[PATCH v3 3/3] KVM: MMU: retry #PF for softmmu

From: Xiao Guangrong
Date: Tue Nov 30 2010 - 04:33:20 EST

Retry #PF for softmmu only when the current vcpu has the same root shadow page
as the time when #PF occurs. it means they have same paging environment

Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 5 +++++
arch/x86/kvm/mmu.c | 33 ++++++++++++++++++++++++++++++++-
arch/x86/kvm/paging_tmpl.h | 34 +++++++++++++++++++++++-----------
arch/x86/kvm/x86.c | 13 ++++++++++++-
virt/kvm/async_pf.c | 1 +
5 files changed, 73 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 209da89..5acbcab 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -191,6 +191,7 @@ union kvm_mmu_page_role {
struct kvm_mmu_page {
struct list_head link;
struct hlist_node hash_link;
+ struct kref apfs_counter;

/*
* The following two entries are used to key the shadow page in the
@@ -602,6 +603,7 @@ struct kvm_x86_ops {
struct kvm_arch_async_pf {
u32 token;
gfn_t gfn;
+ struct kvm_mmu_page *root_sp;
bool direct_map;
};

@@ -701,6 +703,8 @@ void kvm_inject_nmi(struct kvm_vcpu *vcpu);

int fx_init(struct kvm_vcpu *vcpu);

+struct kvm_mmu_page *get_vcpu_root_sp(struct kvm_vcpu *vcpu, gva_t gva);
+void kvm_mmu_release_apf_sp(struct kvm_mmu_page *sp);
void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu);
void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
const u8 *new, int bytes,
@@ -819,6 +823,7 @@ void kvm_set_shared_msr(unsigned index, u64 val, u64 mask);

bool kvm_is_linear_rip(struct kvm_vcpu *vcpu, unsigned long linear_rip);

+void kvm_arch_clear_async_pf(struct kvm_async_pf *work);
void kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu,
struct kvm_async_pf *work);
void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index f34987d..b9e1681 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -993,6 +993,19 @@ static inline void kvm_mod_used_mmu_pages(struct kvm *kvm, int nr)
percpu_counter_add(&kvm_total_used_mmu_pages, nr);
}

+static void free_shadow_page(struct kref *kref)
+{
+ struct kvm_mmu_page *sp;
+
+ sp = container_of(kref, struct kvm_mmu_page, apfs_counter);
+ kmem_cache_free(mmu_page_header_cache, sp);
+}
+
+void kvm_mmu_release_apf_sp(struct kvm_mmu_page *sp)
+{
+ kref_put(&sp->apfs_counter, free_shadow_page);
+}
+
static void kvm_mmu_free_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
ASSERT(is_empty_shadow_page(sp->spt));
@@ -1001,7 +1014,7 @@ static void kvm_mmu_free_page(struct kvm *kvm, struct kvm_mmu_page *sp)
__free_page(virt_to_page(sp->spt));
if (!sp->role.direct)
__free_page(virt_to_page(sp->gfns));
- kmem_cache_free(mmu_page_header_cache, sp);
+ kvm_mmu_release_apf_sp(sp);
kvm_mod_used_mmu_pages(kvm, -1);
}

@@ -1025,6 +1038,7 @@ static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu,
bitmap_zero(sp->slot_bitmap, KVM_MEMORY_SLOTS + KVM_PRIVATE_MEM_SLOTS);
sp->multimapped = 0;
sp->parent_pte = parent_pte;
+ kref_init(&sp->apfs_counter);
kvm_mod_used_mmu_pages(vcpu->kvm, +1);
return sp;
}
@@ -2603,12 +2617,29 @@ static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
error_code & PFERR_WRITE_MASK, gfn, prefault);
}

+struct kvm_mmu_page *get_vcpu_root_sp(struct kvm_vcpu *vcpu, gva_t gva)
+{
+ struct kvm_shadow_walk_iterator iterator;
+ bool ret;
+
+ shadow_walk_init(&iterator, vcpu, gva);
+ ret = shadow_walk_okay(&iterator);
+ WARN_ON(!ret);
+
+ return page_header(__pa(iterator.sptep));
+}
+
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;
+ if (!arch.direct_map) {
+ arch.root_sp = get_vcpu_root_sp(vcpu, gva);
+ kref_get(&arch.root_sp->apfs_counter);
+ }

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 f04162d..2ca0b67 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,
@@ -285,10 +292,11 @@ 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,
@@ -296,7 +304,7 @@ 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,
@@ -436,7 +444,8 @@ 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;
@@ -510,7 +519,7 @@ 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;
@@ -559,15 +568,18 @@ 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;
}

@@ -597,7 +609,7 @@ 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);
@@ -683,7 +695,7 @@ 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 83ed55f..33dcbce 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6181,7 +6181,7 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
if (!shadow_accessed_mask)
return;

- 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;

@@ -6189,6 +6189,10 @@ 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 &&
+ get_vcpu_root_sp(vcpu, work->gva) != work->arch.root_sp)
+ return;
+
vcpu->arch.mmu.page_fault(vcpu, work->gva, 0, true);
}

@@ -6260,6 +6264,12 @@ static int apf_put_user(struct kvm_vcpu *vcpu, u32 val)
sizeof(val));
}

+void kvm_arch_clear_async_pf(struct kvm_async_pf *work)
+{
+ if (!work->arch.direct_map)
+ kvm_mmu_release_apf_sp(work->arch.root_sp);
+}
+
void kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu,
struct kvm_async_pf *work)
{
@@ -6281,6 +6291,7 @@ void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
struct kvm_async_pf *work)
{
trace_kvm_async_pf_ready(work->arch.token, work->gva);
+ kvm_arch_clear_async_pf(work);
if (is_error_page(work->page))
work->arch.token = ~0; /* broadcast wakeup */
else
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index 74268b4..c3d4788 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -101,6 +101,7 @@ void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
typeof(*work), queue);
cancel_work_sync(&work->work);
list_del(&work->queue);
+ kvm_arch_clear_async_pf(work);
if (!work->done) /* work was canceled */
kmem_cache_free(async_pf_cache, work);
}
--
1.7.0.4
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