Date:   Wed, 24 Jan 2018 15:02:01 -0500
From:   Lyude Paul <lyude@...hat.com>
To:     "Ghannam, Yazen" <Yazen.Ghannam@....com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     "hpa@...or.com" <hpa@...or.com>,
        "keith.busch@...el.com" <keith.busch@...el.com>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: "irq/matrix: Spread interrupts on allocation" breaks nouveau in
 mainline kernel

On Wed, 2018-01-24 at 14:56 -0500, Lyude Paul wrote:
> On Wed, 2018-01-24 at 19:13 +0000, Ghannam, Yazen wrote:
> > > -----Original Message-----
> > > From: linux-kernel-owner@...r.kernel.org [mailto:linux-kernel-
> > > owner@...r.kernel.org] On Behalf Of Lyude Paul
> > > Sent: Wednesday, January 24, 2018 12:49 PM
> > > To: Thomas Gleixner <tglx@...utronix.de>
> > > Cc: hpa@...or.com; keith.busch@...el.com; mingo@...nel.org; linux-
> > > kernel@...r.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
>     > 
Almost forgot to mention: I came across this patch because reverting it
locally on the mainline kernel makes request_irq() behave normally (it doesn't
attempt to allocate the same vector twice anymore) and nouveau starts doing
suspend/resume correctly again
> > 
> > Boris,
> > In any case, I like your idea on saving the block addresses. I can look
> > into
> > this.
> > 
> > Thanks,
> > Yazen
-- 
Cheers,
	Lyude Paul

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