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([2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e]) by smtp.googlemail.com with ESMTPSA id ch28sm9615535edb.72.2021.11.29.11.18.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Nov 2021 11:18:53 -0800 (PST) Message-ID: <880a5727-69d1-72a1-b129-b053781625ad@redhat.com> Date: Mon, 29 Nov 2021 20:18:50 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH v2 11/43] KVM: Don't block+unblock when halt-polling is successful Content-Language: en-US To: Sean Christopherson References: <20211009021236.4122790-1-seanjc@google.com> <20211009021236.4122790-12-seanjc@google.com> <4e883728e3e5201a94eb46b56315afca5e95ad9c.camel@redhat.com> <496c2fc6-26b0-9b5d-32f4-2f9e9dd6a064@redhat.com> From: Paolo Bonzini In-Reply-To: Cc: Cornelia Huck , Wanpeng Li , kvm@vger.kernel.org, David Hildenbrand , linux-kernel@vger.kernel.org, Paul Mackerras , Atish Patra , linux-riscv@lists.infradead.org, Claudio Imbrenda , kvmarm@lists.cs.columbia.edu, Janosch Frank , Marc Zyngier , Joerg Roedel , Huacai Chen , Maxim Levitsky , Christian Borntraeger , Aleksandar Markovic , Albert Ou , kvm-ppc@vger.kernel.org, Paul Walmsley , David Matlack , linux-arm-kernel@lists.infradead.org, Jim Mattson , Anup Patel , linux-mips@vger.kernel.org, Palmer Dabbelt , kvm-riscv@lists.infradead.org, Vitaly Kuznetsov 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-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On 11/29/21 19:55, Sean Christopherson wrote: >> Still it does seem to be a race that happens when IS_RUNNING=true but >> vcpu->mode == OUTSIDE_GUEST_MODE. This patch makes the race easier to >> trigger because it moves IS_RUNNING=false later. > > Oh! Any chance the bug only repros with preemption enabled? That would explain > why I don't see problems, I'm pretty sure I've only run AVIC with a PREEMPT=n. Me too. > svm_vcpu_{un}blocking() are called with preemption enabled, and avic_set_running() > passes in vcpu->cpu. If the vCPU is preempted and scheduled in on a different CPU, > avic_vcpu_load() will overwrite the vCPU's entry with the wrong CPU info. That would make a lot of sense. avic_vcpu_load() can handle svm->avic_is_running = false, but avic_set_running still needs its body wrapped by preempt_disable/preempt_enable. Fedora's kernel is CONFIG_PREEMPT_VOLUNTARY, but I know Maxim uses his own build so it would not surprise me if he used CONFIG_PREEMPT=y. Paolo _______________________________________________ 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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 F2CDFC433F5 for ; Mon, 29 Nov 2021 19:24:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=8jBAVLH+Z/qqAhuNO8h9pAB2VbYGKVD+PKBEJZLsc/4=; b=DF6D+MBfYzJhb2 vD+dI8Oh9EULcFtODDnD/TbjWI8RrGLxgDVsV2Vs6mMRs2cqdgf1zLoglDGB2AnHYyz3F+6a6u3qQ aorFNcq+fD6AHqXrbkbRMtQpz1PuHhkTR7E4Si1a6kWsH6Iqa6B7509mw0urAZajeX8ogd2q+0cIR ggucLEUdTqMwVzVSQ1Cms2rB9Zjj9MbiGEPxsV0ep6iRMtaxg391YoFA8sX1Nt5qk3rTvqPMWwUd7 baJ6AQB5Tu5QSexa9z63t1vuUjw+Fut9n3n7REL/8ednr5Xmhy90oXqv6wMiRr7Qnr3BX9rgp8wZ4 HtFmOGGN7Ob6QV6UuskQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mrmG1-0026DG-Pn; Mon, 29 Nov 2021 19:24:09 +0000 Received: from mail-ed1-x52a.google.com ([2a00:1450:4864:20::52a]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mrmAx-0023o3-J5; Mon, 29 Nov 2021 19:18:57 +0000 Received: by mail-ed1-x52a.google.com with SMTP id v1so76326877edx.2; Mon, 29 Nov 2021 