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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: [PATCH 5/5] KVM: selftests: test userfaultfd minor for guest_memfd Date: Sun, 23 Nov 2025 12:27:07 +0200 Message-ID: <20251123102707.559422-6-rppt@kernel.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20251123102707.559422-1-rppt@kernel.org> References: <20251123102707.559422-1-rppt@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 3479DC0011 X-Stat-Signature: ornn55yoam8j1gfnqdnpb188wsq6jbus X-Rspam-User: X-HE-Tag: 1763893666-307838 X-HE-Meta: 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 vXeODGkZ MzX+YopdUifdR4Yj6EY/JRKxej8n2Ce1ZYxs99B/DslrJdZ+raZoVAimxK6PZWxcrrVxmIGXvsC49L+bMh5LTCDIuiwyQfzQL9FXAy4LBo4ipFUBiAAYBS5SiKb34wC1VkclHjbNQCq7dr1PzFLbAqLk9t5iKl+WB7JdmS40AwCziBihRXh4h1KX92EZCO7L5gAxgc4hN39rBPLo0J1TjC5oow2xhxRFbB0f2kO9g9pPzYRskLkncJ60mDBXP8JjfQ2CH+acy84uuyoJG2L5prbs8E2QVvTp6F6fNbYQgo75U0W6wCqK/3i/NMQ== 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