2 files changed, 76 insertions, 31 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 88fce6ab4bbd..32345241e620 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -748,7 +748,7 @@ struct kvm_vcpu_arch {
 		u8 preempted;
 		u64 msr_val;
 		u64 last_steal;
-		struct gfn_to_pfn_cache cache;
+		struct gfn_to_hva_cache cache;
 	} st;
 
 	u64 l1_tsc_offset;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ac83d873d65b..e7d2ef944cc8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3260,8 +3260,11 @@ static void kvm_vcpu_flush_tlb_guest(struct kvm_vcpu *vcpu)
 
 static void record_steal_time(struct kvm_vcpu *vcpu)
 {
-	struct kvm_host_map map;
-	struct kvm_steal_time *st;
+	struct gfn_to_hva_cache *ghc = &vcpu->arch.st.cache;
+	struct kvm_steal_time __user *st;
+	struct kvm_memslots *slots;
+	u64 steal;
+	u32 version;
 
 	if (kvm_xen_msr_enabled(vcpu->kvm)) {
 		kvm_xen_runstate_set_running(vcpu);
@@ -3271,47 +3274,83 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
 	if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
 		return;
 
-	/* -EAGAIN is returned in atomic context so we can just return. */
-	if (kvm_map_gfn(vcpu, vcpu->arch.st.msr_val >> PAGE_SHIFT,
-			&map, &vcpu->arch.st.cache, false))
+	if (WARN_ON_ONCE(current->mm != vcpu->kvm->mm))
 		return;
 
-	st = map.hva +
-		offset_in_page(vcpu->arch.st.msr_val & KVM_STEAL_VALID_BITS);
+	slots = kvm_memslots(vcpu->kvm);
+
+	if (unlikely(slots->generation != ghc->generation ||
+		     kvm_is_error_hva(ghc->hva) || !ghc->memslot)) {
+		gfn_t gfn = vcpu->arch.st.msr_val & KVM_STEAL_VALID_BITS;
+
+		/* We rely on the fact that it fits in a single page. */
+		BUILD_BUG_ON((sizeof(*st) - 1) & KVM_STEAL_VALID_BITS);
+
+		if (kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc, gfn, sizeof(*st)) ||
+		    kvm_is_error_hva(ghc->hva) || !ghc->memslot)
+			return;
+	}
+
+	st = (struct kvm_steal_time __user *)ghc->hva;
+	if (!user_access_begin(st, sizeof(*st)))
+		return;
 
 	/*
 	 * Doing a TLB flush here, on the guest's behalf, can avoid
 	 * expensive IPIs.
 	 */
 	if (guest_pv_has(vcpu, KVM_FEATURE_PV_TLB_FLUSH)) {
-		u8 st_preempted = xchg(&st->preempted, 0);
+		u8 st_preempted = 0;
+		int err = -EFAULT;
+
+		asm volatile("1: xchgb %0, %2\n"
+			     "xor %1, %1\n"
+			     "2:\n"
+			     _ASM_EXTABLE_UA(1b, 2b)
+			     : "+r" (st_preempted),
+			       "+&r" (err)
+			     : "m" (st->preempted));
+		if (err)
+			goto out;
+
+		user_access_end();
+
+		vcpu->arch.st.preempted = 0;
 
 		trace_kvm_pv_tlb_flush(vcpu->vcpu_id,
 				       st_preempted & KVM_VCPU_FLUSH_TLB);
 		if (st_preempted & KVM_VCPU_FLUSH_TLB)
 			kvm_vcpu_flush_tlb_guest(vcpu);
+
+		if (!user_access_begin(st, sizeof(*st)))
+			goto dirty;
 	} else {
-		st->preempted = 0;
+		unsafe_put_user(0, &st->preempted, out);
+		vcpu->arch.st.preempted = 0;
 	}
 
-	vcpu->arch.st.preempted = 0;
-
-	if (st->version & 1)
-		st->version += 1;  /* first time write, random junk */
+	unsafe_get_user(version, &st->version, out);
+	if (version & 1)
+		version += 1;  /* first time write, random junk */
 
-	st->version += 1;
+	version += 1;
+	unsafe_put_user(version, &st->version, out);
 
 	smp_wmb();
 
-	st->steal += current->sched_info.run_delay -
+	unsafe_get_user(steal, &st->steal, out);
+	steal += current->sched_info.run_delay -
 		vcpu->arch.st.last_steal;
 	vcpu->arch.st.last_steal = current->sched_info.run_delay;
+	unsafe_put_user(steal, &st->steal, out);
 
-	smp_wmb();
-
-	st->version += 1;
+	version += 1;
+	unsafe_put_user(version, &st->version, out);
 
-	kvm_unmap_gfn(vcpu, &map, &vcpu->arch.st.cache, true, false);
+ out:
+	user_access_end();
+ dirty:
+	mark_page_dirty_in_slot(vcpu->kvm, ghc->memslot, gpa_to_gfn(ghc->gpa));
 }
 
 int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
@@ -4351,8 +4390,10 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 
 static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
 {
-	struct kvm_host_map map;
-	struct kvm_steal_time *st;
+	struct gfn_to_hva_cache *ghc = &vcpu->arch.st.cache;
+	struct kvm_steal_time __user *st;
+	struct kvm_memslots *slots;
+	static const u8 preempted = KVM_VCPU_PREEMPTED;
 
 	if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
 		return;
@@ -4360,16 +4401,23 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
 	if (vcpu->arch.st.preempted)
 		return;
 
-	if (kvm_map_gfn(vcpu, vcpu->arch.st.msr_val >> PAGE_SHIFT, &map,
-			&vcpu->arch.st.cache, true))
+	/* This happens on process exit */
+	if (unlikely(current->mm != vcpu->kvm->mm))
 		return;
 
-	st = map.hva +
-		offset_in_page(vcpu->arch.st.msr_val & KVM_STEAL_VALID_BITS);
+	slots = kvm_memslots(vcpu->kvm);
+
+	if (unlikely(slots->generation != ghc->generation ||
+		     kvm_is_error_hva(ghc->hva) || !ghc->memslot))
+		return;
 
-	st->preempted = vcpu->arch.st.preempted = KVM_VCPU_PREEMPTED;
+	st = (struct kvm_steal_time __user *)ghc->hva;
+	BUILD_BUG_ON(sizeof(st->preempted) != sizeof(preempted));
 
-	kvm_unmap_gfn(vcpu, &map, &vcpu->arch.st.cache, true, true);
+	if (!copy_to_user_nofault(&st->preempted, &preempted, sizeof(preempted)))
+		vcpu->arch.st.preempted = KVM_VCPU_PREEMPTED;
+
+	mark_page_dirty_in_slot(vcpu->kvm, ghc->memslot, gpa_to_gfn(ghc->gpa));
 }
 
 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
@@ -11022,11 +11070,8 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
 
 void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
 {
-	struct gfn_to_pfn_cache *cache = &vcpu->arch.st.cache;
 	int idx;
 
-	kvm_release_pfn(cache->pfn, cache->dirty, cache);
-
 	kvmclock_reset(vcpu);
 
 	static_call(kvm_x86_vcpu_free)(vcpu);