On Sat, Dec 09, 2017 at 04:33:28PM +0100, Juan Francisco Cantero Hurtado wrote:
> On Thu, Dec 07, 2017 at 02:27:29PM +0100, Landry Breuil wrote:
> > On Thu, Dec 07, 2017 at 11:52:46AM +0100, Martin Pieuchot wrote:
> > > On 07/12/17(Thu) 08:34, Landry Breuil wrote:
> > > > Hi,
> > > >
> > > > i've been having kvm VMs running 6.2 hardlocking/deadlocking since a
> > > > while, all those running on proxmox 5.1 using linux 4.13.8 & qemu-kvm
> > > > 2.9.1. There were hardlocks upon reboot which were 'solved' by disabling
> > > > x2apic emulation in kvm (args: -cpu=kvm64,-x2apic) or giving the host
> > > > cpu flags to the vm (args: -cpu host) but there still remains deadlocks
> > > > during normal operation.
> > > >
> > > > I'm now running a kernel with MP_LOCKDEBUG, so i'm collecting traces in
> > > > the vain hope that it might help someone interested in locking issues.
> > > > Here's the latest one:
> > >
> > > Let me add that when you had x2apic enabled the kernel 'froze' inside
> > > x2apic_readreg, trace below:
> > >
> > > ddb{0}> tr
> > > x2apic_readreg(10) at x2apic_readreg+0xf
> > > lapic_delay(ffff800022136900) at lapic_delay+0x5c
> > > rtcput(ffff800022136960) at rtcput+0x65
> > > resettodr() at resettodr+0x1d6
> > > perform_resettodr(ffffffff81769b29) at perform_resettodr+0x9
> > > taskq_thread(0) at taskq_thread+0x67
> > > end trace frame: 0x0, count: -6
> > >
> > > What you're seeing with a MP_LOCKDEBUG kernel is just a symptom. A CPU
> > > enters DDB because another one is 'frozen' while holding the
> > > KERNEL_LOCK(). What's interesting is that in both case the frozen CPU
> > > is trying to execute apic related code:
> > > - x2apic_readreg
> > > - lapic_delay
> > >
> > > I believe this issue should be reported to KVM developers as well.
> >
> > *very* interestingly, i had a new lock, running bsd.sp.. So i think that
> > rules out openbsd mp.
> >
> > ddb> tr
> > i82489_readreg(0) at i82489_readreg+0xd
> > lapic_delay(ffffffff81a84090) at lapic_delay+0x5c
> > rtcget(ffffffff81a84090) at rtcget+0x1a
> > resettodr() at resettodr+0x3a
> > perform_resettodr(ffffffff81659e99) at perform_resettodr+0x9
> > taskq_thread(0) at taskq_thread+0x57
> > end trace frame: 0x0, count: -6
>
> Try running with "-machine q35". It changes the emulated machine to
> a modern platform.
Right, i suppose that matches https://wiki.qemu.org/Features/Q35,
interesting. Will definitely try, mailed the kvm mailing list but got no
feedback so far.
Thanks!
Landry
