[PATCH v2 5/5] KVM: MMU: retry #PF for softmmu

Xiao Guangrong
2010-11-12T06:50:42Z

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@cn.fujitsu.com>
---
arch/x86/include/asm/kvm_host.h | 6 ++++++
arch/x86/kvm/mmu.c | 35 ++++++++++++++++++++++++++++++++++-
arch/x86/kvm/x86.c | 15 ++++++++++++++-
virt/kvm/async_pf.c | 1 +
4 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b04c0fa..2cefe00 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -192,6 +192,8 @@ 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
* hash table.
@@ -600,6 +602,7 @@ struct kvm_x86_ops {
struct kvm_arch_async_pf {
u32 token;
gfn_t gfn;
+ struct kvm_mmu_page *root_sp;
bool direct_map;
};

@@ -698,6 +701,8 @@ 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,
@@ -816,6 +821,7 @@ 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 bdb9fa9..4b6d54c 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);
}

@@ -1026,6 +1039,8 @@ static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu,
sp->multimapped = 0;
sp->parent_pte = parent_pte;
kvm_mod_used_mmu_pages(vcpu->kvm, +1);
+ kref_init(&sp->apfs_counter);
+
return sp;
}

@@ -2603,13 +2618,31 @@ static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
error_code & PFERR_WRITE_MASK, gfn, no_apf);
}

+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/x86.c b/arch/x86/kvm/x86.c
index 003a0ca..1ecc1a9 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6169,7 +6169,7 @@ 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;

@@ -6177,6 +6177,10 @@ 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);
}

@@ -6248,6 +6252,12 @@ 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)
{
@@ -6269,6 +6279,9 @@ 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