From nobody Mon Feb 9 07:26:19 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=fail; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1647881249373189.1227704740994; Mon, 21 Mar 2022 09:47:29 -0700 (PDT) Received: from localhost ([::1]:56764 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nWLBn-0004nJ-VI for importer@patchew.org; Mon, 21 Mar 2022 12:47:27 -0400 Received: from eggs.gnu.org ([209.51.188.92]:37390) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nWL9Y-0002PJ-8t for qemu-devel@nongnu.org; Mon, 21 Mar 2022 12:45:08 -0400 Received: from [2a00:1450:4864:20::52c] (port=35614 helo=mail-ed1-x52c.google.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1nWL9W-00081N-FU for qemu-devel@nongnu.org; Mon, 21 Mar 2022 12:45:07 -0400 Received: by mail-ed1-x52c.google.com with SMTP id k10so4841634edj.2 for ; Mon, 21 Mar 2022 09:45:06 -0700 (PDT) Received: from avogadro.redhat.com ([2001:b07:6468:f312:63a7:c72e:ea0e:6045]) by smtp.gmail.com with ESMTPSA id a102-20020a509eef000000b0041614c8f79asm7949352edf.88.2022.03.21.09.45.04 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Mar 2022 09:45:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:from:to:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=efi8DSRTf2i20NY52YUXz0KrEVCIILq2P4XhBCv2IZg=; b=Z7heLaZ7whcQFy5E86/fOscN6/fuPsbg5WOJ2eeXLP3ADu5hYFoTL2M5uSD99EjKpr iFYNVeY0rh1AfJyyLFB+8XqZKyAOZU7oPO9N9WpXcZWoR+fbOAfMdrY07i5CMi0UJdeb OgRiFoMMeDpfM6oY52ik48xVBxAPeZBd+j90v7SgExOzOtWRPD+Cnnbi1E7VOsxiAsgP DOZBmX4YO7fFu2z7sUc4P3lvNmrxiFGVyFpKRQCQvDLM7Vq0enRURQDXdkH/Vl42rWQW gdCN9sImFyhhgDX2uhMcJY98Yu4V6Amv8HGv5eq8TyA8TUbLUxbryQNz2x51dwNs+PKP vyFg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:from:to:subject:date:message-id :in-reply-to:references:mime-version:content-transfer-encoding; bh=efi8DSRTf2i20NY52YUXz0KrEVCIILq2P4XhBCv2IZg=; b=VgbbKgAvBIxR3Gm2C1CateHo7Oi08JVH+e+b0BTF/SEMCZ0mlSnkIcS1T74jxl1qrl TmK4MuQYoJA5nz0aDfeT0T3mHoyVOFBbtvTVXrwE4VwntkhydeLO4chet3IC8x4gUsL6 qRd2G1sNc97E3Iv7rk8yOMwxmI9v2oPV+t/rvPRt0x4KcVn6fe7L5hEdHW01XofpxgFt VI4dUi+rq0Pngy/lKYbrUIJ3y9UFvFxpId48xU6ScNyZh1cWQf5SoHeOmYDbGyajB44t cjhN5hDYJ7R9/+DUbMbSmNoGLlcxHU0zneUYxSBUF+UStzj9mV/uaAitkGHbCaBfdhVT Yovw== X-Gm-Message-State: AOAM530BDyQXnpCMgq91aufDGeo3p7DFqr2HBPQ5ugeUXUOc8HxZvr0z 63MmxaueefVuME+S253TDfyz3c0Q+qc= X-Google-Smtp-Source: ABdhPJwWKREyySZf771JABKj0wk//ydliDWWNVluKijobp/S/9c2c4u1su8j9NsaVq0BJ9+M8hrHrg== X-Received: by 2002:a05:6402:17dc:b0:418:efa5:f445 with SMTP id s28-20020a05640217dc00b00418efa5f445mr23805286edy.125.1647881105154; Mon, 21 Mar 2022 09:45:05 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PULL 1/2] target/i386: kvm: do not access uninitialized variable on older kernels Date: Mon, 21 Mar 2022 17:45:01 +0100 Message-Id: <20220321164502.201160-2-pbonzini@redhat.com> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220321164502.201160-1-pbonzini@redhat.com> References: <20220321164502.201160-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Host-Lookup-Failed: Reverse DNS lookup failed for 2a00:1450:4864:20::52c (failed) Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2a00:1450:4864:20::52c; envelope-from=paolo.bonzini@gmail.com; helo=mail-ed1-x52c.google.com X-Spam_score_int: 0 X-Spam_score: -0.1 X-Spam_bar: / X-Spam_report: (-0.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FORGED_FROMDOMAIN=0.249, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.249, PDS_HP_HELO_NORDNS=0.659, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZM-MESSAGEID: 1647881250479100001 Content-Type: text/plain; charset="utf-8" KVM support for AMX includes a new system attribute, KVM_X86_XCOMP_GUEST_SU= PP. Commit 19db68ca68 ("x86: Grant AMX permission for guest", 2022-03-15) howev= er did not fully consider the behavior on older kernels. First, it warns too aggressively. Second, it invokes the KVM_GET_DEVICE_ATTR ioctl unconditionally and then uses the "bitmask" variable, which remains uninitialized if the ioctl fails. Third, kvm_ioctl returns -errno rather than -1 on errors. While at it, explain why the ioctl is needed and KVM_GET_SUPPORTED_CPUID is not enough. Signed-off-by: Paolo Bonzini --- target/i386/kvm/kvm.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index ef2c68a6f4..06901c2a43 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -411,6 +411,12 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uin= t32_t function, } } else if (function =3D=3D 0xd && index =3D=3D 0 && (reg =3D=3D R_EAX || reg =3D=3D R_EDX)) { + /* + * The value returned by KVM_GET_SUPPORTED_CPUID does not include + * features that still have to be enabled with the arch_prctl + * system call. QEMU needs the full value, which is retrieved + * with KVM_GET_DEVICE_ATTR. + */ struct kvm_device_attr attr =3D { .group =3D 0, .attr =3D KVM_X86_XCOMP_GUEST_SUPP, @@ -419,13 +425,16 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, ui= nt32_t function, =20 bool sys_attr =3D kvm_check_extension(s, KVM_CAP_SYS_ATTRIBUTES); if (!sys_attr) { - warn_report("cannot get sys attribute capabilities %d", sys_at= tr); + return ret; } =20 int rc =3D kvm_ioctl(s, KVM_GET_DEVICE_ATTR, &attr); - if (rc =3D=3D -1 && (errno =3D=3D ENXIO || errno =3D=3D EINVAL)) { - warn_report("KVM_GET_DEVICE_ATTR(0, KVM_X86_XCOMP_GUEST_SUPP) " - "error: %d", rc); + if (rc < 0) { + if (rc !=3D -ENXIO) { + warn_report("KVM_GET_DEVICE_ATTR(0, KVM_X86_XCOMP_GUEST_SU= PP) " + "error: %d", rc); + } + return ret; } ret =3D (reg =3D=3D R_EAX) ? bitmask : bitmask >> 32; } else if (function =3D=3D 0x80000001 && reg =3D=3D R_ECX) { --=20 2.35.1 From nobody Mon Feb 9 07:26:19 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; 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charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Host-Lookup-Failed: Reverse DNS lookup failed for 2a00:1450:4864:20::52e (failed) Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2a00:1450:4864:20::52e; envelope-from=paolo.bonzini@gmail.com; helo=mail-ed1-x52e.google.com X-Spam_score_int: 0 X-Spam_score: -0.1 X-Spam_bar: / X-Spam_report: (-0.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FORGED_FROMDOMAIN=0.249, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.249, PDS_HP_HELO_NORDNS=0.659, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZM-MESSAGEID: 1647881375855100001 Be more explicit that the loop must roll at least once. Avoids the following warning: FAILED: libqemu-x86_64-softmmu.fa.p/hw_i386_amd_iommu.c.o In function 'pte_get_page_mask', inlined from 'amdvi_page_walk' at hw/i386/amd_iommu.c:945:25, inlined from 'amdvi_do_translate' at hw/i386/amd_iommu.c:989:5, inlined from 'amdvi_translate' at hw/i386/amd_iommu.c:1038:5: hw/i386/amd_iommu.c:877:38: error: 'oldlevel' may be used uninitialized [= -Werror=3Dmaybe-uninitialized] 877 | return ~((1UL << ((oldlevel * 9) + 3)) - 1); | ~~~~~~~~~~~~~~~~^~~~ hw/i386/amd_iommu.c: In function 'amdvi_translate': hw/i386/amd_iommu.c:906:41: note: 'oldlevel' was declared here 906 | unsigned level, present, pte_perms, oldlevel; | ^~~~~~~~ cc1: all warnings being treated as errors Having: $ gcc --version gcc (Debian 12-20220313-1) 12.0.1 20220314 (experimental) Reported-by: Philippe Mathieu-Daud=C3=A9 Signed-off-by: Paolo Bonzini --- hw/i386/amd_iommu.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/hw/i386/amd_iommu.c b/hw/i386/amd_iommu.c index 4d13d8e697..6986ad3b87 100644 --- a/hw/i386/amd_iommu.c +++ b/hw/i386/amd_iommu.c @@ -913,7 +913,7 @@ static void amdvi_page_walk(AMDVIAddressSpace *as, uint= 64_t *dte, } =20 /* we are at the leaf page table or page table encodes a huge page= */ - while (level > 0) { + do { pte_perms =3D amdvi_get_perms(pte); present =3D pte & 1; if (!present || perms !=3D (perms & pte_perms)) { @@ -932,10 +932,7 @@ static void amdvi_page_walk(AMDVIAddressSpace *as, uin= t64_t *dte, } oldlevel =3D level; level =3D get_pte_translation_mode(pte); - if (level =3D=3D 0x7) { - break; - } - } + } while (level > 0 && level < 7); =20 if (level =3D=3D 0x7) { page_mask =3D pte_override_page_mask(pte); --=20 2.35.1