kernel.git/tools/testing/selftests/kvm/guest_memfd_test.c, branch master

KVM: selftests: Increase 'maxnode' for guest_memfd tests

2026-03-11T17:41:10Z

Increase 'maxnode' when using 'get_mempolicy' syscall in guest_memfd mmap and NUMA policy tests to fix a failure on one Intel GNR platform. On a CXL-capable platform, the memory affinity of CXL memory regions may not be covered by the SRAT. Since each CXL memory region is enumerated via a CFMWS table, at early boot the kernel parses all CFMWS tables to detect all CXL memory regions and assigns a 'faked' NUMA node for each of them, starting from the highest NUMA node ID enumerated via the SRAT. This increases the 'nr_node_ids'. E.g., on the aforementioned Intel GNR platform which has 4 NUMA nodes and 18 CFMWS tables, it increases to 22. This results in the 'get_mempolicy' syscall failure on that platform, because currently 'maxnode' is hard-coded to 8 but the 'get_mempolicy' syscall requires the 'maxnode' to be not smaller than the 'nr_node_ids'. Increase the 'maxnode' to the number of bits of 'nodemask', which is 'unsigned long', to fix this. This may not cover all systems. Perhaps a better way is to always set the 'nodemask' and 'maxnode' based on the actual maximum NUMA node ID on the system, but for now just do the simple way. Reported-by: Yi Lai Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221014 Closes: https://lore.kernel.org/all/bug-221014-28872@https.bugzilla.kernel.org%2F Signed-off-by: Kai Huang Reviewed-by: Yuan Yao Link: https://patch.msgid.link/20260302205158.178058-1-kai.huang@intel.com Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini

KVM: selftests: Add guest_memfd tests for mmap and NUMA policy support

2025-10-20T13:30:45Z

Add tests for NUMA memory policy binding and NUMA aware allocation in guest_memfd. This extends the existing selftests by adding proper validation for: - KVM GMEM set_policy and get_policy() vm_ops functionality using mbind() and get_mempolicy() - NUMA policy application before and after memory allocation Run the NUMA mbind() test with and without INIT_SHARED, as KVM should allow doing mbind(), madvise(), etc. on guest-private memory, e.g. so that userspace can set NUMA policy for CoCo VMs. Run the NUMA allocation test only for INIT_SHARED, i.e. if the host can't fault-in memory (via direct access, madvise(), etc.) as move_pages() returns -ENOENT if the page hasn't been faulted in (walks the host page tables to find the associated folio) [sean: don't skip entire test when running on non-NUMA system, test mbind() with private memory, provide more info in assert messages] Signed-off-by: Shivank Garg Tested-by: Ashish Kalra Link: https://lore.kernel.org/r/20251016172853.52451-12-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: selftests: Verify that reads to inaccessible guest_memfd VMAs SIGBUS

2025-10-10T21:25:30Z

Expand the guest_memfd negative testcases for overflow and MAP_PRIVATE to verify that reads to inaccessible memory also get a SIGBUS. Reviewed-by: Ackerley Tng Tested-by: Ackerley Tng Reviewed-by: Lisa Wang Tested-by: Lisa Wang Link: https://lore.kernel.org/r/20251003232606.4070510-14-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: selftests: Verify that faulting in private guest_memfd memory fails

2025-10-10T21:25:30Z

Add a guest_memfd testcase to verify that faulting in private memory gets a SIGBUS. For now, test only the case where memory is private by default since KVM doesn't yet support in-place conversion. Deliberately run the CoW test with and without INIT_SHARED set as KVM should disallow MAP_PRIVATE regardless of whether the memory itself is private from a CoCo perspective. Cc: Ackerley Tng Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba Reviewed-by: David Hildenbrand Reviewed-by: Ackerley Tng Tested-by: Ackerley Tng Link: https://lore.kernel.org/r/20251003232606.4070510-13-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: selftests: Add wrapper macro to handle and assert on expected SIGBUS

