[PATCH v3 2/3] KVM: MMU: fix accessed bit set on prefault path

Xiao Guangrong
2010-11-30T09:31:43Z

Retry #PF is the speculative path, so don't set the accessed bit,
especially, stop prefault if shadow_accessed_mask = 0

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/mmu.c | 12 +++++++-----
arch/x86/kvm/x86.c | 3 +++
3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a4c5352..209da89 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -632,6 +632,7 @@ int kvm_pv_mmu_op(struct kvm_vcpu *vcpu, unsigned long bytes,
u8 kvm_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn);

extern bool tdp_enabled;
+extern u64 __read_mostly shadow_accessed_mask;

enum emulation_result {
EMULATE_DONE, /* no further processing */
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 5b71415..f34987d 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -199,8 +199,8 @@ static u64 __read_mostly shadow_notrap_nonpresent_pte;
static u64 __read_mostly shadow_nx_mask;
static u64 __read_mostly shadow_x_mask; /* mutual exclusive with nx_mask */
static u64 __read_mostly shadow_user_mask;
-static u64 __read_mostly shadow_accessed_mask;
static u64 __read_mostly shadow_dirty_mask;
+u64 __read_mostly shadow_accessed_mask;

static inline u64 rsvd_bits(int s, int e)
{
@@ -2214,7 +2214,8 @@ static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep)
}

static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
- int map_writable, int level, gfn_t gfn, pfn_t pfn)
+ int map_writable, int level, gfn_t gfn, pfn_t pfn,
+ bool prefault)
{
struct kvm_shadow_walk_iterator iterator;
struct kvm_mmu_page *sp;
@@ -2229,7 +2230,7 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
pte_access &= ~ACC_WRITE_MASK;
mmu_set_spte(vcpu, iterator.sptep, ACC_ALL, pte_access,
0, write, 1, &pt_write,
- level, gfn, pfn, false, map_writable);
+ level, gfn, pfn, prefault, map_writable);
direct_pte_prefetch(vcpu, iterator.sptep);
++vcpu->stat.pf_fixed;
break;
@@ -2321,7 +2322,8 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn,
if (mmu_notifier_retry(vcpu, mmu_seq))
goto out_unlock;
kvm_mmu_free_some_pages(vcpu);
- r = __direct_map(vcpu, v, write, map_writable, level, gfn, pfn);
+ r = __direct_map(vcpu, v, write, map_writable, level, gfn, pfn,
+ prefault);
spin_unlock(&vcpu->kvm->mmu_lock);

@@ -2683,7 +2685,7 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
goto out_unlock;
kvm_mmu_free_some_pages(vcpu);
r = __direct_map(vcpu, gpa, write, map_writable,
- level, gfn, pfn);
+ level, gfn, pfn, prefault);
spin_unlock(&vcpu->kvm->mmu_lock);

return r;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 410d2d1..83ed55f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6178,6 +6178,9 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
{
int r;

+ if (!shadow_accessed_mask)
+ return;
+
if (!vcpu->arch.mmu.direct_map || !work->arch.direct_map ||
is_error_page(work->page))
return;
--
1.7.0.4