From 214b0a88c46d5f32d80abe0d1bc2eea1cbd38f11 Mon Sep 17 00:00:00 2001
From: Metin Kaya <metikaya@amazon.com>
Date: Mon, 21 Mar 2022 11:05:32 +0000
Subject: [PATCH 1/9] KVM: x86/xen: add support for 32-bit guests in
 SCHEDOP_poll

This patch introduces compat version of struct sched_poll for
SCHEDOP_poll sub-operation of sched_op hypercall, reads correct amount
of data (16 bytes in 32-bit case, 24 bytes otherwise) by using new
compat_sched_poll struct, copies it to sched_poll properly, and lets
rest of the code run as is.

Signed-off-by: Metin Kaya <metikaya@amazon.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
---
 arch/x86/kvm/xen.c | 33 +++++++++++++++++++++++++++++----
 arch/x86/kvm/xen.h |  7 +++++++
 2 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 9187d024d0066..3e434dc339fb5 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1201,20 +1201,45 @@ static bool kvm_xen_schedop_poll(struct kvm_vcpu *vcpu, bool longmode,
 	evtchn_port_t port, *ports;
 	gpa_t gpa;
 
-	if (!longmode || !lapic_in_kernel(vcpu) ||
+	if (!lapic_in_kernel(vcpu) ||
 	    !(vcpu->kvm->arch.xen_hvm_config.flags & KVM_XEN_HVM_CONFIG_EVTCHN_SEND))
 		return false;
 
 	idx = srcu_read_lock(&vcpu->kvm->srcu);
 	gpa = kvm_mmu_gva_to_gpa_system(vcpu, param, NULL);
 	srcu_read_unlock(&vcpu->kvm->srcu, idx);
-
-	if (!gpa || kvm_vcpu_read_guest(vcpu, gpa, &sched_poll,
-					sizeof(sched_poll))) {
+	if (!gpa) {
 		*r = -EFAULT;
 		return true;
 	}
 
+	if (IS_ENABLED(CONFIG_64BIT) && !longmode) {
+		struct compat_sched_poll sp32;
+
+		/* Sanity check that the compat struct definition is correct */
+		BUILD_BUG_ON(sizeof(sp32) != 16);
+
+		if (kvm_vcpu_read_guest(vcpu, gpa, &sp32, sizeof(sp32))) {
+			*r = -EFAULT;
+			return true;
+		}
+
+		/*
+		 * This is a 32-bit pointer to an array of evtchn_port_t which
+		 * are uint32_t, so once it's converted no further compat
+		 * handling is needed.
+		 */
+		sched_poll.ports = (void *)(unsigned long)(sp32.ports);
+		sched_poll.nr_ports = sp32.nr_ports;
+		sched_poll.timeout = sp32.timeout;
+	} else {
+		if (kvm_vcpu_read_guest(vcpu, gpa, &sched_poll,
+					sizeof(sched_poll))) {
+			*r = -EFAULT;
+			return true;
+		}
+	}
+
 	if (unlikely(sched_poll.nr_ports > 1)) {
 		/* Xen (unofficially) limits number of pollers to 128 */
 		if (sched_poll.nr_ports > 128) {
diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h
index 8503d2c6891e3..ea33d80a0c51f 100644
--- a/arch/x86/kvm/xen.h
+++ b/arch/x86/kvm/xen.h
@@ -207,4 +207,11 @@ struct compat_vcpu_runstate_info {
     uint64_t time[4];
 } __attribute__((packed));
 
+struct compat_sched_poll {
+	/* This is actually a guest virtual address which points to ports. */
+	uint32_t ports;
+	unsigned int nr_ports;
+	uint64_t timeout;
+};
+
 #endif /* __ARCH_X86_KVM_XEN_H__ */

From 8c82a0b3ba1a411b84af5d43a4cc5994efa897ec Mon Sep 17 00:00:00 2001
From: Michal Luczaj <mhal@rbox.co>
Date: Thu, 13 Oct 2022 21:12:24 +0000
Subject: [PATCH 2/9] KVM: Store immutable gfn_to_pfn_cache properties

Move the assignment of immutable properties @kvm, @vcpu, and @usage to
the initializer.  Make _activate() and _deactivate() use stored values.

Note, @len is also effectively immutable for most cases, but not in the
case of the Xen runstate cache, which may be split across two pages and
the length of the first segment will depend on its address.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
[sean: handle @len in a separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>
[dwmw2: acknowledge that @len can actually change for some use cases]
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 arch/x86/kvm/x86.c        | 14 ++++-----
 arch/x86/kvm/xen.c        | 65 ++++++++++++++++++---------------------
 include/linux/kvm_host.h  | 37 +++++++++++-----------
 include/linux/kvm_types.h |  1 +
 virt/kvm/pfncache.c       | 22 ++++++++-----
 5 files changed, 69 insertions(+), 70 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7f850dfb40861..b5e7aea221106 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2317,13 +2317,11 @@ static void kvm_write_system_time(struct kvm_vcpu *vcpu, gpa_t system_time,
 	kvm_make_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu);
 
 	/* we verify if the enable bit is set... */
-	if (system_time & 1) {
-		kvm_gpc_activate(vcpu->kvm, &vcpu->arch.pv_time, vcpu,
-				 KVM_HOST_USES_PFN, system_time & ~1ULL,
+	if (system_time & 1)
+		kvm_gpc_activate(&vcpu->arch.pv_time, system_time & ~1ULL,
 				 sizeof(struct pvclock_vcpu_time_info));
-	} else {
-		kvm_gpc_deactivate(vcpu->kvm, &vcpu->arch.pv_time);
-	}
+	else
+		kvm_gpc_deactivate(&vcpu->arch.pv_time);
 
 	return;
 }
@@ -3391,7 +3389,7 @@ static int kvm_pv_enable_async_pf_int(struct kvm_vcpu *vcpu, u64 data)
 
 static void kvmclock_reset(struct kvm_vcpu *vcpu)
 {
-	kvm_gpc_deactivate(vcpu->kvm, &vcpu->arch.pv_time);
+	kvm_gpc_deactivate(&vcpu->arch.pv_time);
 	vcpu->arch.time = 0;
 }
 
@@ -11542,7 +11540,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 	vcpu->arch.regs_avail = ~0;
 	vcpu->arch.regs_dirty = ~0;
 
