On Tue, 10 Jul 2018 08:53:00 -0400 Chris <coderight+l...@gmail.com> wrote:
> I'm getting a 15 second delay on every VM boot when using the > ArchLinux kernel and using the virtio-scsi-pci system. > > QEMU emulator version 2.12.0 running on Arch Linux (4.17.4 kernel), > booting the same. > > I run qemu like so: > > qemu-system-x86_64 \ > -nodefaults \ > -machine type=pc,accel=kvm -smp cores=2,threads=1 -cpu host -vga > vmware -m 2G \ > -device virtio-scsi-pci,id=scsi0,num_queues=2 \ > -drive > id=hdroot,file=archlinux.qcow2,if=none,media=disk,cache=unsafe,format=qcow2 > \ > -device scsi-hd,drive=hdroot > > See the 15 second hang here: > > [ 0.577018] scsi host2: Virtio SCSI HBA > [ 0.578413] scsi 2:0:0:0: Direct-Access QEMU QEMU HARDDISK > 2.5+ PQ: 0 ANSI: 5 > [ 1.333550] tsc: Refined TSC clocksource calibration: 2800.036 MHz > [ 1.335351] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: > 0x285c62b0192, max_idle_ns: 440795270636 ns > [ 17.134876] sd 2:0:0:0: Power-on or device reset occurred > [ 17.137683] sd 2:0:0:0: [sda] 104857600 512-byte logical blocks: > (53.7 GB/50.0 GiB) > [ 17.139845] sd 2:0:0:0: [sda] Write Protect is off > [ 17.140791] sd 2:0:0:0: [sda] Mode Sense: 63 00 00 08 > [ 17.140921] sd 2:0:0:0: [sda] Write cache: enabled, read cache: > enabled, doesn't support DPO or FUA > [ 17.143968] sda: sda1 sda2 > > This is specific to the Arch Linux kernel and the virtio-scsi system. > IDE boots fast. If I boot an Ubuntu kernel with the exact same > virtio-scsi settings then there is no delay for the "Power-on or > device reset occurred" and it boots instantly. > > Anyone know what is going on or what I can do to debug this? > > Thanks > I've been observing a similar delay on ppc64 with fedora28 guests: # dmesg | egrep 'scsi| sd ' [ 1.530946] scsi host0: Virtio SCSI HBA [ 1.532452] scsi 0:0:0:0: Direct-Access QEMU QEMU HARDDISK 2.5+ PQ: 0 ANSI: 5 [ 21.928378] sd 0:0:0:0: Power-on or device reset occurred [ 21.930012] sd 0:0:0:0: Attached scsi generic sg0 type 0 [ 21.931554] sd 0:0:0:0: [sda] 83886080 512-byte logical blocks: (42.9 GB/40.0 GiB) [ 21.931929] sd 0:0:0:0: [sda] Write Protect is off [ 21.933110] sd 0:0:0:0: [sda] Mode Sense: 63 00 00 08 [ 21.934084] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA [ 21.943566] sd 0:0:0:0: [sda] Attached SCSI disk Kernel version is 4.16.16-300.fc28.ppc64. And I cannot reproduce the issue with other distros that have an older kernel, eg, ubuntu 18.04 with kernel 4.15.0-23-generic. My first guess is that it might be a kernel-side regression introduced in 4.16... maybe bisect ? Cheers, -- Greg