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Wed, 26 Nov 2025 16:49:50 +0000 (UTC) X-Farcaster-Flow-ID: 2808e225-d96e-4595-94bf-b76a6f3bfa50 Received: from EX19D005EUB003.ant.amazon.com (10.252.51.31) by EX19MTAEUB002.ant.amazon.com (10.252.51.79) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.29; Wed, 26 Nov 2025 16:49:49 +0000 Received: from [192.168.8.204] (10.106.83.30) by EX19D005EUB003.ant.amazon.com (10.252.51.31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.29; Wed, 26 Nov 2025 16:49:47 +0000 Message-ID: <18b4cddb-3e04-4272-9f04-6857cea70ff5@amazon.com> Date: Wed, 26 Nov 2025 16:49:46 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Reply-To: Subject: Re: [PATCH v2 5/5] KVM: selftests: test userfaultfd minor for guest_memfd To: Mike Rapoport , CC: Andrea Arcangeli , Andrew Morton , Axel Rasmussen , Baolin Wang , David Hildenbrand , Hugh Dickins , James Houghton , "Liam R. Howlett" , "Lorenzo Stoakes" , Michal Hocko , "Paolo Bonzini" , Peter Xu , "Sean Christopherson" , Shuah Khan , "Suren Baghdasaryan" , Vlastimil Babka , , , References: <20251125183840.2368510-1-rppt@kernel.org> <20251125183840.2368510-6-rppt@kernel.org> Content-Language: en-US From: Nikita Kalyazin Autocrypt: addr=kalyazin@amazon.com; keydata= xjMEY+ZIvRYJKwYBBAHaRw8BAQdA9FwYskD/5BFmiiTgktstviS9svHeszG2JfIkUqjxf+/N JU5pa2l0YSBLYWx5YXppbiA8a2FseWF6aW5AYW1hem9uLmNvbT7CjwQTFggANxYhBGhhGDEy BjLQwD9FsK+SyiCpmmTzBQJnrNfABQkFps9DAhsDBAsJCAcFFQgJCgsFFgIDAQAACgkQr5LK IKmaZPOpfgD/exazh4C2Z8fNEz54YLJ6tuFEgQrVQPX6nQ/PfQi2+dwBAMGTpZcj9Z9NvSe1 CmmKYnYjhzGxzjBs8itSUvWIcMsFzjgEY+ZIvRIKKwYBBAGXVQEFAQEHQCqd7/nb2tb36vZt ubg1iBLCSDctMlKHsQTp7wCnEc4RAwEIB8J+BBgWCAAmFiEEaGEYMTIGMtDAP0Wwr5LKIKma ZPMFAmes18AFCQWmz0MCGwwACgkQr5LKIKmaZPNTlQEA+q+rGFn7273rOAg+rxPty0M8lJbT i2kGo8RmPPLu650A/1kWgz1AnenQUYzTAFnZrKSsXAw5WoHaDLBz9kiO5pAK In-Reply-To: <20251125183840.2368510-6-rppt@kernel.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.106.83.30] X-ClientProxiedBy: EX19D002EUC001.ant.amazon.com (10.252.51.219) To EX19D005EUB003.ant.amazon.com (10.252.51.31) X-Rspamd-Queue-Id: 732C9180004 X-Rspamd-Server: rspam02 X-Stat-Signature: hcy3w44ixkqd1kpn6ododr8tmno4ikts X-Rspam-User: X-HE-Tag: 1764175809-794810 X-HE-Meta: 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 bTPZ2bcj 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 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: On 25/11/2025 18:38, Mike Rapoport wrote: > 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, Should it be UFFD_FEATURE_MINOR_SHMEM instead? UFFD_FEATURE_MINOR_GENERIC was removed in the v1. > + }; > + 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 >