CC:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: [PATCH v5 5/9] KVM: MMU: introduce SPTE_MMU_WRITEABLE bit

This bit indicates whether the spte can be writable on MMU, that means
the corresponding gpte is writable and the corresponding gfn is not
protected by shadow page protection

Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
---
 arch/x86/kvm/mmu.c |   43 +++++++++++++++++++++++++++++--------------
 1 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 4810992..bd837f3 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -145,7 +145,8 @@ module_param(dbg, bool, 0644);
 #define CREATE_TRACE_POINTS
 #include "mmutrace.h"

-#define SPTE_HOST_WRITEABLE (1ULL << PT_FIRST_AVAIL_BITS_SHIFT)
+#define SPTE_HOST_WRITEABLE	(1ULL << PT_FIRST_AVAIL_BITS_SHIFT)
+#define SPTE_MMU_WRITEABLE	(1ULL << (PT_FIRST_AVAIL_BITS_SHIFT + 1))

 #define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)

@@ -1065,32 +1066,45 @@ static void drop_spte(struct kvm *kvm, u64 *sptep)
 		rmap_remove(kvm, sptep);
 }

+static bool spte_can_be_writable(u64 spte)
+{
+	u64 mask = SPTE_HOST_WRITEABLE | SPTE_MMU_WRITEABLE;
+
+	return (spte & mask) == mask;
+}
+
 /* Return true if the spte is dropped. */
-static bool spte_write_protect(struct kvm *kvm, u64 *sptep, bool *flush)
+static bool
+spte_write_protect(struct kvm *kvm, u64 *sptep, bool *flush, bool pt_protect)
 {
 	u64 spte = *sptep;

-	if (!is_writable_pte(spte))
+	if (!is_writable_pte(spte) &&
+	      !(pt_protect && spte_can_be_writable(spte)))
 		return false;

 	rmap_printk("rmap_write_protect: spte %p %llx\n", sptep, *sptep);

-	*flush |= true;
 	if (is_large_pte(spte)) {
 		WARN_ON(page_header(__pa(sptep))->role.level ==
 		       PT_PAGE_TABLE_LEVEL);
+
+		*flush |= true;
 		drop_spte(kvm, sptep);
 		--kvm->stat.lpages;
 		return true;
 	}

+	if (pt_protect)
+		spte &= ~SPTE_MMU_WRITEABLE;
 	spte = spte & ~PT_WRITABLE_MASK;
-	mmu_spte_update(sptep, spte);
+
+	*flush = mmu_spte_update(sptep, spte);
 	return false;
 }

-static bool
-__rmap_write_protect(struct kvm *kvm, unsigned long *rmapp, int level)
+static bool __rmap_write_protect(struct kvm *kvm, unsigned long *rmapp,
+				 int level, bool pt_protect)
 {
 	u64 *sptep;
 	struct rmap_iterator iter;
@@ -1098,7 +1112,7 @@ __rmap_write_protect(struct kvm *kvm, unsigned long *rmapp, int level)

 	for (sptep = rmap_get_first(*rmapp, &iter); sptep;) {
 		BUG_ON(!(*sptep & PT_PRESENT_MASK));
-		if (spte_write_protect(kvm, sptep, &flush)) {
+		if (spte_write_protect(kvm, sptep, &flush, pt_protect)) {
 			sptep = rmap_get_first(*rmapp, &iter);
 			continue;
 		}
@@ -1127,7 +1141,7 @@ void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,

 	while (mask) {
 		rmapp = &slot->rmap[gfn_offset + __ffs(mask)];
-		__rmap_write_protect(kvm, rmapp, PT_PAGE_TABLE_LEVEL);
+		__rmap_write_protect(kvm, rmapp, PT_PAGE_TABLE_LEVEL, false);

 		/* clear the first set bit */
 		mask &= mask - 1;
@@ -1146,7 +1160,7 @@ static bool rmap_write_protect(struct kvm *kvm, u64 gfn)
 	for (i = PT_PAGE_TABLE_LEVEL;
 	     i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++i) {
 		rmapp = __gfn_to_rmap(gfn, i, slot);
-		write_protected |= __rmap_write_protect(kvm, rmapp, i);
+		write_protected |= __rmap_write_protect(kvm, rmapp, i, true);
 	}

 	return write_protected;
@@ -2284,8 +2298,10 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 		spte |= shadow_x_mask;
 	else
 		spte |= shadow_nx_mask;
+
 	if (pte_access & ACC_USER_MASK)
 		spte |= shadow_user_mask;
+
 	if (level > PT_PAGE_TABLE_LEVEL)
 		spte |= PT_PAGE_SIZE_MASK;
 	if (tdp_enabled)
@@ -2310,7 +2326,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 			goto done;
 		}

-		spte |= PT_WRITABLE_MASK;
+		spte |= PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE;

 		if (!vcpu->arch.mmu.direct_map
 		    && !(pte_access & ACC_WRITE_MASK)) {
@@ -2339,8 +2355,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 				 __func__, gfn);
 			ret = 1;
 			pte_access &= ~ACC_WRITE_MASK;
-			if (is_writable_pte(spte))
-				spte &= ~PT_WRITABLE_MASK;
+			spte &= ~(PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE);
 		}
 	}

@@ -3921,7 +3936,7 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
 			      !is_last_spte(pt[i], sp->role.level))
 				continue;

-			spte_write_protect(kvm, &pt[i], &flush);
+			spte_write_protect(kvm, &pt[i], &flush, false);
 		}
 	}
 	kvm_flush_remote_tlbs(kvm);
-- 
1.7.7.6

--
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/