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 X-Spam-Level: X-Spam-Status: No, score=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84033C64E7B for ; Tue, 1 Dec 2020 15:00:52 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id D21092084C for ; Tue, 1 Dec 2020 15:00:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D21092084C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 59E5B4C282; Tue, 1 Dec 2020 10:00:51 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id vvJtpwZl0TbJ; Tue, 1 Dec 2020 10:00:50 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id E7F2E4C287; Tue, 1 Dec 2020 10:00:48 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id ECD974C270 for ; Tue, 1 Dec 2020 10:00:47 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id gP6GL2e1fB7P for ; Tue, 1 Dec 2020 10:00:46 -0500 (EST) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 446C24C26F for ; Tue, 1 Dec 2020 10:00:45 -0500 (EST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D0E9D30E; Tue, 1 Dec 2020 07:00:44 -0800 (PST) Received: from monolith.localdoman (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E33A63F575; Tue, 1 Dec 2020 07:00:43 -0800 (PST) From: Alexandru Elisei To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, maz@kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com Subject: [PATCH 3/5] KVM: arm64: Move double-checked lock to kvm_vgic_map_resources() Date: Tue, 1 Dec 2020 15:01:55 +0000 Message-Id: <20201201150157.223625-4-alexandru.elisei@arm.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201201150157.223625-1-alexandru.elisei@arm.com> References: <20201201150157.223625-1-alexandru.elisei@arm.com> MIME-Version: 1.0 X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu kvm_vgic_map_resources() is called when a VCPU if first run and it maps all the VGIC MMIO regions. To prevent double-initialization, the VGIC uses the ready variable to keep track of the state of resources and the global KVM mutex to protect against concurrent accesses. After the lock is taken, the variable is checked again in case another VCPU took the lock between the current VCPU reading ready equals false and taking the lock. The double-checked lock pattern is spread across four different functions: in kvm_vcpu_first_run_init(), in kvm_vgic_map_resource() and in vgic_{v2,v3}_map_resources(), which makes it hard to reason about and introduces minor code duplication. Consolidate the checks in kvm_vgic_map_resources(), where the lock is taken. No functional change intended. Signed-off-by: Alexandru Elisei --- arch/arm64/kvm/arm.c | 8 +++----- arch/arm64/kvm/vgic/vgic-init.c | 6 ++++++ arch/arm64/kvm/vgic/vgic-v2.c | 3 --- arch/arm64/kvm/vgic/vgic-v3.c | 3 --- 4 files changed, 9 insertions(+), 11 deletions(-) diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 9d69d2bf6943..65a5e89f5133 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -530,11 +530,9 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu) * Map the VGIC hardware resources before running a vcpu the * first time on this VM. */ - if (unlikely(!vgic_ready(kvm))) { - ret = kvm_vgic_map_resources(kvm); - if (ret) - return ret; - } + ret = kvm_vgic_map_resources(kvm); + if (ret) + return ret; } else { /* * Tell the rest of the code that there are userspace irqchip diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c index 32e32d67a127..a2f4d1c85f00 100644 --- a/arch/arm64/kvm/vgic/vgic-init.c +++ b/arch/arm64/kvm/vgic/vgic-init.c @@ -428,7 +428,13 @@ int kvm_vgic_map_resources(struct kvm *kvm) struct vgic_dist *dist = &kvm->arch.vgic; int ret = 0; + if (likely(vgic_ready(kvm))) + return 0; + mutex_lock(&kvm->lock); + if (vgic_ready(kvm)) + goto out; + if (!irqchip_in_kernel(kvm)) goto out; diff --git a/arch/arm64/kvm/vgic/vgic-v2.c b/arch/arm64/kvm/vgic/vgic-v2.c index ebf53a4e1296..7f38c1a93639 100644 --- a/arch/arm64/kvm/vgic/vgic-v2.c +++ b/arch/arm64/kvm/vgic/vgic-v2.c @@ -306,9 +306,6 @@ int vgic_v2_map_resources(struct