Re: qemu emulated machine crashes due to disk timeouts

[maya%NetBSD.org@localhost]

On Thu, May 07, 2020 at 08:49:19AM +1000, Paul Ripke wrote:
> On Sat, May 02, 2020 at 12:02:45PM +1000, Paul Ripke wrote:
> > Since I have my qemu disk images on slow spinning rust host disks, when the
> > host disk is busy (esp. daily+security runs), I find my qemu vm's see disk
> > timeouts, and end up crashing. This isn't great behaviour.
> > 
> > Is anyone else seeing this? Any workarounds? I haven't looked, but I assume
> > I'd be able to just bump the timeouts and/or retries.
> > 
> > Host is amd64, netbsd-9 from the last few days.
> > qemu install is amd64, netbsd-current in the last day or two.
> 
> Bumped ATA_DELAY to 30000 (was 10000), and the VM stayed up overnight,
> only logging the one correctable soft error:
> 
> May  7 04:19:29 qemu /netbsd: [ 16290.3345912] autoconfiguration error: piixide0:0:0: lost interrupt
> May  7 04:19:29 qemu /netbsd: [ 16290.3345912]  type: ata tc_bcount: 512 tc_skip: 0
> May  7 04:19:29 qemu /netbsd: [ 16290.3345912] autoconfiguration error: piixide0:0:0: bus-master DMA error: missing interrupt, status=0x21
> May  7 04:19:29 qemu /netbsd: [ 16290.6088515] wd0a: DMA error writing fsbn 1801813 (wd0 bn 1801876; cn 879 tn 52 sn 20), xfer 38, retry 0
> May  7 04:19:29 qemu /netbsd: [ 16292.6053372] wd0: soft error (corrected) xfer 38
> 
> Would making ATA_DELAY configurable via options(4) be worth it?

QEMU emulation isn't a niche setup, we should aim to have it work out of
the box without adjusting sysctls, IMO.