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Fri, 12 Sep 2025 09:17:59 +0000 (UTC) X-Farcaster-Flow-ID: 0791345b-5f96-4e3a-80ef-d080c8c5816b Received: from EX19D015EUB004.ant.amazon.com (10.252.51.13) by EX19MTAEUC002.ant.amazon.com (10.252.51.181) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.20; Fri, 12 Sep 2025 09:17:48 +0000 Received: from EX19D015EUB004.ant.amazon.com (10.252.51.13) by EX19D015EUB004.ant.amazon.com (10.252.51.13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.20; Fri, 12 Sep 2025 09:17:47 +0000 Received: from EX19D015EUB004.ant.amazon.com ([fe80::2dc9:7aa9:9cd3:fc8a]) by EX19D015EUB004.ant.amazon.com ([fe80::2dc9:7aa9:9cd3:fc8a%3]) with mapi id 15.02.2562.020; Fri, 12 Sep 2025 09:17:47 +0000 From: "Roy, Patrick" CC: "Thomson, Jack" , "Kalyazin, Nikita" , "Cali, Marco" , "derekmn@amazon.co.uk" , "Roy, Patrick" , "willy@infradead.org" , "corbet@lwn.net" , "pbonzini@redhat.com" , "maz@kernel.org" , "oliver.upton@linux.dev" , "joey.gouly@arm.com" , "suzuki.poulose@arm.com" , "yuzenghui@huawei.com" , "catalin.marinas@arm.com" , "will@kernel.org" , "chenhuacai@kernel.org" , "kernel@xen0n.name" , "paul.walmsley@sifive.com" , "palmer@dabbelt.com" , "aou@eecs.berkeley.edu" , "alex@ghiti.fr" , "agordeev@linux.ibm.com" , "gerald.schaefer@linux.ibm.com" , "hca@linux.ibm.com" , "gor@linux.ibm.com" , "borntraeger@linux.ibm.com" , "svens@linux.ibm.com" , "dave.hansen@linux.intel.com" , "luto@kernel.org" , "peterz@infradead.org" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "x86@kernel.org" , "hpa@zytor.com" , "trondmy@kernel.org" , "anna@kernel.org" , "hubcap@omnibond.com" , "martin@omnibond.com" , "viro@zeniv.linux.org.uk" , "brauner@kernel.org" , "jack@suse.cz" , "akpm@linux-foundation.org" , "david@redhat.com" , "lorenzo.stoakes@oracle.com" , "Liam.Howlett@oracle.com" , "vbabka@suse.cz" , "rppt@kernel.org" , "surenb@google.com" , "mhocko@suse.com" , "ast@kernel.org" , "daniel@iogearbox.net" , "andrii@kernel.org" , "martin.lau@linux.dev" , "eddyz87@gmail.com" , "song@kernel.org" , "yonghong.song@linux.dev" , "john.fastabend@gmail.com" , "kpsingh@kernel.org" , "sdf@fomichev.me" , "haoluo@google.com" , "jolsa@kernel.org" , "jgg@ziepe.ca" , "jhubbard@nvidia.com" , "peterx@redhat.com" , "jannh@google.com" , "pfalcato@suse.de" , "axelrasmussen@google.com" , "yuanchu@google.com" , "weixugc@google.com" , "hannes@cmpxchg.org" , "zhengqi.arch@bytedance.com" , "shakeel.butt@linux.dev" , "shuah@kernel.org" , "seanjc@google.com" , "linux-fsdevel@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "kvmarm@lists.linux.dev" , "loongarch@lists.linux.dev" , "linux-riscv@lists.infradead.org" , "linux-s390@vger.kernel.org" , "linux-nfs@vger.kernel.org" , "devel@lists.orangefs.org" , "linux-mm@kvack.org" , "bpf@vger.kernel.org" , "linux-kselftest@vger.kernel.org" Subject: [PATCH v6 11/11] KVM: selftests: Test guest execution from direct map removed gmem Thread-Topic: [PATCH v6 11/11] KVM: selftests: Test guest execution from direct map removed gmem Thread-Index: