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=-12.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 258C5C43465 for ; Mon, 21 Sep 2020 15:46:32 +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 8742420EDD for ; Mon, 21 Sep 2020 15:46:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="SVci5XBX" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8742420EDD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Z0d3N/7MS2jlkhZoGZFjwkYCLxhqy1+aSo22ToRHfxE=; b=SVci5XBX+SlZ8S2fvAsV5Qjlr sJv6jic0qT0lcsWQjVmZ0RiqL4PdMkfwe47mt0GhwnDKAKDDN4LwjQ9Q367RUtm6VNdD1ybYg20Tm oplnWDp/K4nszxCbNE2AIVasp79p48gQRGqXnwF0/vOizv8h9krf165Bx8BByX+dObSJo7koAWXnw Vh7vUwdBUVk+Lq7jVl2TCVG5qixne5sPNBDeyXG+enOuA0qqy5OpyDFe+eikCLlHz5E+UNKz7ESV3 77zVFcD0/qDeTHeXMpbZCGPEFrt3FgKsbk6niG8FREDYXE22WDaBBEzLS3PTa4jW1muYtqXxj9LKA KmptcDIbg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kKNzq-0003CV-PR; Mon, 21 Sep 2020 15:44:55 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kKNzk-0003AS-5P for linux-arm-kernel@lists.infradead.org; Mon, 21 Sep 2020 15:44:49 +0000 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 A864E147A; Mon, 21 Sep 2020 08:44:46 -0700 (PDT) Received: from [192.168.0.110] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B01013F718; Mon, 21 Sep 2020 08:44:44 -0700 (PDT) Subject: Re: [PATCH v6 5/7] KVM: arm64: pmu: Make overflow handler NMI safe To: Will Deacon References: <20200819133419.526889-1-alexandru.elisei@arm.com> <20200819133419.526889-6-alexandru.elisei@arm.com> <20200921134301.GJ2139@willie-the-truck> From: Alexandru Elisei Message-ID: Date: Mon, 21 Sep 2020 16:45:51 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20200921134301.GJ2139@willie-the-truck> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200921_114448_290215_256F7122 X-CRM114-Status: GOOD ( 27.38 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, sumit.garg@linaro.org, kvm@vger.kernel.org, Julien Thierry , Marc Zyngier , maz@kernel.org, Suzuki K Pouloze , Will Deacon , linux-kernel@vger.kernel.org, swboyd@chromium.org, James Morse , Julien Thierry , catalin.marinas@arm.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; 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 Hi Will, On 9/21/20 2:43 PM, Will Deacon wrote: > On Wed, Aug 19, 2020 at 02:34:17PM +0100, Alexandru Elisei wrote: >> From: Julien Thierry >> >> kvm_vcpu_kick() is not NMI safe. When the overflow handler is called from >> NMI context, defer waking the vcpu to an irq_work queue. >> >> Cc: Julien Thierry >> Cc: Marc Zyngier >> Cc: Will Deacon >> Cc: Mark Rutland >> Cc: Catalin Marinas >> Cc: James Morse >> Cc: Suzuki K Pouloze >> Cc: kvm@vger.kernel.org >> Cc: kvmarm@lists.cs.columbia.edu >> Signed-off-by: Julien Thierry >> Signed-off-by: Alexandru Elisei >> --- >> arch/arm64/kvm/pmu-emul.c | 25 ++++++++++++++++++++++++- >> include/kvm/arm_pmu.h | 1 + >> 2 files changed, 25 insertions(+), 1 deletion(-) > I'd like an Ack from the KVM side on this one, but some minor comments > inline. > >> diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c >> index f0d0312c0a55..30268397ed06 100644 >> --- a/arch/arm64/kvm/pmu-emul.c >> +++ b/arch/arm64/kvm/pmu-emul.c >> @@ -433,6 +433,22 @@ void kvm_pmu_sync_hwstate(struct kvm_vcpu *vcpu) >> kvm_pmu_update_state(vcpu); >> } >> >> +/** >> + * When perf interrupt is an NMI, we cannot safely notify the vcpu corresponding >> + * to the event. >> + * This is why we need a callback to do it once outside of the NMI context. >> + */ >> +static void kvm_pmu_perf_overflow_notify_vcpu(struct irq_work *work) >> +{ >> + struct kvm_vcpu *vcpu; >> + struct kvm_pmu *pmu; >> + >> + pmu = container_of(work, struct kvm_pmu, overflow_work); >> + vcpu = kvm_pmc_to_vcpu(&pmu->pmc[0]); > Can you spell this kvm_pmc_to_vcpu(pmu->pmc); ? Of course, that is much better. > >> + >> + kvm_vcpu_kick(vcpu); > How do we guarantee that the vCPU is still around by the time this runs? > Sorry to ask such a horrible question, but I don't see anything associating > the workqueue with the lifetime of the vCPU. That's a very nice catch, indeed the code doesn't guarantee that the VM is still around when the work is executed. I will add an irq_work_sync() call to kvm_pmu_vcpu_destroy() (which is called by kvm_vcpu_destroy() -> kvm_arch_vcpu_destroy()), and to kvm_pmu_vcpu_reset(), similar to how x86 handles it. Thanks, Alex _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel