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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id on5sm526932pjb.23.2021.12.07.14.25.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Dec 2021 14:25:55 -0800 (PST) Date: Tue, 7 Dec 2021 22:25:51 +0000 From: Sean Christopherson To: Chris Murphy Cc: kvm@vger.kernel.org, qemu-devel@nongnu.org Subject: Re: dozens of qemu/kvm VMs getting into stuck states since kernel ~5.13 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Host-Lookup-Failed: Reverse DNS lookup failed for 2607:f8b0:4864:20::532 (failed) Received-SPF: pass client-ip=2607:f8b0:4864:20::532; envelope-from=seanjc@google.com; helo=mail-pg1-x532.google.com X-Spam_score_int: -167 X-Spam_score: -16.8 X-Spam_bar: ---------------- X-Spam_report: (-16.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_MED=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, ENV_AND_HDR_SPF_MATCH=-0.5, PDS_HP_HELO_NORDNS=0.001, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, USER_IN_DEF_DKIM_WL=-7.5, USER_IN_DEF_SPF_WL=-7.5 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Dec 07, 2021, Chris Murphy wrote: > cc: qemu-devel > > Hi, > > I'm trying to help progress a very troublesome and so far elusive bug > we're seeing in Fedora infrastructure. When running dozens of qemu-kvm > VMs simultaneously, eventually they become unresponsive, as well as > new processes as we try to extract information from the host about > what's gone wrong. Have you tried bisecting? IIUC, the issues showed up between v5.11 and v5.12.12, bisecting should be relatively straightforward. > Systems (Fedora openQA worker hosts) on kernel 5.12.12+ wind up in a > state where forking does not work correctly, breaking most things > https://bugzilla.redhat.com/show_bug.cgi?id=2009585 > > In subsequent testing, we used newer kernels with lockdep and other > debug stuff enabled, and managed to capture a hung task with a bunch > of locks listed, including kvm and qemu processes. But I can't parse > it. > > 5.15-rc7 > https://bugzilla-attachments.redhat.com/attachment.cgi?id=1840941 > 5.15+ > https://bugzilla-attachments.redhat.com/attachment.cgi?id=1840939 > > If anyone can take a glance at those kernel messages, and/or give > hints how we can extract more information for debugging, it'd be > appreciated. Maybe all of that is normal and the actual problem isn't > in any of these traces. All the instances of (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x77/0x720 [kvm] are uninteresting and expected, that's just each vCPU task taking its associated vcpu->mutex, likely for KVM_RUN. At a glance, the XFS stuff looks far more interesting/suspect.