Commit d497a0fa authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: WARN if there are dangling MMU invalidations at VM destruction 

Add an assertion that there are no in-progress MMU invalidations when a
VM is being destroyed, with the exception of the scenario where KVM
unregisters its MMU notifier between an .invalidate_range_start() call and
the corresponding .invalidate_range_end().

KVM can't detect unpaired calls from the mmu_notifier due to the above
exception waiver, but the assertion can detect KVM bugs, e.g. such as the
bug that *almost* escaped initial guest_memfd development.

Link: https://lore.kernel.org/all/e397d30c-c6af-e68f-d18e-b4e3739c5389@linux.intel.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarFuad Tabba <tabba@google.com>
Tested-by: default avatarFuad Tabba <tabba@google.com>
Message-Id: <20231027182217.3615211-5-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 8569992d

virt/kvm/kvm_main.c

+8 −1
Original line number Diff line number Diff line
@@ -1358,9 +1358,16 @@ static void kvm_destroy_vm(struct kvm *kvm) 
	 * No threads can be waiting in kvm_swap_active_memslots() as the

	 * last reference on KVM has been dropped, but freeing

	 * memslots would deadlock without this manual intervention.

	 *

	 * If the count isn't unbalanced, i.e. KVM did NOT unregister its MMU

	 * notifier between a start() and end(), then there shouldn't be any

	 * in-progress invalidations.

	 */

	WARN_ON(rcuwait_active(&kvm->mn_memslots_update_rcuwait));

	if (kvm->mn_active_invalidate_count)

		kvm->mn_active_invalidate_count = 0;

	else

		WARN_ON(kvm->mmu_invalidate_in_progress);

#else

	kvm_flush_shadow_all(kvm);

#endif