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Message-ID: <5097ACD7.5030201@linux.vnet.ibm.com>
Date: Mon, 05 Nov 2012 20:11:03 +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 3/5] KVM: MMU: simplify set_spte
It is more cleaner if we can update pte_access fist then set spte according
to pte_access, also introduce gfn_need_write_protect to check whether the
gfn need to be write-protected
Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
---
arch/x86/kvm/mmu.c | 109 ++++++++++++++++++++++++++++++++--------------------
1 files changed, 67 insertions(+), 42 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 4ea731e..49957df 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2329,6 +2329,63 @@ static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
return 0;
}
+static bool gfn_need_write_protect(struct kvm_vcpu *vcpu, u64 *sptep,
+ int level, gfn_t gfn, bool can_unsync)
+{
+ /*
+ * Optimization: for pte sync, if spte was writable the hash
+ * lookup is unnecessary (and expensive). Write protection
+ * is responsibility of mmu_get_page / kvm_sync_page.
+ * Same reasoning can be applied to dirty page accounting.
+ */
+ if (!can_unsync && is_writable_pte(*sptep))
+ return false;
+
+ if ((level > PT_PAGE_TABLE_LEVEL &&
+ has_wrprotected_page(vcpu->kvm, gfn, level)) ||
+ mmu_need_write_protect(vcpu, gfn, can_unsync))
+ return true;
+
+ return false;
+}
+
+/* The return value indicates whether the @gfn need to be write protected. */
+static bool vcpu_adjust_access(struct kvm_vcpu *vcpu, u64 *sptep,
+ unsigned *pte_access, int user_fault,
+ int write_fault, int level, gfn_t gfn,
+ bool can_unsync, bool host_writable)
+{
+ bool ret = false;
+ unsigned access = *pte_access;
+
+ if (!host_writable)
+ access &= ~ACC_WRITE_MASK;
+
+ if (!(access & ACC_WRITE_MASK) && (!vcpu->arch.mmu.direct_map &&
+ write_fault && !is_write_protection(vcpu) && !user_fault)) {
+ access |= ACC_WRITE_MASK;
+ access &= ~ACC_USER_MASK;
+
+ /*
+ * If we converted a user page to a kernel page,
+ * so that the kernel can write to it when cr0.wp=0,
+ * then we should prevent the kernel from executing it
+ * if SMEP is enabled.
+ */
+ if (kvm_read_cr4_bits(vcpu, X86_CR4_SMEP))
+ access &= ~ACC_EXEC_MASK;
+ }
+
+ if ((access & ACC_WRITE_MASK) &&
+ gfn_need_write_protect(vcpu, sptep, level, gfn, can_unsync)) {
+ access &= ~ACC_WRITE_MASK;
+ ret = true;
+ }
+
+ *pte_access = access;
+ return ret;
+}
+
static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
unsigned pte_access, int user_fault,
int write_fault, int level,
@@ -2341,6 +2398,9 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
if (set_mmio_spte(sptep, gfn, pfn, pte_access))
return 0;
+ ret = vcpu_adjust_access(vcpu, sptep, &pte_access, user_fault,
+ write_fault, level, gfn, can_unsync, host_writable);
+
spte = PT_PRESENT_MASK;
if (!speculative)
spte |= shadow_accessed_mask;
@@ -2353,61 +2413,26 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
if (pte_access & ACC_USER_MASK)
spte |= shadow_user_mask;
+ if (pte_access & ACC_WRITE_MASK) {
+ spte |= PT_WRITABLE_MASK;
+ spte |= SPTE_MMU_WRITEABLE;
+ }
+
if (level > PT_PAGE_TABLE_LEVEL)
spte |= PT_PAGE_SIZE_MASK;
+
if (tdp_enabled)
spte |= kvm_x86_ops->get_mt_mask(vcpu, gfn,
kvm_is_mmio_pfn(pfn));
if (host_writable)
spte |= SPTE_HOST_WRITEABLE;
- else
- pte_access &= ~ACC_WRITE_MASK;
spte |= (u64)pfn << PAGE_SHIFT;
- if ((pte_access & ACC_WRITE_MASK)
- || (!vcpu->arch.mmu.direct_map && write_fault
- && !is_write_protection(vcpu) && !user_fault)) {
- spte |= PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE;
-
- if (!vcpu->arch.mmu.direct_map
- && !(pte_access & ACC_WRITE_MASK)) {
- spte &= ~PT_USER_MASK;
- /*
- * If we converted a user page to a kernel page,
- * so that the kernel can write to it when cr0.wp=0,
- * then we should prevent the kernel from executing it
- * if SMEP is enabled.
- */
- if (kvm_read_cr4_bits(vcpu, X86_CR4_SMEP))
- spte |= PT64_NX_MASK;
- }
-
- /*
- * Optimization: for pte sync, if spte was writable the hash
- * lookup is unnecessary (and expensive). Write protection
- * is responsibility of mmu_get_page / kvm_sync_page.
- * Same reasoning can be applied to dirty page accounting.
- */
- if (!can_unsync && is_writable_pte(*sptep))
- goto set_pte;
-
- if ((level > PT_PAGE_TABLE_LEVEL &&
- has_wrprotected_page(vcpu->kvm, gfn, level)) ||
- mmu_need_write_protect(vcpu, gfn, can_unsync)) {
- pgprintk("%s: found shadow page for %llx, marking ro\n",
- __func__, gfn);
- ret = 1;
- pte_access &= ~ACC_WRITE_MASK;
- spte &= ~(PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE);
- }
- }
-
- if (pte_access & ACC_WRITE_MASK)
+ if (is_writable_pte(spte))
mark_page_dirty(vcpu->kvm, gfn);
-set_pte:
if (mmu_spte_update(sptep, spte))
kvm_flush_remote_tlbs(vcpu->kvm);
return ret;
--
1.7.7.6
--
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