-	kvm_gpc_init(&vcpu->arch.pv_time);
+	kvm_gpc_init(&vcpu->arch.pv_time, vcpu->kvm, vcpu, KVM_HOST_USES_PFN);
 
 	if (!irqchip_in_kernel(vcpu->kvm) || kvm_vcpu_is_reset_bsp(vcpu))
 		vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 3e434dc339fb5..55257c2a1610f 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -42,13 +42,12 @@ static int kvm_xen_shared_info_init(struct kvm *kvm, gfn_t gfn)
 	int idx = srcu_read_lock(&kvm->srcu);
 
 	if (gfn == GPA_INVALID) {
-		kvm_gpc_deactivate(kvm, gpc);
+		kvm_gpc_deactivate(gpc);
 		goto out;
 	}
 
 	do {
-		ret = kvm_gpc_activate(kvm, gpc, NULL, KVM_HOST_USES_PFN, gpa,
-				       PAGE_SIZE);
+		ret = kvm_gpc_activate(gpc, gpa, PAGE_SIZE);
 		if (ret)
 			goto out;
 
@@ -323,8 +322,8 @@ static void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, bool atomic)
 			 * to the second page now because the guest changed to
 			 * 64-bit mode, the second GPC won't have been set up.
 			 */
-			if (kvm_gpc_activate(v->kvm, gpc2, NULL, KVM_HOST_USES_PFN,
-					     gpc1->gpa + user_len1, user_len2))
+			if (kvm_gpc_activate(gpc2, gpc1->gpa + user_len1,
+					     user_len2))
 				return;
 
 			/*
@@ -711,15 +710,13 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 			     offsetof(struct compat_vcpu_info, time));
 
 		if (data->u.gpa == GPA_INVALID) {
-			kvm_gpc_deactivate(vcpu->kvm, &vcpu->arch.xen.vcpu_info_cache);
+			kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
 			r = 0;
 			break;
 		}
 
-		r = kvm_gpc_activate(vcpu->kvm,
-				     &vcpu->arch.xen.vcpu_info_cache, NULL,
-				     KVM_HOST_USES_PFN, data->u.gpa,
-				     sizeof(struct vcpu_info));
+		r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_info_cache,
+				     data->u.gpa, sizeof(struct vcpu_info));
 		if (!r)
 			kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
 
@@ -727,15 +724,13 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 
 	case KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO:
 		if (data->u.gpa == GPA_INVALID) {
-			kvm_gpc_deactivate(vcpu->kvm,
-					   &vcpu->arch.xen.vcpu_time_info_cache);
+			kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_time_info_cache);
 			r = 0;
 			break;
 		}
 
-		r = kvm_gpc_activate(vcpu->kvm,
-				     &vcpu->arch.xen.vcpu_time_info_cache,
-				     NULL, KVM_HOST_USES_PFN, data->u.gpa,
+		r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_time_info_cache,
+				     data->u.gpa,
 				     sizeof(struct pvclock_vcpu_time_info));
 		if (!r)
 			kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
@@ -751,10 +746,8 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 		if (data->u.gpa == GPA_INVALID) {
 			r = 0;
 		deactivate_out:
-			kvm_gpc_deactivate(vcpu->kvm,
-					   &vcpu->arch.xen.runstate_cache);
-			kvm_gpc_deactivate(vcpu->kvm,
-					   &vcpu->arch.xen.runstate2_cache);
+			kvm_gpc_deactivate(&vcpu->arch.xen.runstate_cache);
+			kvm_gpc_deactivate(&vcpu->arch.xen.runstate2_cache);
 			break;
 		}
 
@@ -770,20 +763,18 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 
 		/* How much fits in the (first) page? */
 		sz1 = PAGE_SIZE - (data->u.gpa & ~PAGE_MASK);
-		r = kvm_gpc_activate(vcpu->kvm, &vcpu->arch.xen.runstate_cache,
-				     NULL, KVM_HOST_USES_PFN, data->u.gpa, sz1);
+		r = kvm_gpc_activate(&vcpu->arch.xen.runstate_cache,
+				     data->u.gpa, sz1);
 		if (r)
 			goto deactivate_out;
 
 		/* Either map the second page, or deactivate the second GPC */
 		if (sz1 >= sz) {
-			kvm_gpc_deactivate(vcpu->kvm,
-					   &vcpu->arch.xen.runstate2_cache);
+			kvm_gpc_deactivate(&vcpu->arch.xen.runstate2_cache);
 		} else {
 			sz2 = sz - sz1;
 			BUG_ON((data->u.gpa + sz1) & ~PAGE_MASK);
-			r = kvm_gpc_activate(vcpu->kvm, &vcpu->arch.xen.runstate2_cache,
-					     NULL, KVM_HOST_USES_PFN,
+			r = kvm_gpc_activate(&vcpu->arch.xen.runstate2_cache,
 					     data->u.gpa + sz1, sz2);
 			if (r)
 				goto deactivate_out;
@@ -2051,10 +2042,14 @@ void kvm_xen_init_vcpu(struct kvm_vcpu *vcpu)
 
 	timer_setup(&vcpu->arch.xen.poll_timer, cancel_evtchn_poll, 0);
 
-	kvm_gpc_init(&vcpu->arch.xen.runstate_cache);
-	kvm_gpc_init(&vcpu->arch.xen.runstate2_cache);
-	kvm_gpc_init(&vcpu->arch.xen.vcpu_info_cache);
-	kvm_gpc_init(&vcpu->arch.xen.vcpu_time_info_cache);
+	kvm_gpc_init(&vcpu->arch.xen.runstate_cache, vcpu->kvm, NULL,
+		     KVM_HOST_USES_PFN);
+	kvm_gpc_init(&vcpu->arch.xen.runstate2_cache, vcpu->kvm, NULL,
+		     KVM_HOST_USES_PFN);
+	kvm_gpc_init(&vcpu->arch.xen.vcpu_info_cache, vcpu->kvm, NULL,
+		     KVM_HOST_USES_PFN);
+	kvm_gpc_init(&vcpu->arch.xen.vcpu_time_info_cache, vcpu->kvm, NULL,
+		     KVM_HOST_USES_PFN);
 }
 
 void kvm_xen_destroy_vcpu(struct kvm_vcpu *vcpu)
@@ -2062,10 +2057,10 @@ void kvm_xen_destroy_vcpu(struct kvm_vcpu *vcpu)
 	if (kvm_xen_timer_enabled(vcpu))
 		kvm_xen_stop_timer(vcpu);
 
