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Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Nikita Kalyazin , Paolo Bonzini , Peter Xu , Sean Christopherson , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [RFC PATCH 4/4] KVM: selftests: test userfaultfd minor for guest_memfd Date: Mon, 17 Nov 2025 13:46:31 +0200 Message-ID: <20251117114631.2029447-5-rppt@kernel.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20251117114631.2029447-1-rppt@kernel.org> References: <20251117114631.2029447-1-rppt@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 28DD280017 X-Stat-Signature: x44tucxehm7h1bbitdsoq7c3ax31omth X-Rspam-User: X-HE-Tag: 1763380022-419497 X-HE-Meta: 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 6DKp8kA5 Q8GJM+bDg6594kRdpLLfvHBgBhtD8owaRY2u7MkKc5W3lxKN+sX2jqz4CRZk2yCZ4RZ7iwffPhCDJ/FeFui3h+8s0R/9NW3/O5ZQ7cjFqeOC7DoOuLV/0mJd+mfaGNttMjBbJFCkJCH6iM3kqmhwW34A73goalspASXyNxSClc/z8oNTfocN2ZGpQ6PEtOQWbpizUaCOqaJp3XtLDrLkSxMk19Iq/0TvdOjvAFOdy/zCLq8dSGJtMi9KNtTNDybQtYYLP+JyzrzKaFZuXnrR0k9cZRRAcXNDYwFwXoel+0ljLfYs= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Nikita Kalyazin The test demonstrates that a minor userfaultfd event in guest_memfd can be resolved via a memcpy followed by a UFFDIO_CONTINUE ioctl. Signed-off-by: Nikita Kalyazin Co-developed-by: Mike Rapoport (Microsoft) Signed-off-by: Mike Rapoport (Microsoft) --- .../testing/selftests/kvm/guest_memfd_test.c | 103 ++++++++++++++++++ 1 file changed, 103 insertions(+) diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c index e7d9aeb418d3..a5d3ed21d7bb 100644 --- a/tools/testing/selftests/kvm/guest_memfd_test.c +++ b/tools/testing/selftests/kvm/guest_memfd_test.c @@ -10,13 +10,17 @@ #include #include #include +#include #include #include #include +#include #include #include #include +#include +#include #include "kvm_util.h" #include "test_util.h" @@ -254,6 +258,104 @@ static void test_guest_memfd_flags(struct kvm_vm *vm) } } +struct fault_args { + char *addr; + volatile char value; +}; + +static void *fault_thread_fn(void *arg) +{ + struct fault_args *args = arg; + + /* Trigger page fault */ + args->value = *args->addr; + return NULL; +} + +static void test_uffd_minor(int fd, size_t total_size) +{ + struct uffdio_api uffdio_api = { + .api = UFFD_API, + .features = UFFD_FEATURE_MINOR_GENERIC, + }; + struct uffdio_register uffd_reg; + struct uffdio_continue uffd_cont; + struct uffd_msg msg; + struct fault_args args; + pthread_t fault_thread; + void *mem, *mem_nofault, *buf = NULL; + int uffd, ret; + off_t offset = page_size; + void *fault_addr; + + ret = posix_memalign(&buf, page_size, total_size); + TEST_ASSERT_EQ(ret, 0); + + memset(buf, 0xaa, total_size); + + uffd = syscall(__NR_userfaultfd, O_CLOEXEC); + TEST_ASSERT(uffd != -1, "userfaultfd creation should succeed"); + + ret = ioctl(uffd, UFFDIO_API, &uffdio_api); + TEST_ASSERT(ret != -1, "ioctl(UFFDIO_API) should succeed"); + + mem = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); + TEST_ASSERT(mem != MAP_FAILED, "mmap should succeed"); + + mem_nofault = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); + TEST_ASSERT(mem_nofault != MAP_FAILED, "mmap should succeed"); + + uffd_reg.range.start = (unsigned long)mem; + uffd_reg.range.len = total_size; + uffd_reg.mode = UFFDIO_REGISTER_MODE_MINOR; + ret = ioctl(uffd, UFFDIO_REGISTER, &uffd_reg); + TEST_ASSERT(ret != -1, "ioctl(UFFDIO_REGISTER) should succeed"); + + ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, + offset, page_size); + TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) should succeed"); + + fault_addr = mem + offset; + args.addr = fault_addr; + + ret = pthread_create(&fault_thread, NULL, fault_thread_fn, &args); + TEST_ASSERT(ret == 0, "pthread_create should succeed"); + + ret = read(uffd, &msg, sizeof(msg)); + TEST_ASSERT(ret != -1, "read from userfaultfd should succeed"); + TEST_ASSERT(msg.event == UFFD_EVENT_PAGEFAULT, "event type should be pagefault"); + TEST_ASSERT((void *)(msg.arg.pagefault.address & ~(page_size - 1)) == fault_addr, + "pagefault should occur at expected address"); + + memcpy(mem_nofault + offset, buf + offset, page_size); + + uffd_cont.range.start = (unsigned long)fault_addr; + uffd_cont.range.len = page_size; + uffd_cont.mode = 0; + ret = ioctl(uffd, UFFDIO_CONTINUE, &uffd_cont); + TEST_ASSERT(ret != -1, "ioctl(UFFDIO_CONTINUE) should succeed"); + + /* + * wait for fault_thread to finish to make sure fault happened and was + * resolved before we verify the values + */ + ret = pthread_join(fault_thread, NULL); + TEST_ASSERT(ret == 0, "pthread_join should succeed"); + + TEST_ASSERT(args.value == *(char *)(mem_nofault + offset), + "memory should contain the value that was copied"); + TEST_ASSERT(args.value == *(char *)(mem + offset), + "no further fault is expected"); + + ret = munmap(mem_nofault, total_size); + TEST_ASSERT(!ret, "munmap should succeed"); + + ret = munmap(mem, total_size); + TEST_ASSERT(!ret, "munmap should succeed"); + free(buf); + close(uffd); +} + #define gmem_test(__test, __vm, __flags) \ do { \ int fd = vm_create_guest_memfd(__vm, page_size * 4, __flags); \ @@ -273,6 +375,7 @@ static void __test_guest_memfd(struct kvm_vm *vm, uint64_t flags) if (flags & GUEST_MEMFD_FLAG_INIT_SHARED) { gmem_test(mmap_supported, vm, flags); gmem_test(fault_overflow, vm, flags); + gmem_test(uffd_minor, vm, flags); } else { gmem_test(fault_private, vm, flags); } -- 2.50.1