11:18:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=b6e11+CJLAryPIw/7DDSWmANxwHaOEFVgPmI0eD1ehw=; b=Yv9EDK6h14i2Dbj+iAIYK0HlvK2JERVyMLo4AC4eEaaM5uGAacc8HtxG8w/Y/N1eKa zoqVyYrJgoymLJ79VszdPFvZOcROHF7XsZML04k5ATYUCAQQQYdmRFM1zliBw5sA+fUR rGCOh7Dkwc25orqYcXeHYn5++zj+NoIkUF+txgA7cbkgTIdSaLJPMhb1GiDwryyn0Wfc MU5Gbh+ysqRcMgmq6XO0rBfKo/INnGwUPA9nBrqjSM7nJ1s+plFGQd3Vr5vlky9IMZdn wkdyjWJAJzkiJ+6yukZdQ5xwMk5wTjTGyWuy1lXhP9nJ6WRZVyGbloAAqLRFAE+sHa2m tnMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:message-id:date:mime-version:user-agent :subject:content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=b6e11+CJLAryPIw/7DDSWmANxwHaOEFVgPmI0eD1ehw=; b=IqCA2EBBxULU66F0wf1UCY8sERUq54OugE9fjzZew1HN2DiI44wDFm3foy/1YAzQbB nmYktdm9x6JLB1n2CIh9pde0b/tEw9tLyExK1lRcT+vvM74EmHVh6DgrJB4V8pnK1kui g6EGfxQxv2SYnc3dUu3GvDVFDorDQ9WSTvQRbsoBG3iDN1vfx7TLJxb0V3ksGpPrqKZ6 iN6GjTcbajlRpIbeg6eMSfJgEIfV1ZV9WqfeQfLjjoCn2QvdDnz0f0wKpQTROhsqxGPU kPjuDlP0bKYhxArZiN0uuMDQ/ZAT21y06fE/bZSYSPrjqhdTvf88r2hiyTJC+eZ6a7HN nQOA== X-Gm-Message-State: AOAM530JfH0Afc8ClB2RrWDSDT8GKI09C1D707zuFoRjiKF22QHgy1mn tcuDpTFrojqGxw3rvwFRbss= X-Google-Smtp-Source: ABdhPJx2YJ0juUfs4Yk6vuSEcojrZsOKQtVYCvzwUVoRUJT0twH/9lzRN0MjKMCkmooXwTOepr8KsQ== X-Received: by 2002:a17:906:c9d2:: with SMTP id hk18mr4315253ejb.523.1638213533689; Mon, 29 Nov 2021 11:18:53 -0800 (PST) Received: from ?IPV6:2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e? ([2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e]) by smtp.googlemail.com with ESMTPSA id ch28sm9615535edb.72.2021.11.29.11.18.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Nov 2021 11:18:53 -0800 (PST) Message-ID: <880a5727-69d1-72a1-b129-b053781625ad@redhat.com> Date: Mon, 29 Nov 2021 20:18:50 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH v2 11/43] KVM: Don't block+unblock when halt-polling is successful Content-Language: en-US To: Sean Christopherson Cc: Maxim Levitsky , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , James Morse , Alexandru Elisei , Suzuki K Poulose , Atish Patra , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , Oliver Upton , Jing Zhang References: <20211009021236.4122790-1-seanjc@google.com> <20211009021236.4122790-12-seanjc@google.com> <4e883728e3e5201a94eb46b56315afca5e95ad9c.camel@redhat.com> <496c2fc6-26b0-9b5d-32f4-2f9e9dd6a064@redhat.com> From: Paolo Bonzini In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211129_111855_714011_EF92A5D0 X-CRM114-Status: GOOD ( 12.62 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On 11/29/21 19:55, Sean Christopherson wrote: >> Still it does seem to be a race that happens when IS_RUNNING=true but >> vcpu->mode == OUTSIDE_GUEST_MODE. This patch makes the race easier to >> trigger because it moves IS_RUNNING=false later. > > Oh! Any chance the bug only repros with preemption enabled? That would explain > why I don't see problems, I'm pretty sure I've only run AVIC with a PREEMPT=n. Me too. > svm_vcpu_{un}blocking() are called with preemption enabled, and avic_set_running() > passes in vcpu->cpu. If the vCPU is preempted and scheduled in on a different CPU, > avic_vcpu_load() will overwrite the vCPU's entry with the wrong CPU info. That would make a lot of sense. avic_vcpu_load() can handle svm->avic_is_running = false, but avic_set_running still needs its body wrapped by preempt_disable/preempt_enable. Fedora's kernel is CONFIG_PREEMPT_VOLUNTARY, but I know Maxim uses his own build so it would not surprise me if he used CONFIG_PREEMPT=y. Paolo _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 726A7C433F5 