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Re: [Xen-devel] [xen-unstable test] 33690: regressions - FAIL

On 01/26/2015 09:49 AM, Andrew Cooper wrote:
On 26/01/15 11:38, Jan Beulich wrote:
On 26.01.15 at 12:04, <JBeulich@xxxxxxxx> wrote:
On 24.01.15 at 13:54, <Ian.Jackson@xxxxxxxxxxxxx> wrote:
  test-amd64-amd64-xl-qemut-win7-amd64  7 windows-install   fail REGR. vs. 33637
Jan 24 00:35:16.262627 (XEN) ----[ Xen-4.6-unstable  x86_64  debug=y  Not 
tainted ]----
Jan 24 00:35:16.478599 (XEN) CPU:    1
Jan 24 00:35:16.478624 (XEN) RIP:    e008:[<0000000000000000>] 0000000000000000
Jan 24 00:35:16.486596 (XEN) RFLAGS: 0000000000010082   CONTEXT: hypervisor
Jan 24 00:35:16.678620 (XEN) Xen call trace:
Jan 24 00:35:16.678650 (XEN)    [<ffff82d0801d36d0>] vpmu_do_interrupt+0x2f/0x8a
Jan 24 00:35:16.686605 (XEN)    [<ffff82d08015e242>] 
Jan 24 00:35:16.698582 (XEN)    [<ffff82d080171bf0>] do_IRQ+0x9c/0x624
Jan 24 00:35:16.698615 (XEN)    [<ffff82d080234062>] common_interrupt+0x62/0x70
Jan 24 00:35:16.698653 (XEN)    [<ffff82d08012c6fe>] _spin_unlock_irq+0x30/0x31
Jan 24 00:35:16.706604 (XEN)    [<ffff82d08012bcf1>] __do_softirq+0x81/0x8c
Jan 24 00:35:16.706638 (XEN)    [<ffff82d08012bd49>] do_softirq+0x13/0x15
Jan 24 00:35:16.718591 (XEN)    [<ffff82d0801ec4da>] 
I think I see what the problem here is: Commit 8097616fbd
("x86/VPMU: handle APIC_LVTPC accesses") gives the guest
control over LVTPC.mask regardless of whether the vPMU was
actually initialized for it. Supposedly in the case above the
guest is being run with core2_no_vpmu_ops, which in
particular has .do_interrupt == NULL. It's not immediately
clear whether vpmu_lvtpc_update() should do the check or its
(sole) caller. In any event I'm going to revert that commit as
the primary suspect for causing the regression.
I have just fallen over this as well.  I second a revert in the absence
of a clear way to fix the patch.

I can't reproduce this -- neither at this patch level nor at full series.

Yes, we can test for do_interrupt presence in vpmu_lvtpc_update() (or in vpmu_interrupt() itself) but since we cannot arm the counters (there is no do_wrmsr op) I am not sure I understand what can trigger this interrupt.


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