[PATCH 13/16] KVM: Drop @gpa from exported gfn=>pfn cache check() and refresh() helpers

[Paolo Bonzini <pbonzini@redhat.com>]

From: Sean Christopherson <seanjc@google.com>

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>
Message-Id: <20221013211234.1318131-14-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/x86.c       |  4 ++--
 arch/x86/kvm/xen.c       | 20 ++++++++++----------
 include/linux/kvm_host.h |  6 ++----
 virt/kvm/pfncache.c      | 11 ++++-------
 4 files changed, 18 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bdc3110650d3..f7ee5ee58990 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3034,10 +3034,10 @@ static void kvm_setup_guest_pvclock(struct kvm_vcpu *v,
 	WARN_ON_ONCE(gpc->len != offset + sizeof(*guest_hv_clock));
 
 	read_lock_irqsave(&gpc->lock, flags);
-	while (!kvm_gpc_check(gpc, gpc->gpa)) {
+	while (!kvm_gpc_check(gpc)) {
 		read_unlock_irqrestore(&gpc->lock, flags);
 
-		if (kvm_gpc_refresh(gpc, gpc->gpa))
+		if (kvm_gpc_refresh(gpc))
 			return;
 
 		read_lock_irqsave(&gpc->lock, flags);
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 545ecbd0ca36..7b7b1eb88a0b 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -241,14 +241,14 @@ void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, int state)
 		return;
 
 	read_lock_irqsave(&gpc->lock, flags);
-	while (!kvm_gpc_check(gpc, gpc->gpa)) {
+	while (!kvm_gpc_check(gpc)) {
 		read_unlock_irqrestore(&gpc->lock, flags);
 
 		/* When invoked from kvm_sched_out() we cannot sleep */
 		if (state == RUNSTATE_runnable)
 			return;
 
-		if (kvm_gpc_refresh(gpc, gpc->gpa))
+		if (kvm_gpc_refresh(gpc))
 			return;
 
 		read_lock_irqsave(&gpc->lock, flags);
@@ -374,10 +374,10 @@ 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)) {
+	while (!kvm_gpc_check(gpc)) {
 		read_unlock_irqrestore(&gpc->lock, flags);
 
-		if (kvm_gpc_refresh(gpc, gpc->gpa))
+		if (kvm_gpc_refresh(gpc))
 			return;
 
 		read_lock_irqsave(&gpc->lock, flags);
@@ -437,7 +437,7 @@ 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)) {
+	while (!kvm_gpc_check(gpc)) {
 		read_unlock_irqrestore(&gpc->lock, flags);
 
 		/*
@@ -451,7 +451,7 @@ 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)) {
+		if (kvm_gpc_refresh(gpc)) {
 			/*
 			 * If this failed, userspace has screwed up the
 			 * vcpu_info mapping. No interrupts for you.
@@ -981,7 +981,7 @@ 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))
+	if (!kvm_gpc_check(gpc))
 		goto out_rcu;
 
 	ret = false;
@@ -1372,7 +1372,7 @@ 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))
+	if (!kvm_gpc_check(gpc))
 		goto out_rcu;
 
 	if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
@@ -1406,7 +1406,7 @@ 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)) {
+		if (!kvm_gpc_check(gpc)) {
 			/*
 			 * Could not access the vcpu_info. Set the bit in-kernel
 			 * and prod the vCPU to deliver it for itself.
@@ -1504,7 +1504,7 @@ 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);
+		rc = kvm_gpc_refresh(gpc);
 		srcu_read_unlock(&kvm->srcu, idx);
 	} while(!rc);
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3847b721e753..fd6b58c870cf 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1282,7 +1282,6 @@ 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.
  *
  * @return:	   %true if the cache is still valid and the address matches.
  *		   %false if the cache is not valid.
@@ -1294,13 +1293,12 @@ 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);
+bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc);
 
 /**
  * kvm_gpc_refresh - update a previously initialized cache.
  *
  * @gpc:	   struct gfn_to_pfn_cache object.
- * @gpa:	   updated guest physical address to map.
  *
  * @return:	   0 for success.
  *		   -EINVAL for a mapping which would cross a page boundary.
@@ -1312,7 +1310,7 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, gpa_t gpa);
  * 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);
+int kvm_gpc_refresh(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 06fcf03c2da6..68e2e53eac8a 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -76,17 +76,14 @@ 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)
+bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc)
 {
 	struct kvm_memslots *slots = kvm_memslots(gpc->kvm);
 
 	if (!gpc->active)
 		return false;
 
-	if ((gpa & ~PAGE_MASK) + gpc->len > PAGE_SIZE)
-		return false;
-
-	if (gpc->gpa != gpa || gpc->generation != slots->generation ||
+	if (gpc->generation != slots->generation ||
 	    kvm_is_error_hva(gpc->uhva))
 		return false;
 
@@ -329,9 +326,9 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned l
 	return ret;
 }
 
-int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa)
+int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc)
 {
-	return __kvm_gpc_refresh(gpc, gpa, gpc->len);
+	return __kvm_gpc_refresh(gpc, gpc->gpa, gpc->len);
 }
 EXPORT_SYMBOL_GPL(kvm_gpc_refresh);
 
-- 
2.31.1