AQHcI8YabQ9AygaqQUCaf6AaD/P8kg== Date: Fri, 12 Sep 2025 09:17:47 +0000 Message-ID: <20250912091708.17502-12-roypat@amazon.co.uk> References: <20250912091708.17502-1-roypat@amazon.co.uk> In-Reply-To: <20250912091708.17502-1-roypat@amazon.co.uk> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Add a selftest that loads itself into guest_memfd (via GUEST_MEMFD_FLAG_MMAP) and triggers an MMIO exit when executed. This exercises x86 MMIO emulation code inside KVM for guest_memfd-backed memslots where the guest_memfd folios are direct map removed. Particularly, it validates that x86 MMIO emulation code (guest page table walks + instruction fetch) correctly accesses gmem through the VMA that's been reflected into the memslot's userspace_addr field (instead of trying to do direct map accesses). Signed-off-by: Patrick Roy --- .../selftests/kvm/set_memory_region_test.c | 50 +++++++++++++++++-- 1 file changed, 46 insertions(+), 4 deletions(-) diff --git a/tools/testing/selftests/kvm/set_memory_region_test.c b/tools/t= esting/selftests/kvm/set_memory_region_test.c index ce3ac0fd6dfb..cb3bc642d376 100644 --- a/tools/testing/selftests/kvm/set_memory_region_test.c +++ b/tools/testing/selftests/kvm/set_memory_region_test.c @@ -603,6 +603,41 @@ static void test_mmio_during_vectoring(void) =20 kvm_vm_free(vm); } + +static void guest_code_trigger_mmio(void) +{ + /* + * Read some GPA that is not backed by a memslot. KVM consider this + * as MMIO and tell userspace to emulate the read. + */ + READ_ONCE(*((uint64_t *)MEM_REGION_GPA)); + + GUEST_DONE(); +} + +static void test_guest_memfd_mmio(void) +{ + struct kvm_vm *vm; + struct kvm_vcpu *vcpu; + struct vm_shape shape =3D { + .mode =3D VM_MODE_DEFAULT, + .src_type =3D VM_MEM_SRC_GUEST_MEMFD_NO_DIRECT_MAP, + }; + pthread_t vcpu_thread; + + pr_info("Testing MMIO emulation for instructions in gmem\n"); + + vm =3D __vm_create_shape_with_one_vcpu(shape, &vcpu, 0, guest_code_trigge= r_mmio); + + virt_map(vm, MEM_REGION_GPA, MEM_REGION_GPA, 1); + + pthread_create(&vcpu_thread, NULL, vcpu_worker, vcpu); + + /* If the MMIO read was successfully emulated, the vcpu thread will exit = */ + pthread_join(vcpu_thread, NULL); + + kvm_vm_free(vm); +} #endif =20 int main(int argc, char *argv[]) @@ -626,10 +661,17 @@ int main(int argc, char *argv[]) test_add_max_memory_regions(); =20 #ifdef __x86_64__ - if (kvm_has_cap(KVM_CAP_GUEST_MEMFD) && - (kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM))) { - test_add_private_memory_region(); - test_add_overlapping_private_memory_regions(); + if (kvm_has_cap(KVM_CAP_GUEST_MEMFD)) { + if (kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM)) { + test_add_private_memory_region(); + test_add_overlapping_private_memory_regions(); + } + + if (kvm_has_cap(KVM_CAP_GUEST_MEMFD_MMAP) && + kvm_has_cap(KVM_CAP_GUEST_MEMFD_NO_DIRECT_MAP)) + test_guest_memfd_mmio(); + else + pr_info("Skipping tests requiring KVM_CAP_GUEST_MEMFD_MMAP | KVM_CAP_GU= EST_MEMFD_NO_DIRECT_MAP"); } else { pr_info("Skipping tests for KVM_MEM_GUEST_MEMFD memory regions\n"); } --=20 2.50.1