From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D42E237E31D for ; Mon, 30 Mar 2026 19:44:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774899857; cv=none; b=CXEFJqWeudeUl8rqEWM528GgjHVF3WumdCZjgkEYOycG+0+vILwkWLTIjGwKPR6h+r45/n5pHK7TQEWjFUQzNWqo7CAYJZLjrJUkw8jP0fC7706nQvk9tmbKFI+yr2XCCBn6n8ISlOyJ9f3BTFPGg1E6cZpi32NN1gBWo/RXGVQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774899857; c=relaxed/simple; bh=ipt6Wg4jbId1jrrX6o4juwYcprNfV6dB2AkIftE7XL0=; h=Date:To:From:Subject:Message-Id; b=cbctWVoKSKQIOv9Gblzr/H0sIsBO2BJnpVU2p6eXBBWdx4c3oDNISK3KdTeHi6wZgH5lEF1e2/bFRn+1ur/Jhb7TIsNBRw/R9ykOyjY+h/r7PsmKGpMcrm+CuQYdvotRhLKK3DX1ExNh0/G6m56RSeskVXgvA2MIvcmTbfyBl3E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=LC7I0/F7; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="LC7I0/F7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 71DEAC4CEF7; Mon, 30 Mar 2026 19:44:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1774899857; bh=ipt6Wg4jbId1jrrX6o4juwYcprNfV6dB2AkIftE7XL0=; h=Date:To:From:Subject:From; b=LC7I0/F7Z7uaO2FRZyoS4oohkYKIy4a/5VzSCVrWO++xOvlY0HMlrYZuBj2AWyQju VHRGUoT0/TnkJmjlHqcyaBmwczNYM/2T8lr7LKEF3FJaZAp9m7wMP2uUrIyAHvOyjX l9KnH3dMGgeWFubDL3nPvOS6QnJ43aFxT51arp7c= Date: Mon, 30 Mar 2026 12:44:16 -0700 To: mm-commits@vger.kernel.org,kalyazin@amazon.com,akpm@linux-foundation.org From: Andrew Morton Subject: + kvm-selftests-test-userfaultfd-minor-for-guest_memfd.patch added to mm-unstable branch Message-Id: <20260330194417.71DEAC4CEF7@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: KVM: selftests: test userfaultfd minor for guest_memfd has been added to the -mm mm-unstable branch. Its filename is kvm-selftests-test-userfaultfd-minor-for-guest_memfd.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kvm-selftests-test-userfaultfd-minor-for-guest_memfd.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Nikita Kalyazin Subject: KVM: selftests: test userfaultfd minor for guest_memfd Date: Mon, 30 Mar 2026 13:11:15 +0300 The test demonstrates that a minor userfaultfd event in guest_memfd can be resolved via a memcpy followed by a UFFDIO_CONTINUE ioctl. Link: https://lkml.kernel.org/r/20260330101116.1117699-15-rppt@kernel.org Signed-off-by: Nikita Kalyazin Signed-off-by: Mike Rapoport (Microsoft) Cc: Andrea Arcangeli Cc: Andrei Vagin Cc: Axel Rasmussen Cc: Baolin Wang Cc: David Hildenbrand (Arm) Cc: Harry Yoo Cc: Hugh Dickins Cc: James Houghton Cc: Liam Howlett Cc: Lorenzo Stoakes (Oracle) Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Muchun Song Cc: Oscar Salvador Cc: Paolo Bonzini Cc: Peter Xu Cc: Sean Christopherson Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- tools/testing/selftests/kvm/guest_memfd_test.c | 113 +++++++++++++++ 1 file changed, 113 insertions(+) --- a/tools/testing/selftests/kvm/guest_memfd_test.c~kvm-selftests-test-userfaultfd-minor-for-guest_memfd +++ a/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 "numaif.h" @@ -329,6 +333,112 @@ static void test_create_guest_memfd_mult close(fd1); } +struct fault_args { + char *addr; + 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_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; + const char test_val = 0xcd; + + ret = posix_memalign(&buf, page_size, total_size); + TEST_ASSERT_EQ(ret, 0); + memset(buf, test_val, total_size); + + uffd = syscall(__NR_userfaultfd, O_CLOEXEC); + TEST_ASSERT(uffd != -1, "userfaultfd creation should succeed"); + + struct uffdio_api uffdio_api = { + .api = UFFD_API, + .features = 0, + }; + ret = ioctl(uffd, UFFDIO_API, &uffdio_api); + TEST_ASSERT(ret != -1, "ioctl(UFFDIO_API) should succeed"); + + /* Map the guest_memfd twice: once with UFFD registered, once without */ + 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"); + + /* Register UFFD_MINOR on the first mapping */ + 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"); + + /* + * Populate the page in the page cache first via mem_nofault. + * This is required for UFFD_MINOR - the page must exist in the cache. + * Write test data to the page. + */ + memcpy(mem_nofault + offset, buf + offset, page_size); + + /* + * Now access the same page via mem (which has UFFD_MINOR registered). + * Since the page exists in the cache, this should trigger UFFD_MINOR. + */ + 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"); + TEST_ASSERT(msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_MINOR, + "pagefault should be minor fault"); + + /* Resolve the minor fault with UFFDIO_CONTINUE */ + 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 the faulting thread to complete */ + ret = pthread_join(fault_thread, NULL); + TEST_ASSERT(ret == 0, "pthread_join should succeed"); + + /* Verify the thread read the correct value */ + TEST_ASSERT(args.value == test_val, + "memory should contain the value that was written"); + TEST_ASSERT(*(char *)(mem + offset) == test_val, + "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); +} + static void test_guest_memfd_flags(struct kvm_vm *vm) { uint64_t valid_flags = vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS); @@ -383,6 +493,9 @@ static void __test_guest_memfd(struct kv gmem_test(file_size, vm, flags); gmem_test(fallocate, vm, flags); gmem_test(invalid_punch_hole, vm, flags); + + if (flags & GUEST_MEMFD_FLAG_INIT_SHARED) + gmem_test(uffd_minor, vm, flags); } static void test_guest_memfd(unsigned long vm_type) _ Patches currently in -mm which might be from kalyazin@amazon.com are kvm-guest_memfd-implement-userfaultfd-operations.patch kvm-selftests-test-userfaultfd-minor-for-guest_memfd.patch kvm-selftests-test-userfaultfd-missing-for-guest_memfd.patch