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AJvYcCVFaySaPkIVpE2wnJjaEvrL+sFKp4dy7gP5cDfWH70yVm6VFsLNbOnExymh13B1yp6Xp35y7UGFpB6SSkg=@vger.kernel.org X-Gm-Message-State: AOJu0Yw7w//yKuT5VKjoBB/SUz9pbXWbxW7b+mdiB6Wkpqm+4NmfMIrH T/9o5mIQSZHMBvqPJxYcn8K4YxWQ2moZ72yrdoiRRg3X+o7sxJ/vxU0HvfJwgAA26KlsW0Ym5fo D9mBbzLS368peiZOHFSHxPMPV4g== X-Received: from pjbqx5.prod.google.com ([2002:a17:90b:3e45:b0:352:e2af:ed76]) (user=ackerleytng job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:2dc7:b0:340:2a3a:71b7 with SMTP id 98e67ed59e1d1-3543b30027cmr12312576a91.12.1770071466169; Mon, 02 Feb 2026 14:31:06 -0800 (PST) Date: Mon, 2 Feb 2026 14:30:05 -0800 In-Reply-To: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: X-Mailer: git-send-email 2.53.0.rc1.225.gd81095ad13-goog Message-ID: <73b986861dedf768d270a95c4fa259976b5f1d42.1770071243.git.ackerleytng@google.com> Subject: [RFC PATCH v2 27/37] KVM: selftests: Test that shared/private status is consistent across processes From: Ackerley Tng To: kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org Cc: aik@amd.com, andrew.jones@linux.dev, binbin.wu@linux.intel.com, bp@alien8.de, brauner@kernel.org, chao.p.peng@intel.com, chao.p.peng@linux.intel.com, chenhuacai@kernel.org, corbet@lwn.net, dave.hansen@linux.intel.com, david@kernel.org, hpa@zytor.com, ira.weiny@intel.com, jgg@nvidia.com, jmattson@google.com, jroedel@suse.de, jthoughton@google.com, maobibo@loongson.cn, mathieu.desnoyers@efficios.com, maz@kernel.org, mhiramat@kernel.org, michael.roth@amd.com, mingo@redhat.com, mlevitsk@redhat.com, oupton@kernel.org, pankaj.gupta@amd.com, pbonzini@redhat.com, prsampat@amd.com, qperret@google.com, ricarkol@google.com, rick.p.edgecombe@intel.com, rientjes@google.com, rostedt@goodmis.org, seanjc@google.com, shivankg@amd.com, shuah@kernel.org, steven.price@arm.com, tabba@google.com, tglx@linutronix.de, vannapurve@google.com, vbabka@suse.cz, willy@infradead.org, wyihan@google.com, yan.y.zhao@intel.com, Ackerley Tng Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Sean Christopherson Add a test to verify that a guest_memfd's shared/private status is consistent across processes, and that any shared pages previously mapped in any process are unmapped from all processes. The test forks a child process after creating the shared guest_memfd region so that the second process exists alongside the main process for the entire test. The processes then take turns to access memory to check that the shared/private status is consistent across processes. Signed-off-by: Sean Christopherson Co-developed-by: Ackerley Tng Signed-off-by: Ackerley Tng --- .../kvm/guest_memfd_conversions_test.c | 74 +++++++++++++++++++ 1 file changed, 74 insertions(+) diff --git a/tools/testing/selftests/kvm/guest_memfd_conversions_test.c b/t= ools/testing/selftests/kvm/guest_memfd_conversions_test.c index 89881a71902e..c1a9cc7c9fae 100644 --- a/tools/testing/selftests/kvm/guest_memfd_conversions_test.c +++ b/tools/testing/selftests/kvm/guest_memfd_conversions_test.c @@ -322,6 +322,80 @@ GMEM_CONVERSION_TEST_INIT_SHARED(truncate) test_private(t, 0, 0, 'A'); } =20 +/* Test that shared/private memory protections work and are seen from any = process. */ +GMEM_CONVERSION_TEST_INIT_SHARED(forked_accesses) +{ + /* + * No races are intended in this test, shared memory is only used to + * coordinate between processes. + */ + static enum { + STATE_INIT, + STATE_CHECK_SHARED, + STATE_DONE_CHECKING_SHARED, + STATE_CHECK_PRIVATE, + STATE_DONE_CHECKING_PRIVATE, + } *test_state; + pid_t child_pid; + + test_state =3D kvm_mmap(sizeof(*test_state), PROT_READ | PROT_WRITE, + MAP_SHARED | MAP_ANONYMOUS, -1); + +#define TEST_STATE_AWAIT(__state) \ + while (READ_ONCE(*test_state) !=3D __state) { \ + if (child_pid !=3D 0) { \ + int status; \ + pid_t pid; \ + do { \ + pid =3D waitpid(child_pid, &status, WNOHANG); \ + } while (pid =3D=3D -1 && errno =3D=3D EINTR); \ + if (pid =3D=3D -1) \ + TEST_FAIL("Couldn't check child status."); \ + else if (pid !=3D 0) \ + TEST_FAIL("Child exited prematurely."); \ + } \ + } + +#define TEST_STATE_SET(__state) WRITE_ONCE(*test_state, __state) + + child_pid =3D fork(); + TEST_ASSERT(child_pid !=3D -1, "fork failed"); + + if (child_pid =3D=3D 0) { + const char inconsequential =3D 0xdd; + + TEST_STATE_AWAIT(STATE_CHECK_SHARED); + + /* + * This maps the pages into the child process as well, and tests + * that the conversion process will unmap the guest_memfd memory + * from all processes. + */ + host_do_rmw(t->mem, 0, 0xB, 0xC); + + TEST_STATE_SET(STATE_DONE_CHECKING_SHARED); + TEST_STATE_AWAIT(STATE_CHECK_PRIVATE); + + TEST_EXPECT_SIGBUS(READ_ONCE(t->mem[0])); + TEST_EXPECT_SIGBUS(WRITE_ONCE(t->mem[0], inconsequential)); + + TEST_STATE_SET(STATE_DONE_CHECKING_PRIVATE); + exit(0); + } + + test_shared(t, 0, 0, 0xA, 0xB); + + TEST_STATE_SET(STATE_CHECK_SHARED); + TEST_STATE_AWAIT(STATE_DONE_CHECKING_SHARED); + + test_convert_to_private(t, 0, 0xC, 0xD); + + TEST_STATE_SET(STATE_CHECK_PRIVATE); + TEST_STATE_AWAIT(STATE_DONE_CHECKING_PRIVATE); + + kvm_munmap(test_state, sizeof(*test_state)); +} + int main(int argc, char *argv[]) { TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_V= M)); --=20 2.53.0.rc1.225.gd81095ad13-goog