Hi This series is for a bug where userspace can request KVM to reset dirty GFNs belonging to a memslot that does not enable dirty tracking. Patch 1 provides the fix, which can be applied to Linux 6.13-rc3. Although the fix is a generic one, its primary motivation is to prevent userspace from triggering write permission reduction or accessed bit clearing in mirror SPTEs within TDX VMs. This could otherwise cause mismatches between mirror SPTEs and the corresponding external SPTEs, and in the worst case, lead to the removal of the external SPTEs. Patch 2 introduces a selftest for TDX VMs to demonstrate how userspace could trigger this bug. If necessary, this test can be ported to the generic KVM selftest (e.g., dirty_log_test). v2: - Added a comment in patch 1, explaining that it's possible to try to update a memslot that isn't being dirty-logged if userspace is misbehaving. Specifically, userspace can write arbitrary data into the ring. (Sean) v1: https://lore.kernel.org/all/20241220082027.15851-1-yan.y.zhao@xxxxxxxxx/ Thanks Yan Yan Zhao (2): KVM: Do not reset dirty GFNs in a memslot not enabling dirty tracking KVM: selftests: TDX: Test dirty ring on a gmemfd slot tools/testing/selftests/kvm/Makefile | 1 + .../selftests/kvm/x86_64/tdx_dirty_ring.c | 231 ++++++++++++++++++ virt/kvm/dirty_ring.c | 8 +- 3 files changed, 239 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/kvm/x86_64/tdx_dirty_ring.c -- 2.43.2
