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Fri, 17 Apr 2026 09:47:05 -0700 (PDT) Date: Fri, 17 Apr 2026 09:47:04 -0700 In-Reply-To: <0064952b-048c-455d-ad89-e27e5cb82591@linux.dev> Mime-Version: 1.0 References: <20250729225455.670324-1-seanjc@google.com> <20250729225455.670324-25-seanjc@google.com> <0064952b-048c-455d-ad89-e27e5cb82591@linux.dev> Message-ID: Subject: Re: [PATCH v17 24/24] KVM: selftests: Add guest_memfd testcase to fault-in on !mmap()'d memory From: Sean Christopherson To: Zenghui Yu Cc: Paolo Bonzini , Marc Zyngier , Oliver Upton , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, Ira Weiny , Gavin Shan , Shivank Garg , Vlastimil Babka , Xiaoyao Li , David Hildenbrand , Fuad Tabba , Ackerley Tng , Tao Chan , James Houghton Content-Type: text/plain; charset="us-ascii" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260417_094707_770346_BB750063 X-CRM114-Status: GOOD ( 18.22 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Mar 30, 2026, Zenghui Yu wrote: > On 7/30/25 6:54 AM, Sean Christopherson wrote: > > Add a guest_memfd testcase to verify that a vCPU can fault-in guest_memfd > > memory that supports mmap(), but that is not currently mapped into host > > userspace and/or has a userspace address (in the memslot) that points at > > something other than the target guest_memfd range. Mapping guest_memfd > > memory into the guest is supposed to operate completely independently from > > any userspace mappings. > > + vm = __vm_create_shape_with_one_vcpu(VM_SHAPE_DEFAULT, &vcpu, 1, guest_code); > > + > > + TEST_ASSERT(vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_MMAP), > > + "Default VM type should always support guest_memfd mmap()"); > > + > > + size = vm->page_size; > > + fd = vm_create_guest_memfd(vm, size, GUEST_MEMFD_FLAG_MMAP); > > This test fails on arm64 when vm->page_size is 4k and host's page_size > is 64k: > > [root@localhost kvm]# ./guest_memfd_test > Random seed: 0x6b8b4567 > __vm_create: mode='PA-bits:40, VA-bits:48, 4K pages' type='0', pages='660' > ==== Test Assertion Failure ==== > include/kvm_util.h:683: fd >= 0 > pid=889 tid=889 errno=22 - Invalid argument > 1 0x000000000040262b: vm_create_guest_memfd at kvm_util.h:683 > 2 (inlined by) test_guest_memfd_guest at guest_memfd_test.c:450 > 3 (inlined by) main at guest_memfd_test.c:491 > 4 0x00007fff8f56af3b: ?? ??:0 > 5 0x00007fff8f56b007: ?? ??:0 > 6 0x0000000000402a2f: _start at ??:? > KVM_CREATE_GUEST_MEMFD failed, rc: -1 errno: 22 (Invalid argument) Does this fix things for you? If so, I'll send a proper patch. diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c index ec7644aae999..c682bda722f9 100644 --- a/tools/testing/selftests/kvm/guest_memfd_test.c +++ b/tools/testing/selftests/kvm/guest_memfd_test.c @@ -510,9 +510,15 @@ static void test_guest_memfd_guest(void) "Default VM type should support INIT_SHARED, supported flags = 0x%x", vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS)); + /* + * Use the guest's page size for all accesses, e.g. to avoid having to + * map multiple pages, but create the guest_memfd instance with the max + * of the host or guest page size, as KVM requires gmem files to be + * aligned to the host page size. + */ size = vm->page_size; - fd = vm_create_guest_memfd(vm, size, GUEST_MEMFD_FLAG_MMAP | - GUEST_MEMFD_FLAG_INIT_SHARED); + fd = vm_create_guest_memfd(vm, max(size, page_size), GUEST_MEMFD_FLAG_MMAP | + GUEST_MEMFD_FLAG_INIT_SHARED); vm_set_user_memory_region2(vm, slot, KVM_MEM_GUEST_MEMFD, gpa, size, NULL, fd, 0); mem = kvm_mmap(size, PROT_READ | PROT_WRITE, MAP_SHARED, fd);