From nobody Fri Oct 3 16:38:40 2025 Received: from fra-out-004.esa.eu-central-1.outbound.mail-perimeter.amazon.com (fra-out-004.esa.eu-central-1.outbound.mail-perimeter.amazon.com [3.74.81.189]) (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 BE6382F99A9; Thu, 28 Aug 2025 09:39:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=3.74.81.189 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756373983; cv=none; b=VEMRSjxoE3Y8ggowNMCijrA8NeBtfo5F9jM0bmufQL1cL1kvUW7J6YMKHYNu9ZRF+ShhzjpQb+ao/C8iMyJJeRMTuGw+iNLk0H5QIjvZ5bviaWziBaxpH5q+PB1+OVO+ZuMaYF7Mo2c6amNQvhrv7s1TYgO4XZmBiA0VWmk5Q5k= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756373983; c=relaxed/simple; bh=DmIagpWgO2oSc2B+bRyWsRmMy0e5IBuFMLQtHeyV8bs=; h=From:To:CC:Subject:Date:Message-ID:References:In-Reply-To: Content-Type:MIME-Version; b=A0F9gNejmlaiBAkqkYApaXOBtpd6DQbugfmDBMXZ3P1CY1ZUXBWo3QpohfQkWaE5WiJy2jlh8KZ0OR5iXishRmo4SRllvQCZxmwqlFR9XtvVNlSof9/O1gILvxnXZEYmG/8+Ydp2f3FZAwQO8JCLhqs7rHr4tl2pSwDz70GgP5E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.co.uk; spf=pass smtp.mailfrom=amazon.co.uk; dkim=pass (2048-bit key) header.d=amazon.co.uk header.i=@amazon.co.uk header.b=VuSj67Tr; arc=none smtp.client-ip=3.74.81.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.co.uk Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.co.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amazon.co.uk header.i=@amazon.co.uk header.b="VuSj67Tr" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.co.uk; i=@amazon.co.uk; q=dns/txt; s=amazoncorp2; t=1756373981; x=1787909981; h=from:to:cc:subject:date:message-id:references: in-reply-to:content-transfer-encoding:mime-version; bh=KTZ/VOJbbCjyGaq9AddgILCkPAHpmVIUuRAnTMPHRJE=; b=VuSj67TrhmSMkQ9sCteXvivAEan0RfyGx+MoAT2xEFmKuWrKzmiOOtW3 e7g8++Igomp0NX3yE/md02oyhPLUSHj+P86osNfkHo6A91p16QD870KAM m8bNMz3hpXyatvBUsfpW97f9zPkgGOVe4+EJvV+WiE9hyi7V0EpfvwL4q 6oL+XWRy8NQCGUrCM3Egv/p8tNO0/iX9aTj6FP34vq53/tFeFsJKNzKyq KOTemWne11Jl4fSx5mNWGiwg/san+MMjfX6GiRoAcIrXsVnjI2WSqxLGj sh5WOSSklF9NJnpmYwZYbt8mMwwz4ZoBSW829JV09oSqu8Tym9sQP4ptn A==; X-CSE-ConnectionGUID: u9bjUTy6TKSekmiuaprUTA== X-CSE-MsgGUID: 8rDPM4y3Rdeb1tmBEIF3eA== X-IronPort-AV: E=Sophos;i="6.18,214,1751241600"; d="scan'208";a="1303834" Received: from ip-10-6-6-97.eu-central-1.compute.internal (HELO smtpout.naws.eu-central-1.prod.farcaster.email.amazon.dev) ([10.6.6.97]) by internal-fra-out-004.esa.eu-central-1.outbound.mail-perimeter.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Aug 2025 09:39:27 +0000 Received: from EX19MTAEUA001.ant.amazon.com [54.240.197.233:20173] by smtpin.naws.eu-central-1.prod.farcaster.email.amazon.dev [10.0.43.161:2525] with esmtp (Farcaster) id f5543d0c-1ca4-4856-a828-4fcfa81cf84a; Thu, 28 Aug 2025 09:39:27 +0000 (UTC) X-Farcaster-Flow-ID: f5543d0c-1ca4-4856-a828-4fcfa81cf84a Received: from EX19D015EUB002.ant.amazon.com (10.252.51.123) by EX19MTAEUA001.ant.amazon.com (10.252.50.223) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.17; Thu, 28 Aug 2025 09:39:24 +0000 Received: from EX19D015EUB004.ant.amazon.com (10.252.51.13) by EX19D015EUB002.ant.amazon.com (10.252.51.123) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.17; Thu, 28 Aug 2025 09:39:24 +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 15.02.2562.017; Thu, 28 Aug 2025 09:39:24 +0000 From: "Roy, Patrick" To: "david@redhat.com" , "seanjc@google.com" CC: "Roy, Patrick" , "tabba@google.com" , "ackerleytng@google.com" , "pbonzini@redhat.com" , "kvm@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "kvmarm@lists.linux.dev" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "rppt@kernel.org" , "will@kernel.org" , "vbabka@suse.cz" , "Cali, Marco" , "Kalyazin, Nikita" , "Thomson, Jack" , "Manwaring, Derek" Subject: [PATCH v5 06/12] KVM: selftests: load elf via bounce buffer Thread-Topic: [PATCH v5 06/12] KVM: selftests: load elf via bounce buffer Thread-Index: AQHcF/+j1UnlcgO4tUakgBJ2Lj709w== Date: Thu, 28 Aug 2025 09:39:24 +0000 Message-ID: <20250828093902.2719-7-roypat@amazon.co.uk> References: <20250828093902.2719-1-roypat@amazon.co.uk> In-Reply-To: <20250828093902.2719-1-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" 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 KVM_GMEM_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 --- .../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/testin= g/selftests/kvm/include/test_util.h index c6ef895fbd9a..0409b7b96c94 100644 --- a/tools/testing/selftests/kvm/include/test_util.h +++ b/tools/testing/selftests/kvm/include/test_util.h @@ -46,6 +46,7 @@ do { \ =20 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); =20 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/selftest= s/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] =3D=3D ELFMAG0) && (ident[EI_MAG1] =3D=3D ELF= MAG1) && (ident[EI_MAG2] =3D=3D ELFMAG2) && (ident[EI_MAG3] =3D=3D ELFMAG3), "ELF MAGIC Mismatch,\n" @@ -79,7 +79,7 @@ static void elfhdr_get(const char *filename, Elf64_Ehdr *= hdrp) offset_rv =3D lseek(fd, 0, SEEK_SET); TEST_ASSERT(offset_rv =3D=3D 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 =3D=3D 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 *fil= ename) =20 /* Read in the program header. */ Elf64_Phdr phdr; - test_read(fd, &phdr, sizeof(phdr)); + test_read_bounce(fd, &phdr, sizeof(phdr)); =20 /* Skip if this header doesn't describe a loadable segment. */ if (phdr.p_type !=3D PT_LOAD) @@ -187,7 +187,7 @@ void kvm_vm_elf_load(struct kvm_vm *vm, const char *fil= ename) " 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) =20 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 VMA= s 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 >=3D 0, "Unexpected count, count: %li", count); + + bounce_buffer =3D malloc(count); + TEST_ASSERT(bounce_buffer !=3D NULL, "Failed to allocate bounce buffer"); + + num_read =3D test_read(fd, bounce_buffer, count); + memcpy(buf, bounce_buffer, num_read); + free(bounce_buffer); + + return num_read; +} --=20 2.50.1