Re: [Xen-devel] Stopping much Linux testing in Xen Project CI

[Jürgen Groß <jgross@xxxxxxxx>]

On 13.03.20 10:13, Jan Beulich wrote:
> On 12.03.2020 18:55, Roger Pau Monné wrote:
> > On Thu, Mar 12, 2020 at 04:49:51PM +0000, Ian Jackson wrote:
> > > Linux stable branches, and Linux upstream tip, are badly broken and
> > > have been for months.  Apparently no-one is able to (or has time to)
> > > to investigate and fix.
> > >
> > >    linux-4.4          218 days         to be suspended
> > >    linux-4.9          134 days         to be suspended
> > >    linux-4.14         134 days         to be suspended
> > >    linux-4.19         134 days         to be suspended
> > >    linux-5.4           55 days
> > >    linux-arm-xen     up to date
> > >    linux-linus        372 days         to be suspended
> > >
> > > These are times since the last push - ie, how long it has been broken.
> > > Evidently no-one is paying any attention to this.[1]  I looked at the
> > > reports myself and:
> > >
> > > Nested HVM is broken on Intel in all of the 4.x branches.
> > FWIW, it's the Debian installer kernel the one that crashes AFAICT,
> > all the failures are:
> >
> > [    0.000000] Linux version 4.9.0-6-amd64 (debian-kernel@xxxxxxxxxxxxxxxx) 
> > (gcc version 6.3.0 20170516 (Debian 6.3.0-18+deb9u1) ) #1 SMP Debian 
> > 4.9.82-1+deb9u3 (2018-03-02)
> > [...]
> > [    0.000000] clocksource: hpet: mask: 0xffffffff max_cycles: 0xffffffff, 
> > max_idle_ns: 30580167144 ns
> > [    0.000000] tsc: Fast TSC calibration failed
> > [    0.000000] tsc: Unable to calibrate against PIT
> > [    0.000000] tsc: HPET/PMTIMER calibration failed
> > [    0.000000] divide error: 0000 [#1] SMP
> > [    0.000000] Modules linked in:
> > [    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.0-6-amd64 #1 
> > Debian 4.9.82-1+deb9u3
> > [    0.000000] Hardware name: Xen HVM domU, BIOS 4.14-unstable 03/11/2020
> > [    0.000000] task: ffffffffab611500 task.stack: ffffffffab600000
> > [    0.000000] RIP: 0010:[<ffffffffaaa59e1f>]  [<ffffffffaaa59e1f>] 
> > pvclock_tsc_khz+0xf/0x30
> Seeing this and ...
>
> > [    0.000000] RSP: 0000:ffffffffab603f38  EFLAGS: 00010246
> > [    0.000000] RAX: 000f424000000000 RBX: ffffffffffffffff RCX: 0000000000000000
> > [    0.000000] RDX: 0000000000000000 RSI: 0000000000000246 RDI: ffffffffab939020
> > [    0.000000] RBP: ffff93806e8f1540 R08: 000000003a637374 R09: 6f6974617262696c
> > [    0.000000] R10: 00000032f3af6dcd R11: 4d502f5445504820 R12: ffffffffab7dc920
> > [    0.000000] R13: ffffffffab7e82e0 R14: 00000000000146f0 R15: 000000000000008e
> > [    0.000000] FS:  0000000000000000(0000) GS:ffff93806e600000(0000) 
> > knlGS:0000000000000000
> > [    0.000000] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [    0.000000] CR2: ffff938065f3a000 CR3: 0000000025c08000 CR4: 00000000000406b0
> > [    0.000000] Stack:
> > [    0.000000]  ffffffffab74b1b6 ffff93806e8f1540 ffffffffab7dc920 
> > ba81e537ba81e512
> > [    0.000000]  ffffffffffffffff ffff93806e8f1540 ffffffffab73deb6 
> > ffffffffab7e82e0
> > [    0.000000]  0000000000000000 0000000000000020 0000ffffffffab73 
> > 00000000ffffffff
> > [    0.000000] Call Trace:
> > [    0.000000]  [<ffffffffab74b1b6>] ? tsc_init+0x39/0x25b
> ... this and looking at xen_tsc_khz(), isn't it supposed to use
> per_cpu(xen_vcpu, 0) instead, in case vCPU info got relocated?
> (Code looks to be the same in 4.9 and 5.5. I'd also question
> the hard-coded zero in there, but that's a different topic.)
It should use per_cpu(xen_vcpu, 0), but OTOH it shouldn't matter that
much if it doesn't, as the time information from the shared info page
wouldn't go away.

Seeing a zero divisor here indicates that HYPERVISOR_shared_info might
still point to the dummy shared info structure.


Juergen

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