kvm: fix potentially corrupt mmio cache

[pandora-kernel.git] / virt / kvm / kvm_main.c

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 7176929..bb8641b 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -95,8 +95,6 @@ static int hardware_enable_all(void);
 static void hardware_disable_all(void);
 
 static void kvm_io_bus_destroy(struct kvm_io_bus *bus);
-static void update_memslots(struct kvm_memslots *slots,
-                           struct kvm_memory_slot *new, u64 last_generation);
 
 static void kvm_release_pfn_dirty(pfn_t pfn);
 static void mark_page_dirty_in_slot(struct kvm *kvm,
@@ -477,6 +475,13 @@ static struct kvm *kvm_create_vm(unsigned long type)
        kvm->memslots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
        if (!kvm->memslots)
                goto out_err_no_srcu;
+
+       /*
+        * Init kvm generation close to the maximum to easily test the
+        * code of handling generation number wrap-around.
+        */
+       kvm->memslots->generation = -150;
+
        kvm_init_memslots_id(kvm);
        if (init_srcu_struct(&kvm->srcu))
                goto out_err_no_srcu;
@@ -688,8 +693,7 @@ static void sort_memslots(struct kvm_memslots *slots)
 }
 
 static void update_memslots(struct kvm_memslots *slots,
-                           struct kvm_memory_slot *new,
-                           u64 last_generation)
+                           struct kvm_memory_slot *new)
 {
        if (new) {
                int id = new->id;
@@ -700,8 +704,6 @@ static void update_memslots(struct kvm_memslots *slots,
                if (new->npages != npages)
                        sort_memslots(slots);
        }
-
-       slots->generation = last_generation + 1;
 }
 
 static int check_memory_region_flags(struct kvm_userspace_memory_region *mem)
@@ -723,10 +725,24 @@ static struct kvm_memslots *install_new_memslots(struct kvm *kvm,
 {
        struct kvm_memslots *old_memslots = kvm->memslots;
 
-       update_memslots(slots, new, kvm->memslots->generation);
+       /*
+        * Set the low bit in the generation, which disables SPTE caching
+        * until the end of synchronize_srcu_expedited.
+        */
+       WARN_ON(old_memslots->generation & 1);
+       slots->generation = old_memslots->generation + 1;
+
+       update_memslots(slots, new);
        rcu_assign_pointer(kvm->memslots, slots);
        synchronize_srcu_expedited(&kvm->srcu);
 
+       /*
+        * Increment the new memslot generation a second time. This prevents
+        * vm exits that race with memslot updates from caching a memslot
+        * generation that will (potentially) be valid forever.
+        */
+       slots->generation++;
+
        kvm_arch_memslots_updated(kvm);
 
        return old_memslots;