KVM: MMU: Do not treat ZONE_DEVICE pages as being reserved

[mirror_ubuntu-bionic-kernel.git] / virt / kvm / kvm_main.c

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index c6874c40bfbd027be6cb3eb1fa819edf2c0ee38b..79ed514e32bdf0c9488b4062cd1312946e6c1ecb 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -141,10 +141,30 @@ __weak void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
 {
 }
 
+bool kvm_is_zone_device_pfn(kvm_pfn_t pfn)
+{
+       /*
+        * The metadata used by is_zone_device_page() to determine whether or
+        * not a page is ZONE_DEVICE is guaranteed to be valid if and only if
+        * the device has been pinned, e.g. by get_user_pages().  WARN if the
+        * page_count() is zero to help detect bad usage of this helper.
+        */
+       if (!pfn_valid(pfn) || WARN_ON_ONCE(!page_count(pfn_to_page(pfn))))
+               return false;
+
+       return is_zone_device_page(pfn_to_page(pfn));
+}
+
 bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
 {
+       /*
+        * ZONE_DEVICE pages currently set PG_reserved, but from a refcounting
+        * perspective they are "normal" pages, albeit with slightly different
+        * usage rules.
+        */
        if (pfn_valid(pfn))
-               return PageReserved(pfn_to_page(pfn));
+               return PageReserved(pfn_to_page(pfn)) &&
+                      !kvm_is_zone_device_pfn(pfn);
 
        return true;
 }
@@ -1730,7 +1750,7 @@ EXPORT_SYMBOL_GPL(kvm_release_pfn_dirty);
 
 void kvm_set_pfn_dirty(kvm_pfn_t pfn)
 {
-       if (!kvm_is_reserved_pfn(pfn)) {
+       if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn)) {
                struct page *page = pfn_to_page(pfn);
 
                if (!PageReserved(page))
@@ -1741,7 +1761,7 @@ EXPORT_SYMBOL_GPL(kvm_set_pfn_dirty);
 
 void kvm_set_pfn_accessed(kvm_pfn_t pfn)
 {
-       if (!kvm_is_reserved_pfn(pfn))
+       if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn))
                mark_page_accessed(pfn_to_page(pfn));
 }
 EXPORT_SYMBOL_GPL(kvm_set_pfn_accessed);