[PATCH v4 3/3] KVM: MMU: retry #PF for softmmu

Xiao Guangrong
2010-12-02T09:46:46Z

Retry #PF for softmmu only when the current vcpu has the same cr3 as the time
when #PF occurs

Changelog:
Just compare cr3 value since It's harmless to instantiate an spte for an
unused translation from Marcelo's comment

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/mmu.c | 2 ++
arch/x86/kvm/paging_tmpl.h | 34 +++++++++++++++++++++++-----------
arch/x86/kvm/x86.c | 6 +++++-
4 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a0c066e..1e876e5 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -602,6 +602,7 @@ struct kvm_x86_ops {
struct kvm_arch_async_pf {
u32 token;
gfn_t gfn;
+ unsigned long cr3;
bool direct_map;
};

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index c6bb449..3f0d9a0 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2607,9 +2607,11 @@ static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
static int kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn)
{
struct kvm_arch_async_pf arch;
+
arch.token = (vcpu->arch.apf.id++ << 12) | vcpu->vcpu_id;
arch.gfn = gfn;
arch.direct_map = vcpu->arch.mmu.direct_map;
+ arch.cr3 = vcpu->arch.mmu.get_cr3(vcpu);

return kvm_setup_async_pf(vcpu, gva, gfn, &arch);
}
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 23275d0..437e11a 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -116,7 +116,7 @@ static unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, pt_element_t gpte)
*/
static int FNAME(walk_addr_generic)(struct guest_walker *walker,
struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
- gva_t addr, u32 access)
+ gva_t addr, u32 access, bool prefault)
{
pt_element_t pte;
gfn_t table_gfn;
@@ -194,6 +194,13 @@ walk:
#endif

if (!eperm && !rsvd_fault && !(pte & PT_ACCESSED_MASK)) {
+ /*
+ * Don't set gpte accessed bit if it's on
+ * speculative path.
+ */
+ if (prefault)
+ goto error;
+
trace_kvm_mmu_set_accessed_bit(table_gfn, index,
sizeof(pte));
if (FNAME(cmpxchg_gpte)(vcpu->kvm, table_gfn,
@@ -287,10 +294,11 @@ error:
}

static int FNAME(walk_addr)(struct guest_walker *walker,
- struct kvm_vcpu *vcpu, gva_t addr, u32 access)
+ struct kvm_vcpu *vcpu, gva_t addr,
+ u32 access, bool prefault)
{
return FNAME(walk_addr_generic)(walker, vcpu, &vcpu->arch.mmu, addr,
- access);
+ access, prefault);
}

static int FNAME(walk_addr_nested)(struct guest_walker *walker,
@@ -298,7 +306,7 @@ static int FNAME(walk_addr_nested)(struct guest_walker *walker,
u32 access)
{
return FNAME(walk_addr_generic)(walker, vcpu, &vcpu->arch.nested_mmu,
- addr, access);
+ addr, access, false);
}

static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu,
@@ -438,7 +446,8 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, struct guest_walker *gw,
static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
struct guest_walker *gw,
int user_fault, int write_fault, int hlevel,
- int *ptwrite, pfn_t pfn, bool map_writable)
+ int *ptwrite, pfn_t pfn, bool map_writable,
+ bool prefault)
{
unsigned access = gw->pt_access;
struct kvm_mmu_page *sp = NULL;
@@ -512,7 +521,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,

mmu_set_spte(vcpu, it.sptep, access, gw->pte_access & access,
user_fault, write_fault, dirty, ptwrite, it.level,
- gw->gfn, pfn, false, map_writable);
+ gw->gfn, pfn, prefault, map_writable);
FNAME(pte_prefetch)(vcpu, gw, it.sptep);

return it.sptep;
@@ -561,15 +570,18 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
/*
* Look up the guest pte for the faulting address.
*/
- r = FNAME(walk_addr)(&walker, vcpu, addr, error_code);
+ r = FNAME(walk_addr)(&walker, vcpu, addr, error_code, prefault);

/*
* The page is not mapped by the guest. Let the guest handle it.
*/
if (!r) {
pgprintk("%s: guest page fault\n", __func__);
- inject_page_fault(vcpu);
- vcpu->arch.last_pt_write_count = 0; /* reset fork detector */
+ if (!prefault) {
+ inject_page_fault(vcpu);
+ /* reset fork detector */
+ vcpu->arch.last_pt_write_count = 0;
+ }
return 0;
}

@@ -599,7 +611,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
trace_kvm_mmu_audit(vcpu, AUDIT_PRE_PAGE_FAULT);
kvm_mmu_free_some_pages(vcpu);
sptep = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault,
- level, &write_pt, pfn, map_writable);
+ level, &write_pt, pfn, map_writable, prefault);
(void)sptep;
pgprintk("%s: shadow pte %p %llx ptwrite %d\n", __func__,
sptep, *sptep, write_pt);
@@ -685,7 +697,7 @@ static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr, u32 access,
gpa_t gpa = UNMAPPED_GVA;
int r;

- r = FNAME(walk_addr)(&walker, vcpu, vaddr, access);
+ r = FNAME(walk_addr)(&walker, vcpu, vaddr, access, false);

if (r) {
gpa = gfn_to_gpa(walker.gfn);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bfd2878..de5e57b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6183,7 +6183,7 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
{
int r;

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

@@ -6191,6 +6191,10 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
if (unlikely(r))
return;

+ if (!vcpu->arch.mmu.direct_map &&
+ work->arch.cr3 != vcpu->arch.mmu.get_cr3(vcpu))
+ return;
+
vcpu->arch.mmu.page_fault(vcpu, work->gva, 0, true);
}

--
1.7.0.4