Re: "irq/matrix: Spread interrupts on allocation" breaks nouveau in mainline kernel

Lyude Paul
2018-01-25T18:24:02Z

I think you are right, apologies. Glad to know this isn't a regression in the
IRQ handling code :). It looks like our nouveau problems are probably coming
from the fact that we don't just leave IRQs setup through suspend/resume which
as far as I can tell, is probably not the correct thing to do.

Going to get some patches onto the mailing list for this, thanks for the help!

On Thu, 2018-01-25 at 09:54 +0100, Thomas Gleixner wrote:
> On Wed, 24 Jan 2018, Lyude Paul wrote:
> > Sorry about that! Let me clarify a little bit: this is a problem that shows
> > up
> > on mainline. Normally when we suspend the GPU in nouveau, we free the IRQs
> > it's using before going into suspend
> > (drivers/gpu/drm/nouveau/nvkm/subdev/pci/base.c:88), then reserve IRQs again
> > on resume (drivers/gpu/drm/nouveau/nvkm/subdev/pci/base.c:134). Since this
> > patch got pushed to mainline, the IRQ we get from request_irq() ends up
> > having
> > the same MSI vector as another device on the system:
>
> It's not the same.
>
> > nouveau:
> > parent:
> > domain: VECTOR
> > hwirq: 0x2f
> > chip: APIC
> > flags: 0x0
> > Vector: 35
> > Target: 1
>
> Vector 35 on CPU1
>
> > After resume and allocating the interrupt for nouveau again, we get a
> > message
> > from the kernel saying:
> >
> > [ 217.150787] do_IRQ: 1.35 No irq handler for vector
>
> That's because there is a pending irq on the old vector for unknown reasons.
>
> > As well, nouveau ends up getting no interrupts from the card and as a
> > result
> > fails to come back up:
> >
> > [ 219.153049] nouveau 0000:22:00.0: DRM: EVO timeout
> > [ 220.226254] r8169 0000:1e:00.0 enp30s0: link up
> > [ 221.153054] nouveau 0000:22:00.0: DRM: base-0: timeout
> > [ 223.153528] nouveau 0000:22:00.0: DRM: base-0: timeout
> >
> > If we look through all of the other IRQ allocations, we'll find that now
> > two
> > devices have the MSI vector 35:
> >
> > nouveau:
> > parent:
> > domain: VECTOR
> > hwirq: 0x2f
> > chip: APIC
> > flags: 0x0
> > Vector: 35
> > Target: 1
>
> Vector 35 on CPU1
>
> > and the PCI bridge (00:01.3 PCI bridge: Advanced Micro Devices, Inc.
> > [AMD]
> > Family 17h (Models 00h-0fh) PCIe GPP Bridge):
> >
> > parent:
> > domain: VECTOR
> > hwirq: 0x19
> > chip: APIC
> > flags: 0x0
> > Vector: 35
> > Target: 0
>
> Vector 35 on CPU0. Same vector but different CPUs. So it's NOT the same
> thing.
>
> The real issue is something completely different and the revert of this
> patch merily papers over the underlying problem. I'm pretty sure that you
> can trigger this even with the revert in place. Do the following before
> suspend:
>
> echo 2 >/proc/irq/$NOUVEAUIRQ/smp_affinity_list
>
> Then do suspend/resume and you should end up with the same situation.
>
> I can't tell from your dmesg, but I'm pretty confident that
>
> > [ 217.150787] do_IRQ: 1.35 No irq handler for vector
>
> happens _before_ the nouveau driver requests the irq again. Can please you
> add some printk to the code in question to verify that?
>
> Thanks,
>
> tglx