kvm *kvm) struct vgic_dist *dist = &kvm->arch.vgic; int ret = 0; - if (vgic_ready(kvm)) - goto out; - if (IS_VGIC_ADDR_UNDEF(dist->vgic_dist_base) || IS_VGIC_ADDR_UNDEF(dist->vgic_cpu_base)) { kvm_err("Need to set vgic cpu and dist addresses first\n"); diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c index 9cdf39a94a63..35029c5cb0f1 100644 --- a/arch/arm64/kvm/vgic/vgic-v3.c +++ b/arch/arm64/kvm/vgic/vgic-v3.c @@ -500,9 +500,6 @@ int vgic_v3_map_resources(struct kvm *kvm) int ret = 0; int c; - if (vgic_ready(kvm)) - goto out; - kvm_for_each_vcpu(c, vcpu, kvm) { struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu; -- 2.29.2 _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm 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 X-Spam-Level: X-Spam-Status: No, score=-18.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 61CA1C64E7B for ; Tue, 1 Dec 2020 15:02:12 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E5F1E20691 for ; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org kvm_vgic_map_resources() is called when a VCPU if first run and it maps all the VGIC MMIO regions. To prevent double-initialization, the VGIC uses the ready variable to keep track of the state of resources and the global KVM mutex to protect against concurrent accesses. After the lock is taken, the variable is checked again in case another VCPU took the lock between the current VCPU reading ready equals false and taking the lock. The double-checked lock pattern is spread across four different functions: in kvm_vcpu_first_run_init(), in kvm_vgic_map_resource() and in vgic_{v2,v3}_map_resources(), which makes it hard to reason about and introduces minor code duplication. Consolidate the checks in kvm_vgic_map_resources(), where the lock is taken. No functional change intended. Signed-off-by: Alexandru Elisei --- arch/arm64/kvm/arm.c | 8 +++----- arch/arm64/kvm/vgic/vgic-init.c | 6 ++++++ arch/arm64/kvm/vgic/vgic-v2.c | 3 --- arch/arm64/kvm/vgic/vgic-v3.c | 3 --- 4 files changed, 9 insertions(+), 11 deletions(-) diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 9d69d2bf6943..65a5e89f5133 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -530,11 +530,9 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu) * Map the VGIC hardware resources before running a vcpu the * first time on this VM. */ - if (unlikely(!vgic_ready(kvm))) { - ret = kvm_vgic_map_resources(kvm); - if (ret) - return ret; - } + ret = kvm_vgic_map_resources(kvm); + if (ret) + return ret; } else { /* * Tell the rest of the code that there are userspace irqchip diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c index 32e32d67a127..a2f4d1c85f00 100644 --- a/arch/arm64/kvm/vgic/vgic-init.c +++ b/arch/arm64/kvm/vgic/vgic-init.c @@ -428,7 +428,13 @@ int kvm_vgic_map_resources(struct kvm *kvm) struct vgic_dist *dist = &kvm->arch.vgic; int ret = 0; + if (likely(vgic_ready(kvm))) + return 0; + mutex_lock(&kvm->lock); + if (vgic_ready(kvm)) + goto out; + if (!irqchip_in_kernel(kvm)) goto out; diff --git a/arch/arm64/kvm/vgic/vgic-v2.c b/arch/arm64/kvm/vgic/vgic-v2.c index ebf53a4e1296..7f38c1a93639 100644 --- a/arch/arm64/kvm/vgic/vgic-v2.c +++ b/arch/arm64/kvm/vgic/vgic-v2.c @@ -306,9 +306,6 @@ int vgic_v2_map_resources(struct kvm *kvm) struct vgic_dist *dist = &kvm->arch.vgic; int ret = 0; - if (vgic_ready(kvm)) - goto out; - if (IS_VGIC_ADDR_UNDEF(dist->vgic_dist_base) || IS_VGIC_ADDR_UNDEF(dist->vgic_cpu_base)) { kvm_err("Need to set vgic cpu and dist addresses first\n"); diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c index 9cdf39a94a63..35029c5cb0f1 100644 --- a/arch/arm64/kvm/vgic/vgic-v3.c +++ b/arch/arm64/kvm/vgic/vgic-v3.c @@ -500,9 +500,6 @@ int vgic_v3_map_resources(struct kvm *kvm) int ret = 0; int c; - if (vgic_ready(kvm)) - goto out; - kvm_for_each_vcpu(c, vcpu, kvm) { struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu; -- 2.29.2 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel