@@ -75,4 +75,7 @@ kvm_page_track_unregister_notifier(struct kvm *kvm,
void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
int bytes);
void kvm_page_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot *slot);
+
+bool kvm_page_track_has_external_user(struct kvm *kvm);
+
#endif
@@ -303,3 +303,8 @@ void kvm_page_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot *slot)
n->track_flush_slot(kvm, slot, n);
srcu_read_unlock(&head->track_srcu, idx);
}
+
+bool kvm_page_track_has_external_user(struct kvm *kvm)
+{
+ return hlist_empty(&kvm->arch.track_notifier_head.track_notifier_list);
+}
@@ -12588,6 +12588,13 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
struct kvm_memory_slot *new,
enum kvm_mr_change change)
{
+ /*
+ * KVM doesn't support moving memslots when there are external page
+ * trackers attached to the VM, i.e. if KVMGT is in use.
+ */
+ if (change == KVM_MR_MOVE && kvm_page_track_has_external_user(kvm))
+ return -EINVAL;
+
if (change == KVM_MR_CREATE || change == KVM_MR_MOVE) {
if ((new->base_gfn + new->npages - 1) > kvm_mmu_max_gfn())
return -EINVAL;
Disallow moving memslots if the VM has external page-track users, i.e. if KVMGT is being used to expose a virtual GPU to the guest, as KVMGT doesn't correctly handle moving memory regions. Note, this is potential ABI breakage! E.g. userspace could move regions that aren't shadowed by KVMGT without harming the guest. However, the only known user of KVMGT is QEMU, and QEMU doesn't move generic memory regions. KVM's own support for moving memory regions was also broken for multiple years (albeit for an edge case, but arguably moving RAM is itself an edge case), e.g. see commit edd4fa37baa6 ("KVM: x86: Allocate new rmap and large page tracking when moving memslot"). Reviewed-by: Yan Zhao <yan.y.zhao@intel.com> Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/include/asm/kvm_page_track.h | 3 +++ arch/x86/kvm/mmu/page_track.c | 5 +++++ arch/x86/kvm/x86.c | 7 +++++++ 3 files changed, 15 insertions(+)