-	kvm_gpc_deactivate(vcpu->kvm, &vcpu->arch.xen.runstate_cache);
-	kvm_gpc_deactivate(vcpu->kvm, &vcpu->arch.xen.runstate2_cache);
-	kvm_gpc_deactivate(vcpu->kvm, &vcpu->arch.xen.vcpu_info_cache);
-	kvm_gpc_deactivate(vcpu->kvm, &vcpu->arch.xen.vcpu_time_info_cache);
+	kvm_gpc_deactivate(&vcpu->arch.xen.runstate_cache);
+	kvm_gpc_deactivate(&vcpu->arch.xen.runstate2_cache);
+	kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
+	kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_time_info_cache);
 
 	del_timer_sync(&vcpu->arch.xen.poll_timer);
 }
@@ -2073,7 +2068,7 @@ void kvm_xen_destroy_vcpu(struct kvm_vcpu *vcpu)
 void kvm_xen_init_vm(struct kvm *kvm)
 {
 	idr_init(&kvm->arch.xen.evtchn_ports);
-	kvm_gpc_init(&kvm->arch.xen.shinfo_cache);
+	kvm_gpc_init(&kvm->arch.xen.shinfo_cache, kvm, NULL, KVM_HOST_USES_PFN);
 }
 
 void kvm_xen_destroy_vm(struct kvm *kvm)
@@ -2081,7 +2076,7 @@ void kvm_xen_destroy_vm(struct kvm *kvm)
 	struct evtchnfd *evtchnfd;
 	int i;
 
-	kvm_gpc_deactivate(kvm, &kvm->arch.xen.shinfo_cache);
+	kvm_gpc_deactivate(&kvm->arch.xen.shinfo_cache);
 
 	idr_for_each_entry(&kvm->arch.xen.evtchn_ports, evtchnfd, i) {
 		if (!evtchnfd->deliver.port.port)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 8f874a9643139..73ded328f9dce 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1260,18 +1260,7 @@ void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn);
  * kvm_gpc_init - initialize gfn_to_pfn_cache.
  *
  * @gpc:	   struct gfn_to_pfn_cache object.
- *
- * This sets up a gfn_to_pfn_cache by initializing locks.  Note, the cache must
- * be zero-allocated (or zeroed by the caller before init).
- */
-void kvm_gpc_init(struct gfn_to_pfn_cache *gpc);
-
-/**
- * kvm_gpc_activate - prepare a cached kernel mapping and HPA for a given guest
- *                    physical address.
- *
  * @kvm:	   pointer to kvm instance.
- * @gpc:	   struct gfn_to_pfn_cache object.
  * @vcpu:	   vCPU to be used for marking pages dirty and to be woken on
  *		   invalidation.
  * @usage:	   indicates if the resulting host physical PFN is used while
@@ -1280,20 +1269,31 @@ void kvm_gpc_init(struct gfn_to_pfn_cache *gpc);
  *		   changes!---will also force @vcpu to exit the guest and
  *		   refresh the cache); and/or if the PFN used directly
  *		   by KVM (and thus needs a kernel virtual mapping).
+ *
+ * This sets up a gfn_to_pfn_cache by initializing locks and assigning the
+ * immutable attributes.  Note, the cache must be zero-allocated (or zeroed by
+ * the caller before init).
+ */
+void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm,
+		  struct kvm_vcpu *vcpu, enum pfn_cache_usage usage);
+
+/**
+ * kvm_gpc_activate - prepare a cached kernel mapping and HPA for a given guest
+ *                    physical address.
+ *
+ * @gpc:	   struct gfn_to_pfn_cache object.
  * @gpa:	   guest physical address to map.
  * @len:	   sanity check; the range being access must fit a single page.
  *
  * @return:	   0 for success.
  *		   -EINVAL for a mapping which would cross a page boundary.
- *                 -EFAULT for an untranslatable guest physical address.
+ *		   -EFAULT for an untranslatable guest physical address.
  *
- * This primes a gfn_to_pfn_cache and links it into the @kvm's list for
+ * This primes a gfn_to_pfn_cache and links it into the @gpc->kvm's list for
  * invalidations to be processed.  Callers are required to use kvm_gpc_check()
  * to ensure that the cache is valid before accessing the target page.
  */
-int kvm_gpc_activate(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
-		     struct kvm_vcpu *vcpu, enum pfn_cache_usage usage,
-		     gpa_t gpa, unsigned long len);
+int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len);
 
 /**
  * kvm_gpc_check - check validity of a gfn_to_pfn_cache.
@@ -1352,13 +1352,12 @@ void kvm_gpc_unmap(struct kvm *kvm, struct gfn_to_pfn_cache *gpc);
 /**
  * kvm_gpc_deactivate - deactivate and unlink a gfn_to_pfn_cache.
  *
- * @kvm:	   pointer to kvm instance.
  * @gpc:	   struct gfn_to_pfn_cache object.
  *
- * This removes a cache from the @kvm's list to be processed on MMU notifier
+ * This removes a cache from the VM's list to be processed on MMU notifier
  * invocation.
  */
-void kvm_gpc_deactivate(struct kvm *kvm, struct gfn_to_pfn_cache *gpc);
+void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
 
 void kvm_sigset_activate(struct kvm_vcpu *vcpu);
 void kvm_sigset_deactivate(struct kvm_vcpu *vcpu);
diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
index 3ca3db020e0e3..76de36e56cdfe 100644
--- a/include/linux/kvm_types.h
+++ b/include/linux/kvm_types.h
@@ -67,6 +67,7 @@ struct gfn_to_pfn_cache {
 	gpa_t gpa;
 	unsigned long uhva;
 	struct kvm_memory_slot *memslot;
+	struct kvm *kvm;
 	struct kvm_vcpu *vcpu;
 	struct list_head list;
 	rwlock_t lock;
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index b4295474519f8..d8ce30b893d97 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -362,25 +362,29 @@ void kvm_gpc_unmap(struct kvm *kvm, struct gfn_to_pfn_cache *gpc)
 }
 EXPORT_SYMBOL_GPL(kvm_gpc_unmap);
 
-void kvm_gpc_init(struct gfn_to_pfn_cache *gpc)
+void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm,
+		  struct kvm_vcpu *vcpu, enum pfn_cache_usage usage)
 {
+	WARN_ON_ONCE(!usage || (usage & KVM_GUEST_AND_HOST_USE_PFN) != usage);
+	WARN_ON_ONCE((usage & KVM_GUEST_USES_PFN) && !vcpu);
+
 	rwlock_init(&gpc->lock);
 	mutex_init(&gpc->refresh_lock);
+
+	gpc->kvm = kvm;
+	gpc->vcpu = vcpu;
+	gpc->usage = usage;
 }
 EXPORT_SYMBOL_GPL(kvm_gpc_init);
 
