linux-kernel - Re: Circular lockdep in kvm_reset

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Date:   Tue, 14 Mar 2023 11:04:00 +0000
From:   Cristian Marussi <cristian.marussi@....com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Oliver Upton <oliver.upton@...ux.dev>,
        Jeremy Linton <jeremy.linton@....com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: Circular lockdep in kvm_reset_vcpu() ?

On Tue, Mar 14, 2023 at 09:28:25AM +0000, Marc Zyngier wrote:
> On 2023-03-13 18:20, Cristian Marussi wrote:
> > On Mon, Mar 13, 2023 at 02:09:55PM +0000, Marc Zyngier wrote:
> 
> > > And -rc2 works just fine here.
> > 
> > Thanks, I'll dig deeper what's going on un my setup.
> 
> Actually, you really want this patch[1] which is on its
> way to Linus.
> 
> It could explain the issue you're seeing with SMP.

Hi Marc,

thanks this just solves for me on JUNO with guest SMP.

Indeed with earlycon on JUNO with SMP I was seeing, beside a lot of
workqueue lockup that finally hanged the guest, some puzzling
'time-traveling' stamps that seemed to align more with the host time
than the guest.

    [    0.509305] thermal_sys: Registered thermal governor 'step_wise'
    [    0.509327] thermal_sys: Registered thermal governor 'power_allocator'
    [  282.404523] audit: type=2000 audit(0.372:1): state=initialized audit_enabled=0 res=1
    [    0.526380] cpuidle: using governor menu
    [    0.530378] hw-breakpoint: found 6 breakpoint and 4 watchpoint registers.
    [    0.536241] ASID allocator initialised with 65536 entries
    [    0.547455] Serial: AMBA PL011 UART driver
    [    0.563267] Callback from call_rcu_tasks() invoked.
    [  282.463816] KASLR disabled due to lack of seed
    [  282.470356] HugeTLB: registered 1.00 GiB page size, pre-allocated 0 pages
    [  282.476182] HugeTLB: 0 KiB vmemmap can be freed for a 1.00 GiB page
    ....
    .....
    [  345.799753] io scheduler bfq registered
    [  126.753573] watchdog: BUG: soft lockup - CPU#0 stuck for 118s! [kworker/u4:0:9]
    [  126.759801] Modules linked in:
    [  126.762397] irq event stamp: 713

Thanks a lot for the help.
Cristian