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

Lyude Paul
2018-01-24T19:56:54Z

On Wed, 2018-01-24 at 19:13 +0000, Ghannam, Yazen wrote:
> > -----Original Message-----
> > From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel-
> > owner@vger.kernel.org] On Behalf Of Lyude Paul
> > Sent: Wednesday, January 24, 2018 12:49 PM
> > To: Thomas Gleixner <tglx@linutronix.de>
> > Cc: hpa@zytor.com; keith.busch@intel.com; mingo@kernel.org; linux-
> > kernel@vger.kernel.org
> > Subject: Re: "irq/matrix: Spread interrupts on allocation" breaks nouveau
> > in
> > mainline kernel
> >
> > Hi, please ignore the warning: it happens before and after the regressing
> > commit (I didn't actually mean to include it on the log I gave here,
> > whoops).
> > As for how I determined nouveau is getting assigned the same IRQ vector as
> > another device, I checked using /sys/kernel/debug/irq. Additionally; when
> > nouveau does initialize properly after resume (e.g. after reverting this
> > patch) I see it get assigned a seperate vector from the other devices.
> >
>
> +Boris. This thread seems to have split.
>
> Lyude,
> Does the warning show on mainline or does it only show when bisecting?
>
> Sorry, I'm not sure what you mean by "it happens before and after the
> regressing commit".
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:

Before suspend, nouveau's IRQ allocation:

handler: handle_edge_irq
device: 0000:22:00.0
status: 0x00000000
istate: 0x00000000
ddepth: 0
wdepth: 0
dstate: 0x01400200
IRQD_ACTIVATED
IRQD_IRQ_STARTED
IRQD_SINGLE_TARGET
node: 0
affinity: 0-7
effectiv: 1
pending:
domain: PCI-MSI-2
hwirq: 0x1100000
chip: PCI-MSI
flags: 0x10
IRQCHIP_SKIP_SET_WAKE
parent:
domain: VECTOR
hwirq: 0x2f
chip: APIC
flags: 0x0
Vector: 35
Target: 1

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

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:
handler: handle_edge_irq
device: 0000:22:00.0
status: 0x00000000
istate: 0x00000000
ddepth: 0
wdepth: 0
dstate: 0x01400200
IRQD_ACTIVATED
IRQD_IRQ_STARTED
IRQD_SINGLE_TARGET
node: 0
affinity: 0-7
effectiv: 1
pending:
domain: PCI-MSI-2
hwirq: 0x1100000
chip: PCI-MSI
flags: 0x10
IRQCHIP_SKIP_SET_WAKE
parent:
domain: VECTOR
hwirq: 0x2f
chip: APIC
flags: 0x0
Vector: 35
Target: 1

and the PCI bridge (00:01.3 PCI bridge: Advanced Micro Devices, Inc. [AMD]
Family 17h (Models 00h-0fh) PCIe GPP Bridge):

handler: handle_edge_irq
device: 0000:00:01.3
status: 0x00000000
istate: 0x00000000
ddepth: 0
wdepth: 0
dstate: 0x03400200
IRQD_ACTIVATED
IRQD_IRQ_STARTED
IRQD_SINGLE_TARGET
node: 0
affinity: 0-7
effectiv: 0
pending:
domain: PCI-MSI-2
hwirq: 0x5800
chip: PCI-MSI
flags: 0x10
IRQCHIP_SKIP_SET_WAKE
parent:
domain: VECTOR
hwirq: 0x19
chip: APIC
flags: 0x0
Vector: 35
Target: 0

hope this helps clarify, I will keep looking at this from my end as well
>
>
> Boris,
> In any case, I like your idea on saving the block addresses. I can look into
> this.
>
> Thanks,
> Yazen
--
Cheers,
Lyude Paul