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Wed, 14 Jan 2026 13:46:43 +0000 Received: from EX19D005EUB003.ant.amazon.com ([fe80::b825:becb:4b38:da0c]) by EX19D005EUB003.ant.amazon.com ([fe80::b825:becb:4b38:da0c%3]) with mapi id 15.02.2562.035; Wed, 14 Jan 2026 13:46:43 +0000 From: "Kalyazin, Nikita" To: "kvm@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "kvmarm@lists.linux.dev" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "bpf@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "kernel@xen0n.name" , "linux-riscv@lists.infradead.org" , "linux-s390@vger.kernel.org" , "loongarch@lists.linux.dev" CC: "pbonzini@redhat.com" , "corbet@lwn.net" , "maz@kernel.org" , "oupton@kernel.org" , "joey.gouly@arm.com" , "suzuki.poulose@arm.com" , "yuzenghui@huawei.com" , "catalin.marinas@arm.com" , "will@kernel.org" , "seanjc@google.com" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "x86@kernel.org" , "hpa@zytor.com" , "luto@kernel.org" , "peterz@infradead.org" , "willy@infradead.org" , "akpm@linux-foundation.org" , "david@kernel.org" , "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" , "shuah@kernel.org" , "riel@surriel.com" , "ryan.roberts@arm.com" , "jgross@suse.com" , "yu-cheng.yu@intel.com" , "kas@kernel.org" , "coxu@redhat.com" , "kevin.brodsky@arm.com" , "ackerleytng@google.com" , "maobibo@loongson.cn" , "prsampat@amd.com" , "mlevitsk@redhat.com" , "jmattson@google.com" , "jthoughton@google.com" , "agordeev@linux.ibm.com" , "alex@ghiti.fr" , "aou@eecs.berkeley.edu" , "borntraeger@linux.ibm.com" , "chenhuacai@kernel.org" , "dev.jain@arm.com" , "gor@linux.ibm.com" , "hca@linux.ibm.com" , "Jonathan.Cameron@huawei.com" , "palmer@dabbelt.com" , "pjw@kernel.org" , "shijie@os.amperecomputing.com" , "svens@linux.ibm.com" , "thuth@redhat.com" , "wyihan@google.com" , "yang@os.amperecomputing.com" , "vannapurve@google.com" , "jackmanb@google.com" , "aneesh.kumar@kernel.org" , "patrick.roy@linux.dev" , "Thomson, Jack" , "Itazuri, Takahiro" , "Manwaring, Derek" , "Cali, Marco" , "Kalyazin, Nikita" Subject: [PATCH v9 08/13] KVM: selftests: load elf via bounce buffer Thread-Topic: [PATCH v9 08/13] KVM: selftests: load elf via bounce buffer Thread-Index: AQHchVw3daaZpEULYUqipVucRFdzxQ== Date: Wed, 14 Jan 2026 13:46:43 +0000 Message-ID: <20260114134510.1835-9-kalyazin@amazon.com> References: <20260114134510.1835-1-kalyazin@amazon.com> In-Reply-To: <20260114134510.1835-1-kalyazin@amazon.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [172.19.103.116] MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260114_054706_722223_935D2D41 X-CRM114-Status: GOOD ( 11.72 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org From: Patrick Roy If guest memory is backed using a VMA that does not allow GUP (e.g. a userspace mapping of guest_memfd when the fd was allocated using GUEST_MEMFD_FLAG_NO_DIRECT_MAP), then directly loading the test ELF binary into it via read(2) potentially does not work. To nevertheless support loading binaries in this cases, do the read(2) syscall using a bounce buffer, and then memcpy from the bounce buffer into guest memory. Signed-off-by: Patrick Roy Signed-off-by: Nikita Kalyazin --- .../testing/selftests/kvm/include/test_util.h | 1 + tools/testing/selftests/kvm/lib/elf.c | 8 +++---- tools/testing/selftests/kvm/lib/io.c | 23 +++++++++++++++++++ 3 files changed, 28 insertions(+), 4 deletions(-) diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h index b4872ba8ed12..8140e59b59e5 100644 --- a/tools/testing/selftests/kvm/include/test_util.h +++ b/tools/testing/selftests/kvm/include/test_util.h @@ -48,6 +48,7 @@ do { \ ssize_t test_write(int fd, const void *buf, size_t count); ssize_t test_read(int fd, void *buf, size_t count); +ssize_t test_read_bounce(int fd, void *buf, size_t count); int test_seq_read(const char *path, char **bufp, size_t *sizep); void __printf(5, 6) test_assert(bool exp, const char *exp_str, diff --git a/tools/testing/selftests/kvm/lib/elf.c b/tools/testing/selftests/kvm/lib/elf.c index f34d926d9735..e829fbe0a11e 100644 --- a/tools/testing/selftests/kvm/lib/elf.c +++ b/tools/testing/selftests/kvm/lib/elf.c @@ -31,7 +31,7 @@ static void elfhdr_get(const char *filename, Elf64_Ehdr *hdrp) * the real size of the ELF header. */ unsigned char ident[EI_NIDENT]; - test_read(fd, ident, sizeof(ident)); + test_read_bounce(fd, ident, sizeof(ident)); TEST_ASSERT((ident[EI_MAG0] == ELFMAG0) && (ident[EI_MAG1] == ELFMAG1) && (ident[EI_MAG2] == ELFMAG2) && (ident[EI_MAG3] == ELFMAG3), "ELF MAGIC Mismatch,\n" @@ -79,7 +79,7 @@ static void elfhdr_get(const char *filename, Elf64_Ehdr *hdrp) offset_rv = lseek(fd, 0, SEEK_SET); TEST_ASSERT(offset_rv == 0, "Seek to ELF header failed,\n" " rv: %zi expected: %i", offset_rv, 0); - test_read(fd, hdrp, sizeof(*hdrp)); + test_read_bounce(fd, hdrp, sizeof(*hdrp)); TEST_ASSERT(hdrp->e_phentsize == sizeof(Elf64_Phdr), "Unexpected physical header size,\n" " hdrp->e_phentsize: %x\n" @@ -146,7 +146,7 @@ void kvm_vm_elf_load(struct kvm_vm *vm, const char *filename) /* Read in the program header. */ Elf64_Phdr phdr; - test_read(fd, &phdr, sizeof(phdr)); + test_read_bounce(fd, &phdr, sizeof(phdr)); /* Skip if this header doesn't describe a loadable segment. */ if (phdr.p_type != PT_LOAD) @@ -187,7 +187,7 @@ void kvm_vm_elf_load(struct kvm_vm *vm, const char *filename) " expected: 0x%jx", n1, errno, (intmax_t) offset_rv, (intmax_t) phdr.p_offset); - test_read(fd, addr_gva2hva(vm, phdr.p_vaddr), + test_read_bounce(fd, addr_gva2hva(vm, phdr.p_vaddr), phdr.p_filesz); } } diff --git a/tools/testing/selftests/kvm/lib/io.c b/tools/testing/selftests/kvm/lib/io.c index fedb2a741f0b..74419becc8bc 100644 --- a/tools/testing/selftests/kvm/lib/io.c +++ b/tools/testing/selftests/kvm/lib/io.c @@ -155,3 +155,26 @@ ssize_t test_read(int fd, void *buf, size_t count) return num_read; } + +/* Test read via intermediary buffer + * + * Same as test_read, except read(2)s happen into a bounce buffer that is memcpy'd + * to buf. For use with buffers that cannot be GUP'd (e.g. guest_memfd VMAs if + * guest_memfd was created with GUEST_MEMFD_FLAG_NO_DIRECT_MAP). + */ +ssize_t test_read_bounce(int fd, void *buf, size_t count) +{ + void *bounce_buffer; + ssize_t num_read; + + TEST_ASSERT(count >= 0, "Unexpected count, count: %li", count); + + bounce_buffer = malloc(count); + TEST_ASSERT(bounce_buffer != NULL, "Failed to allocate bounce buffer"); + + num_read = test_read(fd, bounce_buffer, count); + memcpy(buf, bounce_buffer, num_read); + free(bounce_buffer); + + return num_read; +} -- 2.50.1 _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv