[PATCH RFC v4 30/44] KVM: selftests: Test that truncation does not change shared/private status
From: Ackerley Tng <hidden>
Date: 2026-03-26 22:25:26
Also in:
kvm, linux-kselftest, linux-mm, linux-trace-kernel, lkml
Subsystem:
kernel selftest framework, kernel virtual machine (kvm), the rest · Maintainers:
Shuah Khan, Paolo Bonzini, Linus Torvalds
Add a test to verify that deallocating a page in a guest memfd region via fallocate() with FALLOC_FL_PUNCH_HOLE does not alter the shared or private status of the corresponding memory range. When a page backing a guest memfd mapping is deallocated, e.g., by punching a hole or truncating the file, and then subsequently faulted back in, the new page must inherit the correct shared/private status tracked by guest_memfd. Signed-off-by: Ackerley Tng <redacted> Co-developed-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com> --- tools/testing/selftests/kvm/guest_memfd_conversions_test.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/tools/testing/selftests/kvm/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/guest_memfd_conversions_test.c
index 8f09671505b32..f195a202b3785 100644
--- a/tools/testing/selftests/kvm/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_conversions_test.c@@ -10,6 +10,7 @@ #include <linux/sizes.h> #include "kvm_util.h" +#include "kvm_syscalls.h" #include "kselftest_harness.h" #include "test_util.h" #include "ucall_common.h"
@@ -320,6 +321,19 @@ GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED(unallocated_folios, 8) test_convert_to_shared(t, i, 'B', 'C', 'D'); } +/* Truncation should not affect shared/private status. */ +GMEM_CONVERSION_TEST_INIT_SHARED(truncate) +{ + host_do_rmw(t->mem, 0, 0, 'A'); + kvm_fallocate(t->gmem_fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page_size); + host_do_rmw(t->mem, 0, 0, 'A'); + + test_convert_to_private(t, 0, 'A', 'B'); + + kvm_fallocate(t->gmem_fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page_size); + test_private(t, 0, 0, 'A'); +} + int main(int argc, char *argv[]) { TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));
--
2.53.0.1018.g2bb0e51243-goog