-int kvm_gpc_activate(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
-		     struct kvm_vcpu *vcpu, enum pfn_cache_usage usage,
-		     gpa_t gpa, unsigned long len)
+int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
 {
-	WARN_ON_ONCE(!usage || (usage & KVM_GUEST_AND_HOST_USE_PFN) != usage);
+	struct kvm *kvm = gpc->kvm;
 
 	if (!gpc->active) {
 		gpc->khva = NULL;
 		gpc->pfn = KVM_PFN_ERR_FAULT;
 		gpc->uhva = KVM_HVA_ERR_BAD;
-		gpc->vcpu = vcpu;
-		gpc->usage = usage;
 		gpc->valid = false;
 
 		spin_lock(&kvm->gpc_lock);
@@ -400,8 +404,10 @@ int kvm_gpc_activate(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
 }
 EXPORT_SYMBOL_GPL(kvm_gpc_activate);
 
-void kvm_gpc_deactivate(struct kvm *kvm, struct gfn_to_pfn_cache *gpc)
+void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc)
 {
+	struct kvm *kvm = gpc->kvm;
+
 	if (gpc->active) {
 		/*
 		 * Deactivate the cache before removing it from the list, KVM

From e308c24a358d1e79951b16c387cbc6c6593639a5 Mon Sep 17 00:00:00 2001
From: Michal Luczaj <mhal@rbox.co>
Date: Thu, 13 Oct 2022 21:12:26 +0000
Subject: [PATCH 3/9] KVM: Use gfn_to_pfn_cache's immutable "kvm" in
 kvm_gpc_check()

Make kvm_gpc_check() use kvm instance cached in gfn_to_pfn_cache.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 arch/x86/kvm/x86.c       |  2 +-
 arch/x86/kvm/xen.c       | 16 +++++++---------
 include/linux/kvm_host.h |  4 +---
 virt/kvm/pfncache.c      |  5 ++---
 4 files changed, 11 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b5e7aea221106..441f08c3af960 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3035,7 +3035,7 @@ static void kvm_setup_guest_pvclock(struct kvm_vcpu *v,
 	unsigned long flags;
 
 	read_lock_irqsave(&gpc->lock, flags);
-	while (!kvm_gpc_check(v->kvm, gpc, gpc->gpa,
+	while (!kvm_gpc_check(gpc, gpc->gpa,
 			      offset + sizeof(*guest_hv_clock))) {
 		read_unlock_irqrestore(&gpc->lock, flags);
 
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 55257c2a1610f..148319e980c41 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -272,7 +272,7 @@ static void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, bool atomic)
 	 * gfn_to_pfn caches that cover the region.
 	 */
 	read_lock_irqsave(&gpc1->lock, flags);
-	while (!kvm_gpc_check(v->kvm, gpc1, gpc1->gpa, user_len1)) {
+	while (!kvm_gpc_check(gpc1, gpc1->gpa, user_len1)) {
 		read_unlock_irqrestore(&gpc1->lock, flags);
 
 		/* When invoked from kvm_sched_out() we cannot sleep */
@@ -308,7 +308,7 @@ static void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, bool atomic)
 		 */
 		read_lock(&gpc2->lock);
 
-		if (!kvm_gpc_check(v->kvm, gpc2, gpc2->gpa, user_len2)) {
+		if (!kvm_gpc_check(gpc2, gpc2->gpa, user_len2)) {
 			read_unlock(&gpc2->lock);
 			read_unlock_irqrestore(&gpc1->lock, flags);
 
@@ -488,8 +488,7 @@ void kvm_xen_inject_pending_events(struct kvm_vcpu *v)
 	 * little more honest about it.
 	 */
 	read_lock_irqsave(&gpc->lock, flags);
-	while (!kvm_gpc_check(v->kvm, gpc, gpc->gpa,
-			      sizeof(struct vcpu_info))) {
+	while (!kvm_gpc_check(gpc, gpc->gpa, sizeof(struct vcpu_info))) {
 		read_unlock_irqrestore(&gpc->lock, flags);
 
 		if (kvm_gpc_refresh(v->kvm, gpc, gpc->gpa,
@@ -553,8 +552,7 @@ int __kvm_xen_has_interrupt(struct kvm_vcpu *v)
 		     sizeof_field(struct compat_vcpu_info, evtchn_upcall_pending));
 
 	read_lock_irqsave(&gpc->lock, flags);
-	while (!kvm_gpc_check(v->kvm, gpc, gpc->gpa,
-			      sizeof(struct vcpu_info))) {
+	while (!kvm_gpc_check(gpc, gpc->gpa, sizeof(struct vcpu_info))) {
 		read_unlock_irqrestore(&gpc->lock, flags);
 
 		/*
@@ -1158,7 +1156,7 @@ static bool wait_pending_event(struct kvm_vcpu *vcpu, int nr_ports,
 
 	read_lock_irqsave(&gpc->lock, flags);
 	idx = srcu_read_lock(&kvm->srcu);
-	if (!kvm_gpc_check(kvm, gpc, gpc->gpa, PAGE_SIZE))
+	if (!kvm_gpc_check(gpc, gpc->gpa, PAGE_SIZE))
 		goto out_rcu;
 
 	ret = false;
@@ -1580,7 +1578,7 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm)
 	idx = srcu_read_lock(&kvm->srcu);
 
 	read_lock_irqsave(&gpc->lock, flags);
-	if (!kvm_gpc_check(kvm, gpc, gpc->gpa, PAGE_SIZE))
+	if (!kvm_gpc_check(gpc, gpc->gpa, PAGE_SIZE))
 		goto out_rcu;
 
 	if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
@@ -1614,7 +1612,7 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm)
 		gpc = &vcpu->arch.xen.vcpu_info_cache;
 
 		read_lock_irqsave(&gpc->lock, flags);
-		if (!kvm_gpc_check(kvm, gpc, gpc->gpa, sizeof(struct vcpu_info))) {
+		if (!kvm_gpc_check(gpc, gpc->gpa, sizeof(struct vcpu_info))) {
 			/*
 			 * Could not access the vcpu_info. Set the bit in-kernel
 			 * and prod the vCPU to deliver it for itself.
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 73ded328f9dce..befc8114ed0da 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1298,7 +1298,6 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
 /**
  * kvm_gpc_check - check validity of a gfn_to_pfn_cache.
  *
- * @kvm:	   pointer to kvm instance.
  * @gpc:	   struct gfn_to_pfn_cache object.
  * @gpa:	   current guest physical address to map.
  * @len:	   sanity check; the range being access must fit a single page.
@@ -1313,8 +1312,7 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
  * Callers in IN_GUEST_MODE may do so without locking, although they should
  * still hold a read lock on kvm->scru for the memslot checks.
  */
-bool kvm_gpc_check(struct kvm *kvm, struct gfn_to_pfn_cache *gpc, gpa_t gpa,
-		   unsigned long len);
+bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len);
 