for ; Mon, 29 Nov 2021 19:25:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=CXIesCWWl8Hh1zVeSXnAhZp1bY3rb0l2ojKWHk7GOxI=; b=sI1KZCo4r+86j1 KS+0Jj8CGqutcqI0Z+YSCavZ9wDgZf/u5Yy4ddArRwHhvxSAb5R3emMzMs4jXJPBPiIdI3efz1srf rxHqWiDPwZBmAsuEL6hbx2jeGNr4/cwlbATNRTw/Twk+r6Z7FNBQ3xJLuSnkSXRZW2dE/jhIKqT/L mRvniRIG4070u8UDrLYdfSlXGpJXl01hu48H3qg1wSPzAEZ326MXJ0CPsChkf0nv40sQQUs+WvDpt vWG7beEpzRcP3KwAxC2wqA2G0/D/4ZC8DhYyFfjLhvgLapJXaTDuZ8YPEkI3k9VnOkDjIiZ9qEWXf qoZHl7xtJ9O37AiryMXQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mrmEy-0025j6-9G; Mon, 29 Nov 2021 19:23:05 +0000 Received: from mail-ed1-x52a.google.com ([2a00:1450:4864:20::52a]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mrmAx-0023o3-J5; Mon, 29 Nov 2021 19:18:57 +0000 Received: by mail-ed1-x52a.google.com with SMTP id v1so76326877edx.2; Mon, 29 Nov 2021 11:18:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=b6e11+CJLAryPIw/7DDSWmANxwHaOEFVgPmI0eD1ehw=; b=Yv9EDK6h14i2Dbj+iAIYK0HlvK2JERVyMLo4AC4eEaaM5uGAacc8HtxG8w/Y/N1eKa zoqVyYrJgoymLJ79VszdPFvZOcROHF7XsZML04k5ATYUCAQQQYdmRFM1zliBw5sA+fUR rGCOh7Dkwc25orqYcXeHYn5++zj+NoIkUF+txgA7cbkgTIdSaLJPMhb1GiDwryyn0Wfc MU5Gbh+ysqRcMgmq6XO0rBfKo/INnGwUPA9nBrqjSM7nJ1s+plFGQd3Vr5vlky9IMZdn wkdyjWJAJzkiJ+6yukZdQ5xwMk5wTjTGyWuy1lXhP9nJ6WRZVyGbloAAqLRFAE+sHa2m tnMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:message-id:date:mime-version:user-agent :subject:content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=b6e11+CJLAryPIw/7DDSWmANxwHaOEFVgPmI0eD1ehw=; b=IqCA2EBBxULU66F0wf1UCY8sERUq54OugE9fjzZew1HN2DiI44wDFm3foy/1YAzQbB nmYktdm9x6JLB1n2CIh9pde0b/tEw9tLyExK1lRcT+vvM74EmHVh6DgrJB4V8pnK1kui g6EGfxQxv2SYnc3dUu3GvDVFDorDQ9WSTvQRbsoBG3iDN1vfx7TLJxb0V3ksGpPrqKZ6 iN6GjTcbajlRpIbeg6eMSfJgEIfV1ZV9WqfeQfLjjoCn2QvdDnz0f0wKpQTROhsqxGPU kPjuDlP0bKYhxArZiN0uuMDQ/ZAT21y06fE/bZSYSPrjqhdTvf88r2hiyTJC+eZ6a7HN nQOA== X-Gm-Message-State: AOAM530JfH0Afc8ClB2RrWDSDT8GKI09C1D707zuFoRjiKF22QHgy1mn tcuDpTFrojqGxw3rvwFRbss= X-Google-Smtp-Source: ABdhPJx2YJ0juUfs4Yk6vuSEcojrZsOKQtVYCvzwUVoRUJT0twH/9lzRN0MjKMCkmooXwTOepr8KsQ== X-Received: by 2002:a17:906:c9d2:: with SMTP id hk18mr4315253ejb.523.1638213533689; Mon, 29 Nov 2021 11:18:53 -0800 (PST) Received: from ?IPV6:2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e? ([2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e]) by smtp.googlemail.com with ESMTPSA id ch28sm9615535edb.72.2021.11.29.11.18.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Nov 2021 11:18:53 -0800 (PST) Message-ID: <880a5727-69d1-72a1-b129-b053781625ad@redhat.com> Date: Mon, 29 Nov 2021 20:18:50 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH v2 11/43] KVM: Don't block+unblock when halt-polling is successful Content-Language: en-US To: Sean Christopherson Cc: Maxim Levitsky , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , James Morse , Alexandru Elisei , Suzuki K Poulose , Atish Patra , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , Oliver Upton , Jing Zhang References: <20211009021236.4122790-1-seanjc@google.com> <20211009021236.4122790-12-seanjc@google.com> <4e883728e3e5201a94eb46b56315afca5e95ad9c.camel@redhat.com> <496c2fc6-26b0-9b5d-32f4-2f9e9dd6a064@redhat.com> From: Paolo Bonzini In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211129_111855_714011_EF92A5D0 X-CRM114-Status: GOOD ( 12.62 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 11/29/21 19:55, Sean Christopherson wrote: >> Still it does seem to be a race that happens when IS_RUNNING=true but >> vcpu->mode == OUTSIDE_GUEST_MODE. This patch makes the race easier to >> trigger because it moves IS_RUNNING=false later. > > Oh! Any chance the bug only repros with preemption enabled? That would explain > why I don't see problems, I'm pretty sure I've only run AVIC with a PREEMPT=n. Me too. > svm_vcpu_{un}blocking() are called with preemption enabled, and avic_set_running() > passes in vcpu->cpu. If the vCPU is preempted and scheduled in on a different CPU, > avic_vcpu_load() will overwrite the vCPU's entry with the wrong CPU info. That would make a lot of sense. avic_vcpu_load() can handle svm->avic_is_running = false, but avic_set_running still needs its body wrapped by preempt_disable/preempt_enable. Fedora's kernel is CONFIG_PREEMPT_VOLUNTARY, but I know Maxim uses his own build so it would not surprise me if he used CONFIG_PREEMPT=y. Paolo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B8D8DC433EF for ; Mon, 29 Nov 2021 22:40:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234511AbhK2Wn5 (ORCPT ); Mon, 29 Nov 2021 17:43:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35142 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234502AbhK2WnS (ORCPT ); Mon, 29 Nov 2021 17:43:18 -0500 Received: from mail-ed1-x534.google.com (mail-ed1-x534.google.com [IPv6:2a00:1450:4864:20::534]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0EFFCC203968; Mon, 29 Nov 2021 11:18:55 -0800 (PST) Received: by mail-ed1-x534.google.com with SMTP id l25so76130772eda.11; Mon, 29 Nov 2021 11:18:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=b6e11+CJLAryPIw/7DDSWmANxwHaOEFVgPmI0eD1ehw=; b=Yv9EDK6h14i2Dbj+iAIYK0HlvK2JERVyMLo4AC4eEaaM5uGAacc8HtxG8w/Y/N1eKa zoqVyYrJgoymLJ79VszdPFvZOcROHF7XsZML04k5ATYUCAQQQYdmRFM1zliBw5sA+fUR rGCOh7Dkwc25orqYcXeHYn5++zj+NoIkUF+txgA7cbkgTIdSaLJPMhb1GiDwryyn0Wfc MU5Gbh+ysqRcMgmq6XO0rBfKo/INnGwUPA9nBrqjSM7nJ1s+plFGQd3Vr5vlky9IMZdn wkdyjWJAJzkiJ+6yukZdQ5xwMk5wTjTGyWuy1lXhP9nJ6WRZVyGbloAAqLRFAE+sHa2m tnMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:message-id:date:mime-version:user-agent :subject:content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=b6e11+CJLAryPIw/7DDSWmANxwHaOEFVgPmI0eD1ehw=; b=SLP5O1d7fkwxL+83NBeKa4ZhuHfdQtripEi5FgV/ql2UwS7HJCKA9BbyMMptW9HGAA k98Iu139eSUf0Gq3C+ffm5HQC63D/r3zLxCvfL5R9VnQw8zBTYKXUGh0pcToYJek2qDn GUcn+BWDEqjHYboiuqLSr92RGt78Iz+/0UKGyToa6sUWaUzvhntT6NjAIKOD8Fp4De0D gyXp7Wxx/f3PUPMH1JFIXXstY4KMRYmE9qrxocj52Q0JOrzsnDqWspXlvPzdTMeDnHxD EH9qVyJITsyn54CyUBoFki1XjuQHkxvNbyfTfmOouFSZyTDqVvcmVayq2F1qyOXJ4kgL qTyA== X-Gm-Message-State: AOAM5338hzw0w5OtfifO4qWh0FzeyQ5HPjltl/I633k8EQb3NTyC+5Ik KOFKWMIR6NPdAsbzMOellLE= X-Google-Smtp-Source: ABdhPJx2YJ0juUfs4Yk6vuSEcojrZsOKQtVYCvzwUVoRUJT0twH/9lzRN0MjKMCkmooXwTOepr8KsQ== X-Received: by 2002:a17:906:c9d2:: with SMTP id hk18mr4315253ejb.523.1638213533689; Mon, 29 Nov 2021 11:18:53 -0800 (PST) Received: from ?IPV6:2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e? ([2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e]) by smtp.googlemail.com with ESMTPSA id ch28sm9615535edb.72.2021.11.29.11.18.