2025-10-10T21:25:29Z

Extract the guest_memfd test's SIGBUS handling functionality into a common TEST_EXPECT_SIGBUS() macro in anticipation of adding more SIGBUS testcases. Eating a SIGBUS isn't terrible difficult, but it requires a non-trivial amount of boilerplate code, and using a macro allows selftests to print out the exact action that failed to generate a SIGBUS without the developer needing to remember to add a useful error message. Explicitly mark the SIGBUS handler as "used", as gcc-14 at least likes to discard the function before linking. Opportunistically use TEST_FAIL(...) instead of TEST_ASSERT(false, ...), and fix the write path of the guest_memfd test to use the local "val" instead of hardcoding the literal value a second time. Suggested-by: Ackerley Tng Reviewed-by: Ackerley Tng Tested-by: Ackerley Tng Reviewed-by: Lisa Wang Tested-by: Lisa Wang Link: https://lore.kernel.org/r/20251003232606.4070510-12-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: selftests: Isolate the guest_memfd Copy-on-Write negative testcase

2025-10-10T21:25:28Z

Move the guest_memfd Copy-on-Write (CoW) testcase to its own function to better separate positive testcases from negative testcases. No functional change intended. Suggested-by: Ackerley Tng Reviewed-by: Ackerley Tng Tested-by: Ackerley Tng Link: https://lore.kernel.org/r/20251003232606.4070510-11-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: selftests: Add wrappers for mmap() and munmap() to assert success

2025-10-10T21:25:28Z

Add and use wrappers for mmap() and munmap() that assert success to reduce a significant amount of boilerplate code, to ensure all tests assert on failure, and to provide consistent error messages on failure. No functional change intended. Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba Reviewed-by: David Hildenbrand Reviewed-by: Ackerley Tng Link: https://lore.kernel.org/r/20251003232606.4070510-10-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: selftests: Add test coverage for guest_memfd without GUEST_MEMFD_FLAG_MMAP

2025-10-10T21:25:27Z

If a VM type supports KVM_CAP_GUEST_MEMFD_MMAP, the guest_memfd test will run all test cases with GUEST_MEMFD_FLAG_MMAP set. This leaves the code path for creating a non-mmap()-able guest_memfd on a VM that supports mappable guest memfds untested. Refactor the test to run the main test suite with a given set of flags. Then, for VM types that support the mappable capability, invoke the test suite twice: once with no flags, and once with GUEST_MEMFD_FLAG_MMAP set. This ensures both creation paths are properly exercised on capable VMs. Run test_guest_memfd_flags() only once per VM type since it depends only on the set of valid/supported flags, i.e. iterating over an arbitrary set of flags is both unnecessary and wrong. Signed-off-by: Ackerley Tng [sean: use double-underscores for the inner helper] Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba Reviewed-by: David Hildenbrand Link: https://lore.kernel.org/r/20251003232606.4070510-9-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: selftests: Create a new guest_memfd for each testcase

2025-10-10T21:25:26Z

Refactor the guest_memfd selftest to improve test isolation by creating a a new guest_memfd for each testcase. Currently, the test reuses a single guest_memfd instance for all testcases, and thus creates dependencies between tests, e.g. not truncating folios from the guest_memfd instance at the end of a test could lead to unexpected results (see the PUNCH_HOLE purging that needs to done by in-flight the NUMA testcases[1]). Invoke each test via a macro wrapper to create and close a guest_memfd to cut down on the boilerplate copy+paste needed to create a test. Link: https://lore.kernel.org/all/20250827175247.83322-10-shivankg@amd.com Reported-by: Ackerley Tng Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba Reviewed-by: David Hildenbrand Reviewed-by: Ackerley Tng Tested-by: Ackerley Tng Link: https://lore.kernel.org/r/20251003232606.4070510-8-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: selftests: Stash the host page size in a global in the guest_memfd test

2025-10-10T21:25:26Z

Use a global variable to track the host page size in the guest_memfd test so that the information doesn't need to be constantly passed around. The state is purely a reflection of the underlying system, i.e. can't be set by the test and is constant for a given invocation of the test, and thus explicitly passing the host page size to individual testcases adds no value, e.g. doesn't allow testing different combinations. Making page_size a global will simplify an upcoming change to create a new guest_memfd instance per testcase. No functional change intended. Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba Reviewed-by: David Hildenbrand Reviewed-by: Ackerley Tng Tested-by: Ackerley Tng Link: https://lore.kernel.org/r/20251003232606.4070510-7-seanjc@google.com Signed-off-by: Sean Christopherson