 /**
  * kvm_gpc_refresh - update a previously initialized cache.
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index d8ce30b893d97..decf4fdde668f 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -76,10 +76,9 @@ void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, unsigned long start,
 	}
 }
 
-bool kvm_gpc_check(struct kvm *kvm, struct gfn_to_pfn_cache *gpc, gpa_t gpa,
-		   unsigned long len)
+bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
 {
-	struct kvm_memslots *slots = kvm_memslots(kvm);
+	struct kvm_memslots *slots = kvm_memslots(gpc->kvm);
 
 	if (!gpc->active)
 		return false;

From 2a0b128a906ab28b1ab41ceedcaf462b6f74f1aa Mon Sep 17 00:00:00 2001
From: Michal Luczaj <mhal@rbox.co>
Date: Thu, 13 Oct 2022 21:12:27 +0000
Subject: [PATCH 4/9] KVM: Clean up hva_to_pfn_retry()

Make hva_to_pfn_retry() use kvm instance cached in gfn_to_pfn_cache.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 virt/kvm/pfncache.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index decf4fdde668f..9d506de6c150d 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -138,7 +138,7 @@ static inline bool mmu_notifier_retry_cache(struct kvm *kvm, unsigned long mmu_s
 	return kvm->mmu_invalidate_seq != mmu_seq;
 }
 
-static kvm_pfn_t hva_to_pfn_retry(struct kvm *kvm, struct gfn_to_pfn_cache *gpc)
+static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
 {
 	/* Note, the new page offset may be different than the old! */
 	void *old_khva = gpc->khva - offset_in_page(gpc->khva);
@@ -158,7 +158,7 @@ static kvm_pfn_t hva_to_pfn_retry(struct kvm *kvm, struct gfn_to_pfn_cache *gpc)
 	gpc->valid = false;
 
 	do {
-		mmu_seq = kvm->mmu_invalidate_seq;
+		mmu_seq = gpc->kvm->mmu_invalidate_seq;
 		smp_rmb();
 
 		write_unlock_irq(&gpc->lock);
@@ -216,7 +216,7 @@ static kvm_pfn_t hva_to_pfn_retry(struct kvm *kvm, struct gfn_to_pfn_cache *gpc)
 		 * attempting to refresh.
 		 */
 		WARN_ON_ONCE(gpc->valid);
-	} while (mmu_notifier_retry_cache(kvm, mmu_seq));
+	} while (mmu_notifier_retry_cache(gpc->kvm, mmu_seq));
 
 	gpc->valid = true;
 	gpc->pfn = new_pfn;
@@ -294,7 +294,7 @@ int kvm_gpc_refresh(struct kvm *kvm, struct gfn_to_pfn_cache *gpc, gpa_t gpa,
 	 * drop the lock and do the HVA to PFN lookup again.
 	 */
 	if (!gpc->valid || old_uhva != gpc->uhva) {
-		ret = hva_to_pfn_retry(kvm, gpc);
+		ret = hva_to_pfn_retry(gpc);
 	} else {
 		/*
 		 * If the HVA→PFN mapping was already valid, don't unmap it.

From 0318f207d1c2e297d1ec1c6e145bb8bd053236f9 Mon Sep 17 00:00:00 2001
From: Michal Luczaj <mhal@rbox.co>
Date: Thu, 13 Oct 2022 21:12:28 +0000
Subject: [PATCH 5/9] KVM: Use gfn_to_pfn_cache's immutable "kvm" in
 kvm_gpc_refresh()

Make kvm_gpc_refresh() use kvm instance cached in gfn_to_pfn_cache.

No functional change intended.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
[sean: leave kvm_gpc_unmap() as-is]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 arch/x86/kvm/x86.c       |  2 +-
 arch/x86/kvm/xen.c       | 10 ++++------
 include/linux/kvm_host.h | 10 ++++------
 virt/kvm/pfncache.c      |  7 +++----
 4 files changed, 12 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 441f08c3af960..490df3e997fac 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3039,7 +3039,7 @@ static void kvm_setup_guest_pvclock(struct kvm_vcpu *v,
 			      offset + sizeof(*guest_hv_clock))) {
 		read_unlock_irqrestore(&gpc->lock, flags);
 
-		if (kvm_gpc_refresh(v->kvm, gpc, gpc->gpa,
+		if (kvm_gpc_refresh(gpc, gpc->gpa,
 				    offset + sizeof(*guest_hv_clock)))
 			return;
 
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 148319e980c41..f50c88b1eaab3 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -279,7 +279,7 @@ static void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, bool atomic)
 		if (atomic)
 			return;
 
-		if (kvm_gpc_refresh(v->kvm, gpc1, gpc1->gpa, user_len1))
+		if (kvm_gpc_refresh(gpc1, gpc1->gpa, user_len1))
 			return;
 
 		read_lock_irqsave(&gpc1->lock, flags);
@@ -491,8 +491,7 @@ void kvm_xen_inject_pending_events(struct kvm_vcpu *v)
 	while (!kvm_gpc_check(gpc, gpc->gpa, sizeof(struct vcpu_info))) {
 		read_unlock_irqrestore(&gpc->lock, flags);
 
-		if (kvm_gpc_refresh(v->kvm, gpc, gpc->gpa,
-				    sizeof(struct vcpu_info)))
+		if (kvm_gpc_refresh(gpc, gpc->gpa, sizeof(struct vcpu_info)))
 			return;
 
 		read_lock_irqsave(&gpc->lock, flags);
@@ -566,8 +565,7 @@ int __kvm_xen_has_interrupt(struct kvm_vcpu *v)
 		if (in_atomic() || !task_is_running(current))
 			return 1;
 
