@@ -54,7 +54,8 @@
* used in kvm, other bits are visible for userspace which are defined in
* include/uapi/linux/kvm.h.
*/
-#define KVM_MEMSLOT_INVALID (1UL << 16)
+#define KVM_MEMSLOT_INVALID (1UL << 16)
+#define KVM_MEMSLOT_SUPPORTS_GMEM_SHARED (1UL << 17)
/*
* Bit 63 of the memslot generation number is an "update in-progress flag",
@@ -2502,6 +2503,14 @@ static inline void kvm_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_PRIVATE;
}
+static inline bool kvm_gmem_memslot_supports_shared(const struct kvm_memory_slot *slot)
+{
+ if (!IS_ENABLED(CONFIG_KVM_GMEM_SHARED_MEM))
+ return false;
+
+ return slot->flags & KVM_MEMSLOT_SUPPORTS_GMEM_SHARED;
+}
+
#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
static inline unsigned long kvm_get_memory_attributes(struct kvm *kvm, gfn_t gfn)
{
@@ -595,6 +595,8 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot,
*/
WRITE_ONCE(slot->gmem.file, file);
slot->gmem.pgoff = start;
+ if (kvm_gmem_supports_shared(inode))
+ slot->flags |= KVM_MEMSLOT_SUPPORTS_GMEM_SHARED;
xa_store_range(&gmem->bindings, start, end - 1, slot, GFP_KERNEL);
filemap_invalidate_unlock(inode->i_mapping);
Add a new internal flag in the top half of memslot->flags to track when a guest_memfd-backed slot supports shared memory, which is reserved for internal use in KVM. This avoids repeatedly checking the underlying guest_memfd file for shared memory support, which requires taking a reference on the file. Suggested-by: David Hildenbrand <david@redhat.com> Signed-off-by: Fuad Tabba <tabba@google.com> --- include/linux/kvm_host.h | 11 ++++++++++- virt/kvm/guest_memfd.c | 2 ++ 2 files changed, 12 insertions(+), 1 deletion(-)