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Nov 2021 11:18:53 -0800 (PST) Sender: Paolo Bonzini Message-ID: <880a5727-69d1-72a1-b129-b053781625ad@redhat.com> Date: Mon, 29 Nov 2021 20:18:50 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH v2 11/43] KVM: Don't block+unblock when halt-polling is successful Content-Language: en-US To: Sean Christopherson Cc: Maxim Levitsky , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , James Morse , Alexandru Elisei , Suzuki K Poulose , Atish Patra , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , Oliver Upton , Jing Zhang References: <20211009021236.4122790-1-seanjc@google.com> <20211009021236.4122790-12-seanjc@google.com> <4e883728e3e5201a94eb46b56315afca5e95ad9c.camel@redhat.com> <496c2fc6-26b0-9b5d-32f4-2f9e9dd6a064@redhat.com> From: Paolo Bonzini In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/29/21 19:55, Sean Christopherson wrote: >> Still it does seem to be a race that happens when IS_RUNNING=true but >> vcpu->mode == OUTSIDE_GUEST_MODE. This patch makes the race easier to >> trigger because it moves IS_RUNNING=false later. > > Oh! Any chance the bug only repros with preemption enabled? That would explain > why I don't see problems, I'm pretty sure I've only run AVIC with a PREEMPT=n. Me too. > svm_vcpu_{un}blocking() are called with preemption enabled, and avic_set_running() > passes in vcpu->cpu. If the vCPU is preempted and scheduled in on a different CPU, > avic_vcpu_load() will overwrite the vCPU's entry with the wrong CPU info. That would make a lot of sense. avic_vcpu_load() can handle svm->avic_is_running = false, but avic_set_running still needs its body wrapped by preempt_disable/preempt_enable. Fedora's kernel is CONFIG_PREEMPT_VOLUNTARY, but I know Maxim uses his own build so it would not surprise me if he used CONFIG_PREEMPT=y. Paolo From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Date: Mon, 29 Nov 2021 19:18:50 +0000 Subject: Re: [PATCH v2 11/43] KVM: Don't block+unblock when halt-polling is successful Message-Id: <880a5727-69d1-72a1-b129-b053781625ad@redhat.com> List-Id: References: <20211009021236.4122790-1-seanjc@google.com> <20211009021236.4122790-12-seanjc@google.com> <4e883728e3e5201a94eb46b56315afca5e95ad9c.camel@redhat.com> <496c2fc6-26b0-9b5d-32f4-2f9e9dd6a064@redhat.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: Sean Christopherson Cc: Cornelia Huck , Wanpeng Li , kvm@vger.kernel.org, David Hildenbrand , linux-kernel@vger.kernel.org, Paul Mackerras , Atish Patra , linux-riscv@lists.infradead.org, Claudio Imbrenda , kvmarm@lists.cs.columbia.edu, Janosch Frank , Marc Zyngier , Joerg Roedel , Huacai Chen , Maxim Levitsky , Christian Borntraeger , Aleksandar Markovic , Albert Ou , kvm-ppc@vger.kernel.org, Paul Walmsley , David Matlack , linux-arm-kernel@lists.infradead.org, Jim Mattson , Anup Patel , linux-mips@vger.kernel.org, Palmer Dabbelt , kvm-riscv@lists.infradead.org, Vitaly Kuznetsov On 11/29/21 19:55, Sean Christopherson wrote: >> Still it does seem to be a race that happens when IS_RUNNING=3Dtrue but >> vcpu->mode =3D OUTSIDE_GUEST_MODE. This patch makes the race easier to >> trigger because it moves IS_RUNNING=FAlse later. >=20 > Oh! Any chance the bug only repros with preemption enabled? That would = explain > why I don't see problems, I'm pretty sure I've only run AVIC with a PREEM= PT=3Dn. Me too. > svm_vcpu_{un}blocking() are called with preemption enabled, and avic_set_= running() > passes in vcpu->cpu. If the vCPU is preempted and scheduled in on a diff= erent CPU, > avic_vcpu_load() will overwrite the vCPU's entry with the wrong CPU info. That would make a lot of sense. avic_vcpu_load() can handle=20 svm->avic_is_running =3D false, but avic_set_running still needs its body=20 wrapped by preempt_disable/preempt_enable. Fedora's kernel is CONFIG_PREEMPT_VOLUNTARY, but I know Maxim uses his=20 own build so it would not surprise me if he used CONFIG_PREEMPT=3Dy. Paolo