-		if (kvm_gpc_refresh(v->kvm, gpc, gpc->gpa,
-				    sizeof(struct vcpu_info))) {
+		if (kvm_gpc_refresh(gpc, gpc->gpa, sizeof(struct vcpu_info))) {
 			/*
 			 * If this failed, userspace has screwed up the
 			 * vcpu_info mapping. No interrupts for you.
@@ -1710,7 +1708,7 @@ static int kvm_xen_set_evtchn(struct kvm_xen_evtchn *xe, struct kvm *kvm)
 			break;
 
 		idx = srcu_read_lock(&kvm->srcu);
-		rc = kvm_gpc_refresh(kvm, gpc, gpc->gpa, PAGE_SIZE);
+		rc = kvm_gpc_refresh(gpc, gpc->gpa, PAGE_SIZE);
 		srcu_read_unlock(&kvm->srcu, idx);
 	} while(!rc);
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index befc8114ed0da..3ce4650776b87 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1317,23 +1317,21 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len);
 /**
  * kvm_gpc_refresh - update a previously initialized cache.
  *
- * @kvm:	   pointer to kvm instance.
  * @gpc:	   struct gfn_to_pfn_cache object.
  * @gpa:	   updated guest physical address to map.
  * @len:	   sanity check; the range being access must fit a single page.
- *
+
  * @return:	   0 for success.
  *		   -EINVAL for a mapping which would cross a page boundary.
- *                 -EFAULT for an untranslatable guest physical address.
+ *		   -EFAULT for an untranslatable guest physical address.
  *
  * This will attempt to refresh a gfn_to_pfn_cache. Note that a successful
- * returm from this function does not mean the page can be immediately
+ * return from this function does not mean the page can be immediately
  * accessed because it may have raced with an invalidation. Callers must
  * still lock and check the cache status, as this function does not return
  * with the lock still held to permit access.
  */
-int kvm_gpc_refresh(struct kvm *kvm, struct gfn_to_pfn_cache *gpc, gpa_t gpa,
-		    unsigned long len);
+int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len);
 
 /**
  * kvm_gpc_unmap - temporarily unmap a gfn_to_pfn_cache.
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 9d506de6c150d..015c5d16948a1 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -237,10 +237,9 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
 	return -EFAULT;
 }
 
-int kvm_gpc_refresh(struct kvm *kvm, struct gfn_to_pfn_cache *gpc, gpa_t gpa,
-		    unsigned long len)
+int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
 {
-	struct kvm_memslots *slots = kvm_memslots(kvm);
+	struct kvm_memslots *slots = kvm_memslots(gpc->kvm);
 	unsigned long page_offset = gpa & ~PAGE_MASK;
 	bool unmap_old = false;
 	unsigned long old_uhva;
@@ -399,7 +398,7 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
 		gpc->active = true;
 		write_unlock_irq(&gpc->lock);
 	}
-	return kvm_gpc_refresh(kvm, gpc, gpa, len);
+	return kvm_gpc_refresh(gpc, gpa, len);
 }
 EXPORT_SYMBOL_GPL(kvm_gpc_activate);
 

From 9f87791d686d85614584438d4f249eb32ef7964c Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Thu, 13 Oct 2022 21:12:29 +0000
Subject: [PATCH 6/9] KVM: Drop KVM's API to allow temporarily unmapping
 gfn=>pfn cache

Drop kvm_gpc_unmap() as it has no users and unclear requirements.  The
API was added as part of the original gfn_to_pfn_cache support, but its
sole usage[*] was never merged.  Fold the guts of kvm_gpc_unmap() into
the deactivate path and drop the API.  Omit acquiring refresh_lock as
as concurrent calls to kvm_gpc_deactivate() are not allowed (this is
not enforced, e.g. via lockdep. due to it being called during vCPU
destruction).

If/when temporary unmapping makes a comeback, the desirable behavior is
likely to restrict temporary unmapping to vCPU-exclusive mappings and
require the vcpu->mutex be held to serialize unmap.  Use of the
refresh_lock to protect unmapping was somewhat specuatively added by
commit 93984f19e7bc ("KVM: Fully serialize gfn=>pfn cache refresh via
mutex") to guard against concurrent unmaps, but the primary use case of
the temporary unmap, nested virtualization[*], doesn't actually need or
want concurrent unmaps.

[*] https://lore.kernel.org/all/20211210163625.2886-7-dwmw2@infradead.org

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 include/linux/kvm_host.h | 12 -----------
 virt/kvm/pfncache.c      | 44 +++++++++++++++-------------------------
 2 files changed, 16 insertions(+), 40 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3ce4650776b87..eac76965cf448 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1333,18 +1333,6 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len);
  */
 int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len);
 
-/**
- * kvm_gpc_unmap - temporarily unmap a gfn_to_pfn_cache.
- *
- * @kvm:	   pointer to kvm instance.
- * @gpc:	   struct gfn_to_pfn_cache object.
- *
- * This unmaps the referenced page. The cache is left in the invalid state
- * but at least the mapping from GPA to userspace HVA will remain cached
- * and can be reused on a subsequent refresh.
- */
-void kvm_gpc_unmap(struct kvm *kvm, struct gfn_to_pfn_cache *gpc);
-
 /**
  * kvm_gpc_deactivate - deactivate and unlink a gfn_to_pfn_cache.
  *
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 015c5d16948a1..5b25127936915 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -333,33 +333,6 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
 }
 EXPORT_SYMBOL_GPL(kvm_gpc_refresh);
 
-void kvm_gpc_unmap(struct kvm *kvm, struct gfn_to_pfn_cache *gpc)
-{
-	void *old_khva;
-	kvm_pfn_t old_pfn;
-
-	mutex_lock(&gpc->refresh_lock);
-	write_lock_irq(&gpc->lock);
-
-	gpc->valid = false;
-
-	old_khva = gpc->khva - offset_in_page(gpc->khva);
-	old_pfn = gpc->pfn;
-
-	/*
-	 * We can leave the GPA → uHVA map cache intact but the PFN
-	 * lookup will need to be redone even for the same page.
-	 */
-	gpc->khva = NULL;
-	gpc->pfn = KVM_PFN_ERR_FAULT;
-
-	write_unlock_irq(&gpc->lock);
-	mutex_unlock(&gpc->refresh_lock);
-
-	gpc_unmap_khva(old_pfn, old_khva);
-}
-EXPORT_SYMBOL_GPL(kvm_gpc_unmap);
-
 void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm,
 		  struct kvm_vcpu *vcpu, enum pfn_cache_usage usage)
 {
@@ -405,6 +378,8 @@ EXPORT_SYMBOL_GPL(kvm_gpc_activate);
 void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc)
 {
 	struct kvm *kvm = gpc->kvm;
+	kvm_pfn_t old_pfn;
+	void *old_khva;
 
 	if (gpc->active) {
 		/*
@@ -414,13 +389,26 @@ void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc)
 		 */
 		write_lock_irq(&gpc->lock);
 		gpc->active = false;
+		gpc->valid = false;
+
+		/*
+		 * Leave the GPA => uHVA cache intact, it's protected by the
+		 * memslot generation.  The PFN lookup needs to be redone every
+		 * time as mmu_notifier protection is lost when the cache is
+		 * removed from the VM's gpc_list.
+		 */
+		old_khva = gpc->khva - offset_in_page(gpc->khva);
+		gpc->khva = NULL;
+
+		old_pfn = gpc->pfn;
+		gpc->pfn = KVM_PFN_ERR_FAULT;
 		write_unlock_irq(&gpc->lock);
 
 		spin_lock(&kvm->gpc_lock);
 		list_del(&gpc->list);
 		spin_unlock(&kvm->gpc_lock);
 
-		kvm_gpc_unmap(kvm, gpc);
+		gpc_unmap_khva(old_pfn, old_khva);
 	}
 }
 EXPORT_SYMBOL_GPL(kvm_gpc_deactivate);

From 5762cb10235776dd1ed5f5f9d6c1aff2b73bec5c Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Thu, 13 Oct 2022 21:12:30 +0000
Subject: [PATCH 7/9] KVM: Do not partially reinitialize gfn=>pfn cache during
 activation

Don't partially reinitialize a gfn=>pfn cache when activating the cache,
and instead assert that the cache is not valid during activation.  Bug
the VM if the assertion fails, as use-after-free and/or data corruption
is all but guaranteed if KVM ends up with a valid-but-inactive cache.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 virt/kvm/pfncache.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 5b25127936915..c1a772cedc4bd 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -345,6 +345,8 @@ void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm,
 	gpc->kvm = kvm;
 	gpc->vcpu = vcpu;
 	gpc->usage = usage;
+	gpc->pfn = KVM_PFN_ERR_FAULT;
+	gpc->uhva = KVM_HVA_ERR_BAD;
 }
 EXPORT_SYMBOL_GPL(kvm_gpc_init);
 
@@ -353,10 +355,8 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
 	struct kvm *kvm = gpc->kvm;
 
 	if (!gpc->active) {
-		gpc->khva = NULL;
-		gpc->pfn = KVM_PFN_ERR_FAULT;
-		gpc->uhva = KVM_HVA_ERR_BAD;
-		gpc->valid = false;
+		if (KVM_BUG_ON(gpc->valid, kvm))
+			return -EIO;
 
 		spin_lock(&kvm->gpc_lock);
 		list_add(&gpc->list, &kvm->gpc_list);

From 58f5ee5fedd981e05cb086cba4e8f923c3727a04 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Thu, 13 Oct 2022 21:12:31 +0000
Subject: [PATCH 8/9] KVM: Drop @gpa from exported gfn=>pfn cache check() and
 refresh() helpers

Drop the @gpa param from the exported check()+refresh() helpers and limit
changing the cache's GPA to the activate path.  All external users just
feed in gpc->gpa, i.e. this is a fancy nop.

Allowing users to change the GPA at check()+refresh() is dangerous as
those helpers explicitly allow concurrent calls, e.g. KVM could get into
a livelock scenario.  It's also unclear as to what the expected behavior
should be if multiple tasks attempt to refresh with different GPAs.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 arch/x86/kvm/x86.c       |  6 ++----
 arch/x86/kvm/xen.c       | 22 +++++++++++-----------
 include/linux/kvm_host.h |  8 +++-----
 virt/kvm/pfncache.c      | 17 +++++++++++------
 4 files changed, 27 insertions(+), 26 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 490df3e997fac..006b445996a9a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3035,12 +3035,10 @@ static void kvm_setup_guest_pvclock(struct kvm_vcpu *v,
 	unsigned long flags;
 
 	read_lock_irqsave(&gpc->lock, flags);
-	while (!kvm_gpc_check(gpc, gpc->gpa,
-			      offset + sizeof(*guest_hv_clock))) {
+	while (!kvm_gpc_check(gpc, offset + sizeof(*guest_hv_clock))) {
 		read_unlock_irqrestore(&gpc->lock, flags);
 
-		if (kvm_gpc_refresh(gpc, gpc->gpa,
-				    offset + sizeof(*guest_hv_clock)))
+		if (kvm_gpc_refresh(gpc, offset + sizeof(*guest_hv_clock)))
 			return;
 
 		read_lock_irqsave(&gpc->lock, flags);
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index f50c88b1eaab3..5208e05ca9a6c 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -272,14 +272,14 @@ static void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, bool atomic)
 	 * gfn_to_pfn caches that cover the region.
 	 */
 	read_lock_irqsave(&gpc1->lock, flags);
-	while (!kvm_gpc_check(gpc1, gpc1->gpa, user_len1)) {
+	while (!kvm_gpc_check(gpc1, user_len1)) {
 		read_unlock_irqrestore(&gpc1->lock, flags);
 
 		/* When invoked from kvm_sched_out() we cannot sleep */
 		if (atomic)
 			return;
 
-		if (kvm_gpc_refresh(gpc1, gpc1->gpa, user_len1))
+		if (kvm_gpc_refresh(gpc1, user_len1))
 			return;
 
 		read_lock_irqsave(&gpc1->lock, flags);
@@ -308,7 +308,7 @@ static void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, bool atomic)
 		 */
 		read_lock(&gpc2->lock);
 
-		if (!kvm_gpc_check(gpc2, gpc2->gpa, user_len2)) {
+		if (!kvm_gpc_check(gpc2, user_len2)) {
 			read_unlock(&gpc2->lock);
 			read_unlock_irqrestore(&gpc1->lock, flags);
 
@@ -488,10 +488,10 @@ void kvm_xen_inject_pending_events(struct kvm_vcpu *v)
 	 * little more honest about it.
 	 */
 	read_lock_irqsave(&gpc->lock, flags);
-	while (!kvm_gpc_check(gpc, gpc->gpa, sizeof(struct vcpu_info))) {
+	while (!kvm_gpc_check(gpc, sizeof(struct vcpu_info))) {
 		read_unlock_irqrestore(&gpc->lock, flags);
 
-		if (kvm_gpc_refresh(gpc, gpc->gpa, sizeof(struct vcpu_info)))
+		if (kvm_gpc_refresh(gpc, sizeof(struct vcpu_info)))
 			return;
 
 		read_lock_irqsave(&gpc->lock, flags);
@@ -551,7 +551,7 @@ int __kvm_xen_has_interrupt(struct kvm_vcpu *v)
 		     sizeof_field(struct compat_vcpu_info, evtchn_upcall_pending));
 
 	read_lock_irqsave(&gpc->lock, flags);
-	while (!kvm_gpc_check(gpc, gpc->gpa, sizeof(struct vcpu_info))) {
+	while (!kvm_gpc_check(gpc, sizeof(struct vcpu_info))) {
 		read_unlock_irqrestore(&gpc->lock, flags);
 
 		/*
@@ -565,7 +565,7 @@ int __kvm_xen_has_interrupt(struct kvm_vcpu *v)
 		if (in_atomic() || !task_is_running(current))
 			return 1;
 
-		if (kvm_gpc_refresh(gpc, gpc->gpa, sizeof(struct vcpu_info))) {
+		if (kvm_gpc_refresh(gpc, sizeof(struct vcpu_info))) {
 			/*
 			 * If this failed, userspace has screwed up the
 			 * vcpu_info mapping. No interrupts for you.
@@ -1154,7 +1154,7 @@ static bool wait_pending_event(struct kvm_vcpu *vcpu, int nr_ports,
 
 	read_lock_irqsave(&gpc->lock, flags);
 	idx = srcu_read_lock(&kvm->srcu);
-	if (!kvm_gpc_check(gpc, gpc->gpa, PAGE_SIZE))
+	if (!kvm_gpc_check(gpc, PAGE_SIZE))
 		goto out_rcu;
 
 	ret = false;
@@ -1576,7 +1576,7 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm)
 	idx = srcu_read_lock(&kvm->srcu);
 
 	read_lock_irqsave(&gpc->lock, flags);
-	if (!kvm_gpc_check(gpc, gpc->gpa, PAGE_SIZE))
+	if (!kvm_gpc_check(gpc, PAGE_SIZE))
 		goto out_rcu;
 
 	if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
@@ -1610,7 +1610,7 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm)
 		gpc = &vcpu->arch.xen.vcpu_info_cache;
 
 		read_lock_irqsave(&gpc->lock, flags);
-		if (!kvm_gpc_check(gpc, gpc->gpa, sizeof(struct vcpu_info))) {
+		if (!kvm_gpc_check(gpc, sizeof(struct vcpu_info))) {
 			/*
 			 * Could not access the vcpu_info. Set the bit in-kernel
 			 * and prod the vCPU to deliver it for itself.
@@ -1708,7 +1708,7 @@ static int kvm_xen_set_evtchn(struct kvm_xen_evtchn *xe, struct kvm *kvm)
 			break;
 
 		idx = srcu_read_lock(&kvm->srcu);
-		rc = kvm_gpc_refresh(gpc, gpc->gpa, PAGE_SIZE);
+		rc = kvm_gpc_refresh(gpc, PAGE_SIZE);
 		srcu_read_unlock(&kvm->srcu, idx);
 	} while(!rc);
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index eac76965cf448..7008846fd3dd2 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1299,7 +1299,6 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
  * kvm_gpc_check - check validity of a gfn_to_pfn_cache.
  *
  * @gpc:	   struct gfn_to_pfn_cache object.
- * @gpa:	   current guest physical address to map.
  * @len:	   sanity check; the range being access must fit a single page.
  *
  * @return:	   %true if the cache is still valid and the address matches.
@@ -1312,15 +1311,14 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
  * Callers in IN_GUEST_MODE may do so without locking, although they should
  * still hold a read lock on kvm->scru for the memslot checks.
  */
-bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len);
+bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len);
 
 /**
  * kvm_gpc_refresh - update a previously initialized cache.
  *
  * @gpc:	   struct gfn_to_pfn_cache object.
- * @gpa:	   updated guest physical address to map.
  * @len:	   sanity check; the range being access must fit a single page.
-
+ *
  * @return:	   0 for success.
  *		   -EINVAL for a mapping which would cross a page boundary.
  *		   -EFAULT for an untranslatable guest physical address.
@@ -1331,7 +1329,7 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len);
  * still lock and check the cache status, as this function does not return
  * with the lock still held to permit access.
  */
-int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len);
+int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len);
 
 /**
  * kvm_gpc_deactivate - deactivate and unlink a gfn_to_pfn_cache.
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index c1a772cedc4bd..a805cc1544bf6 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -76,18 +76,17 @@ void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, unsigned long start,
 	}
 }
 
-bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
+bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len)
 {
 	struct kvm_memslots *slots = kvm_memslots(gpc->kvm);
 
 	if (!gpc->active)
 		return false;
 
-	if ((gpa & ~PAGE_MASK) + len > PAGE_SIZE)
+	if ((gpc->gpa & ~PAGE_MASK) + len > PAGE_SIZE)
 		return false;
 
-	if (gpc->gpa != gpa || gpc->generation != slots->generation ||
-	    kvm_is_error_hva(gpc->uhva))
+	if (gpc->generation != slots->generation || kvm_is_error_hva(gpc->uhva))
 		return false;
 
 	if (!gpc->valid)
@@ -237,7 +236,8 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
 	return -EFAULT;
 }
 
-int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
+static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
+			     unsigned long len)
 {
 	struct kvm_memslots *slots = kvm_memslots(gpc->kvm);
 	unsigned long page_offset = gpa & ~PAGE_MASK;
@@ -331,6 +331,11 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
 
 	return ret;
 }
+
+int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len)
+{
+	return __kvm_gpc_refresh(gpc, gpc->gpa, len);
+}
 EXPORT_SYMBOL_GPL(kvm_gpc_refresh);
 
 void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm,
@@ -371,7 +376,7 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
 		gpc->active = true;
 		write_unlock_irq(&gpc->lock);
 	}
-	return kvm_gpc_refresh(gpc, gpa, len);
+	return __kvm_gpc_refresh(gpc, gpa, len);
 }
 EXPORT_SYMBOL_GPL(kvm_gpc_activate);
 

From 06e155c44aa0e7921aa44d3c67f8ea464b16cb75 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Thu, 13 Oct 2022 21:12:32 +0000
Subject: [PATCH 9/9] KVM: Skip unnecessary "unmap" if gpc is already valid
 during refresh

When refreshing a gfn=>pfn cache, skip straight to unlocking if the cache
already valid instead of stuffing the "old" variables to turn the
unmapping outro into a nop.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 virt/kvm/pfncache.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index a805cc1544bf6..2d6aba6778307 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -301,9 +301,8 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
 		 * may have changed.
 		 */
 		gpc->khva = old_khva + page_offset;
-		old_pfn = KVM_PFN_ERR_FAULT;
-		old_khva = NULL;
 		ret = 0;
+		goto out_unlock;
 	}
 
  out: