From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A5DDAC433F5 for ; Tue, 5 Apr 2022 13:07:02 +0000 (UTC) Received: from localhost ([::1]:56462 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nbith-00021B-MA for qemu-devel@archiver.kernel.org; Tue, 05 Apr 2022 09:07:01 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43040) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nbirh-0000R0-EX for qemu-devel@nongnu.org; Tue, 05 Apr 2022 09:04:57 -0400 Received: from mail-oa1-x2e.google.com ([2001:4860:4864:20::2e]:46460) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1nbirf-0003xY-Gd for qemu-devel@nongnu.org; Tue, 05 Apr 2022 09:04:57 -0400 Received: by mail-oa1-x2e.google.com with SMTP id 586e51a60fabf-d39f741ba0so14245504fac.13 for ; Tue, 05 Apr 2022 06:04:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=akBslgGtD7yVObalqIwNNaUBrshy9tWJ6X+w0+2xKLE=; b=Z7XnhHLs2FV572tRsmv7dWZtlFFPkr0yqHr7R11ZM4HUOXLaqXZ3/vRaMUaFGcFPI1 jN/RGJXFmdxJUsihnfxP09UCHDWWWklfg+aiMX4MGoHEy705KtsdcVT2z/RbvuzwFiO3 anPwXiJ4sOZ43fE+ZOZ37KAvU7xyqcmSoC2CSC7tYkp1qwcyMLd2ulN7qmgbwN4JFr17 fUWixE0KBh5ToTCaXqNJexCe/sLhmFDTqBKlyza3zt2BbSlwW0rzSZNc/KL7c8BAK4tu qRU5cfOc7G10SmkZ2GTBCQ7Ih2biCTdb3kp7aZqdsUyGFwA46ienJ6w2R0d2SQs+Bmir eGDQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=akBslgGtD7yVObalqIwNNaUBrshy9tWJ6X+w0+2xKLE=; b=iV4CCxXpa7CRuASMsmdIbxP3t3tMbxuHgr8u34fR1ikO6YrW6Vqobq41idLUO+i6+w CB12wkQ2lroDnCh7OoFnmoCcFWcTWrvuywaTxzfafJB4V9LYhvgZxWTGxokb4Rd0ERpR UnLi1ns0ebYx/N73HxrzQlqCi1OFpxjEtufteV5rfMyD0BSr1lBMJzdtun9w+gL8BlRw AANhFQ9X0CulZsEM6INDDLrouurRpPxE6EfEBSzDqzj8FsGxI2baAPlIANQLBpDJjFlQ FbRyTyWMavA5D2NjKPzrBP1HcBKGb6PuVPxOVPGldXiRTx4dUBzfAejWZPCE3U5Cg13U Mc+g== X-Gm-Message-State: AOAM530bhvSFDxRDQfYsqYk6t6oEMjOGphJ8SaOSC02EdQ9k/IbpwOc1 jrscRNI41ukCOrWF+gqQl3MYPzvRNQg= X-Google-Smtp-Source: ABdhPJxnpaOawuqQq+jA3fyZut6iHTQbR3Ejcx8PM8TnaWul2aktwDs+X1yyVXAhy9c2Z1N+ePujCw== X-Received: by 2002:a05:6870:c20f:b0:e2:434:c3e1 with SMTP id z15-20020a056870c20f00b000e20434c3e1mr1509442oae.266.1649163894113; Tue, 05 Apr 2022 06:04:54 -0700 (PDT) Received: from rekt.ibmmodules.com ([2804:431:c7c6:abe8:ed:2c78:ab0c:7946]) by smtp.gmail.com with ESMTPSA id 60-20020a9d0642000000b005b22a82458csm5658134otn.55.2022.04.05.06.04.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Apr 2022 06:04:53 -0700 (PDT) From: Daniel Henrique Barboza To: qemu-devel@nongnu.org Subject: [RFC PATCH 1/1] kvm-all.c: hint Valgrind that kvm_get_one_reg() inits memory Date: Tue, 5 Apr 2022 10:04:39 -0300 Message-Id: <20220405130439.44253-2-danielhb413@gmail.com> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220405130439.44253-1-danielhb413@gmail.com> References: <20220405130439.44253-1-danielhb413@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2001:4860:4864:20::2e; envelope-from=danielhb413@gmail.com; helo=mail-oa1-x2e.google.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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: Paolo Bonzini , Daniel Henrique Barboza , david@gibson.dropbear.id.au Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" There is a lot of Valgrind warnings about conditional jump depending on unintialized values like this one (taken from a pSeries guest): Conditional jump or move depends on uninitialised value(s) at 0xB011DC: kvmppc_enable_cap_large_decr (kvm.c:2544) by 0x92F28F: cap_large_decr_cpu_apply (spapr_caps.c:523) by 0x930C37: spapr_caps_cpu_apply (spapr_caps.c:921) by 0x955D3B: spapr_reset_vcpu (spapr_cpu_core.c:73) (...) Uninitialised value was created by a stack allocation at 0xB01150: kvmppc_enable_cap_large_decr (kvm.c:2538) In this case, the alleged unintialized value is the 'lpcr' variable that is written by kvm_get_one_reg() and then used in an if clause: int kvmppc_enable_cap_large_decr(PowerPCCPU *cpu, int enable) { CPUState *cs = CPU(cpu); uint64_t lpcr; kvm_get_one_reg(cs, KVM_REG_PPC_LPCR_64, &lpcr); /* Do we need to modify the LPCR? */ if (!!(lpcr & LPCR_LD) != !!enable) { <---- Valgrind warns here (...) A quick fix is to init the variable that kvm_get_one_reg() is going to write ('lpcr' in the example above). Another idea is to convince Valgrind that kvm_get_one_reg() inits the 'void *target' memory in case the ioctl() is successful. This will put some boilerplate in the function but it will bring benefit for its other callers. This patch uses the memcheck VALGRING_MAKE_MEM_DEFINED() to mark the 'target' variable as initialized if the ioctl is successful. Cc: Paolo Bonzini Signed-off-by: Daniel Henrique Barboza --- accel/kvm/kvm-all.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index 5f1377ca04..d9acba23c7 100644 --- a/accel/kvm/kvm-all.c +++ b/accel/kvm/kvm-all.c @@ -53,6 +53,10 @@ #include #endif +#ifdef CONFIG_VALGRIND_H +#include +#endif + /* KVM uses PAGE_SIZE in its definition of KVM_COALESCED_MMIO_MAX. We * need to use the real host PAGE_SIZE, as that's what KVM will use. */ @@ -3504,6 +3508,19 @@ int kvm_get_one_reg(CPUState *cs, uint64_t id, void *target) if (r) { trace_kvm_failed_reg_get(id, strerror(-r)); } + +#ifdef CONFIG_VALGRIND_H + if (r == 0) { + switch (id & KVM_REG_SIZE_MASK) { + case KVM_REG_SIZE_U32: + VALGRIND_MAKE_MEM_DEFINED(target, sizeof(uint32_t)); + break; + case KVM_REG_SIZE_U64: + VALGRIND_MAKE_MEM_DEFINED(target, sizeof(uint64_t)); + break; + } + } +#endif return r; } -- 2.35.1