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

[Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>]

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              |   33 ++++++++++++++++++++++++++++++++-
 arch/x86/kvm/x86.c              |   16 ++++++++++++++--
 virt/kvm/async_pf.c             |    1 +
 4 files changed, 53 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 7f20f2c..b99ef7d 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;
 };
 
 extern struct kvm_x86_ops *kvm_x86_ops;
@@ -697,6 +700,8 @@ 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,
@@ -822,6 +827,7 @@ void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
 void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu,
 			       struct kvm_async_pf *work);
 bool kvm_arch_can_inject_async_page_present(struct kvm_vcpu *vcpu);
+void kvm_arch_clear_async_pf(struct kvm_async_pf *work);
 extern bool kvm_find_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn);
 
 #endif /* _ASM_X86_KVM_HOST_H */
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index f3fad4f..60cc9f9 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 +1039,7 @@ 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;
 }
 
@@ -2597,11 +2611,28 @@ static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
 			     error_code & PFERR_WRITE_MASK, gfn);
 }
 
+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;
+	if (!tdp_enabled) {
+		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 aacc5eb..72d672f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6174,14 +6174,17 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
 {
 	int r;
 
-	if (!tdp_enabled || is_error_page(work->page))
+	if (is_error_page(work->page))
 		return;
 
 	r = kvm_mmu_reload(vcpu);
+
 	if (unlikely(r))
 		return;
 
-	vcpu->arch.mmu.page_fault(vcpu, work->gva, 0, true);
+	if (tdp_enabled ||
+	      get_vcpu_root_sp(vcpu, work->gva) == work->arch.root_sp)
+		vcpu->arch.mmu.page_fault(vcpu, work->gva, 0, true);
 }
 
 static inline u32 kvm_async_pf_hash_fn(gfn_t gfn)
@@ -6269,10 +6272,19 @@ void kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu,
 	}
 }
 
+void kvm_arch_clear_async_pf(struct kvm_async_pf *work)
+{
+	if (!tdp_enabled)
+		kvm_mmu_release_apf_sp(work->arch.root_sp);
+}
+
 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