From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45297) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aRI46-0000fc-PX for qemu-devel@nongnu.org; Thu, 04 Feb 2016 06:27:11 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aRI41-0004B6-OG for qemu-devel@nongnu.org; Thu, 04 Feb 2016 06:27:10 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40455) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aRI41-0004B2-GB for qemu-devel@nongnu.org; Thu, 04 Feb 2016 06:27:05 -0500 References: <56B2754B.7030809@redhat.com> <56B28B1C.7060202@redhat.com> <56B2F6EE.6030205@suse.de> From: Paolo Bonzini Message-ID: <56B33584.6070405@redhat.com> Date: Thu, 4 Feb 2016 12:27:00 +0100 MIME-Version: 1.0 In-Reply-To: <56B2F6EE.6030205@suse.de> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] sda abort with virtio-scsi List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Hannes Reinecke , Jim Minter , qemu-devel On 04/02/2016 07:59, Hannes Reinecke wrote: > On 02/04/2016 12:19 AM, Paolo Bonzini wrote: >> >> >> On 03/02/2016 22:46, Jim Minter wrote: >>> I am hitting the following VM lockup issue running a VM with latest >>> RHEL7 kernel on a host also running latest RHEL7 kernel. FWIW I'm us= ing >>> virtio-scsi because I want to use discard=3Dunmap. I ran the VM as f= ollows: >>> >>> /usr/libexec/qemu-kvm -nodefaults \ >>> -cpu host \ >>> -smp 4 \ >>> -m 8192 \ >>> -drive discard=3Dunmap,file=3Dvm.qcow2,id=3Ddisk1,if=3Dnone,cache=3D= unsafe \ >>> -device virtio-scsi-pci \ >>> -device scsi-disk,drive=3Ddisk1 \ >>> -netdev bridge,id=3Dnet0,br=3Dbr0 \ >>> -device virtio-net-pci,netdev=3Dnet0,mac=3D$(utils/random-mac.py) \ >>> -chardev socket,id=3Dchan0,path=3D/tmp/rhev.sock,server,nowait \ >>> -chardev socket,id=3Dchan1,path=3D/tmp/qemu.sock,server,nowait \ >>> -monitor unix:tmp/vm.sock,server,nowait \ >>> -device virtio-serial-pci \ >>> -device virtserialport,chardev=3Dchan0,name=3Dcom.redhat.rhevm.vdsm= \ >>> -device virtserialport,chardev=3Dchan1,name=3Dorg.qemu.guest_agent.= 0 \ >>> -device cirrus-vga \ >>> -vnc none \ >>> -usbdevice tablet >>> >>> The host was busyish at the time, but not excessively (IMO). Nothing >>> untoward in the host's kernel log; host storage subsystem is fine. I >>> didn't get any qemu logs this time around, but I will when the issue >>> next recurs. The VM's full kernel log is attached; here are the >>> highlights: >> >> Hannes, were you going to send a patch to disable time outs? >> > Rah. Didn't I do it already? > Seems like I didn't; will be doing so shortly. >=20 >>> >>> INFO: rcu_sched detected stalls on CPUs/tasks: { 3} (detected by 2, t= =3D60002 jiffies, g=3D5253, c=3D5252, q=3D0) >>> sending NMI to all CPUs: >>> NMI backtrace for cpu 1 >>> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 3.10.0-327.4.5.el7.x86_64 #= 1 >>> Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 >>> task: ffff88023417d080 ti: ffff8802341a4000 task.ti: ffff8802341a4000 >>> RIP: 0010:[] [] native_safe_halt= +0x6/0x10 >>> RSP: 0018:ffff8802341a7e98 EFLAGS: 00000286 >>> RAX: 00000000ffffffed RBX: ffff8802341a4000 RCX: 0100000000000000 >>> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000046 >>> RBP: ffff8802341a7e98 R08: 0000000000000000 R09: 0000000000000000 >>> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001 >>> R13: ffff8802341a4000 R14: ffff8802341a4000 R15: 0000000000000000 >>> FS: 0000000000000000(0000) GS:ffff88023fc80000(0000) knlGS:000000000= 0000000 >>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>> CR2: 00007f4978587008 CR3: 000000003645e000 CR4: 00000000003407e0 >>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >>> Stack: >>> ffff8802341a7eb8 ffffffff8101dbcf ffff8802341a4000 ffffffff81a68260 >>> ffff8802341a7ec8 ffffffff8101e4d6 ffff8802341a7f20 ffffffff810d62e5 >>> ffff8802341a7fd8 ffff8802341a4000 2581685d70de192c 7ba58fdb3a3bc8d4 >>> Call Trace: >>> [] default_idle+0x1f/0xc0 >>> [] arch_cpu_idle+0x26/0x30 >>> [] cpu_startup_entry+0x245/0x290 >>> [] start_secondary+0x1ba/0x230 >>> Code: 00 00 00 00 00 55 48 89 e5 fa 5d c3 66 0f 1f 84 00 00 00 00 00 = 55 48 89 e5 fb 5d c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb f4 <5d> c3= 0f 1f 84 00 00 00 00 00 55 48 89 e5 f4 5d c3 66 0f 1f 84 >>> NMI backtrace for cpu 0=20 >> >> This is the NMI watchdog firing; the CPU got stuck for 20 seconds. Th= e >> issue was not a busy host, but a busy storage (could it be a network >> partition if the disk was hosted on NFS???) >> >> Firing the NMI watchdog is fixed in more recent QEMU, which has >> asynchronous cancellation, assuming you're running RHEL's QEMU 1.5.3 >> (try /usr/libexec/qemu-kvm --version, or rpm -qf /usr/libexec/qemu-kvm= ). >> > Actually, you still cannot do _real_ async cancellation of I/O; the > linux aio subsystem implements io_cancel(), but the cancellation > just aborts the (internal) waitqueue element, not the I/O itself. Right, but at least the TMF is asynchronous. Synchronous TMFs keep the VCPUs in QEMU for many seconds and cause the watchdog to fire. Paolo