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>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 490df3e..006b445 100644 (file)
--- 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 f50c88b..5208e05 100644 (file)
--- 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 eac7696..7008846 100644 (file)
--- 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 c1a772c..a805cc1 100644 (file)
--- 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 @@ out_error:
        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 @@ out_unlock:
 
        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);