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References: <20220429195350.85620-1-lyude@redhat.com> <CACO55tuY6ACoW5jgRk8jCVZ_ZZDEBXczkaiTSpFDvw2h81r=xA@mail.gmail.com>
 <a16299814fbbb4cad99f7c7bc9b83c7c31b63a69.camel@redhat.com>
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From:   Karol Herbst <kherbst@redhat.com>
Date:   Sat, 30 Apr 2022 11:23:26 +0200
Message-ID: <CACO55ttVm0fkUd91E_FHUdvP5HDDk3+qKyJoRYVPGmp-TukNAA@mail.gmail.com>
Subject: Re: [PATCH] drm/nouveau/subdev/bus: Ratelimit logging for fault errors
To:     Lyude Paul <lyude@redhat.com>
Cc:     nouveau <nouveau@lists.freedesktop.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Ben Skeggs <bskeggs@redhat.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        open list <linux-kernel@vger.kernel.org>
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On Sat, Apr 30, 2022 at 1:04 AM Lyude Paul <lyude@redhat.com> wrote:
>
> On Sat, 2022-04-30 at 00:56 +0200, Karol Herbst wrote:
> > On Fri, Apr 29, 2022 at 9:54 PM Lyude Paul <lyude@redhat.com> wrote:
> > >
> > > There's plenty of ways to fudge the GPU when developing on nouveau by
> > > mistake, some of which can result in nouveau seriously spamming dmesg with
> > > fault errors. This can be somewhat annoying, as it can quickly overrun the
> > > message buffer (or your terminal emulator's buffer) and get rid of
> > > actually
> > > useful feedback from the driver. While working on my new atomic only MST
> > > branch, I ran into this issue a couple of times.
> > >
> > > So, let's fix this by adding nvkm_error_ratelimited(), and using it to
> > > ratelimit errors from faults. This should be fine for developers, since
> > > it's nearly always only the first few faults that we care about seeing.
> > > Plus, you can turn off rate limiting in the kernel if you really need to.
> > >
> >
> > good idea :)
> >
> > Although I think we ultimately need a detection of "GPU state is
> > trashed" where we cease to do anything and disable interrupts as some
> > of those issues actually cause the kernel to get DOSed by nouveau
> > spamming/handling interrupts. Not sure if we should go with this patch
> > in the meantime, or if we should just go straight ahead and disable
> > interrupts, which would also stop the spam.
> >
> > Do you know if this patch here is enough to get the system to reboot
> > normally or is it only spamming less?
>
> I'd have to try to come up with a setup that can hit this again, although it
> might not be that hard - last time I hit this it was because I was programming
> the wrong PBN values for MST payloads into nvidia's hardware.
>
> So I can't remember for sure if I could reboot, but I do know I could actually
> log into the system easily and do stuff with ratelimiting applied so it's
> definitely better then the current situation.
>

I can play around with your patch a little, as with broken
multithreading and OpenCL I can trash my entire machine within split
seconds quite reliably :)

> >
> > > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > > ---
> > >  drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h |  2 ++
> > >  drivers/gpu/drm/nouveau/nvkm/subdev/bus/gf100.c    | 14 +++++++-------
> > >  drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv31.c     |  6 +++---
> > >  drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv50.c     |  6 +++---
> > >  4 files changed, 15 insertions(+), 13 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h
> > > b/drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h
> > > index 1665738948fb..96113c8bee8c 100644
> > > --- a/drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h
> > > +++ b/drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h
> > > @@ -62,4 +62,6 @@ void nvkm_subdev_intr(struct nvkm_subdev *);
> > >  #define nvkm_debug(s,f,a...) nvkm_printk((s), DEBUG,   info, f, ##a)
> > >  #define nvkm_trace(s,f,a...) nvkm_printk((s), TRACE,   info, f, ##a)
> > >  #define nvkm_spam(s,f,a...)  nvkm_printk((s),  SPAM,    dbg, f, ##a)
> > > +
> > > +#define nvkm_error_ratelimited(s,f,a...) nvkm_printk((s), ERROR,
> > > err_ratelimited, f, ##a)
> > >  #endif
> > > diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/bus/gf100.c
> > > b/drivers/gpu/drm/nouveau/nvkm/subdev/bus/gf100.c
> > > index 53a6651ac225..80b5aaceeaad 100644
> > > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/bus/gf100.c
> > > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/bus/gf100.c
> > > @@ -35,13 +35,13 @@ gf100_bus_intr(struct nvkm_bus *bus)
> > >                 u32 addr = nvkm_rd32(device, 0x009084);
> > >                 u32 data = nvkm_rd32(device, 0x009088);
> > >
> > > -               nvkm_error(subdev,
> > > -                          "MMIO %s of %08x FAULT at %06x [ %s%s%s]\n",
> > > -                          (addr & 0x00000002) ? "write" : "read", data,
> > > -                          (addr & 0x00fffffc),
> > > -                          (stat & 0x00000002) ? "!ENGINE " : "",
> > > -                          (stat & 0x00000004) ? "PRIVRING " : "",
> > > -                          (stat & 0x00000008) ? "TIMEOUT " : "");
> > > +               nvkm_error_ratelimited(subdev,
> > > +                                      "MMIO %s of %08x FAULT at %06x [
> > > %s%s%s]\n",
> > > +                                      (addr & 0x00000002) ? "write" :
> > > "read", data,
> > > +                                      (addr & 0x00fffffc),
> > > +                                      (stat & 0x00000002) ? "!ENGINE " :
> > > "",
> > > +                                      (stat & 0x00000004) ? "PRIVRING " :
> > > "",
> > > +                                      (stat & 0x00000008) ? "TIMEOUT " :
> > > "");
> > >
> > >                 nvkm_wr32(device, 0x009084, 0x00000000);
> > >                 nvkm_wr32(device, 0x001100, (stat & 0x0000000e));
> > > diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv31.c
> > > b/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv31.c
> > > index ad8da523bb22..c75e463f3501 100644
> > > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv31.c
> > > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv31.c
> > > @@ -45,9 +45,9 @@ nv31_bus_intr(struct nvkm_bus *bus)
> > >                 u32 addr = nvkm_rd32(device, 0x009084);
> > >                 u32 data = nvkm_rd32(device, 0x009088);
> > >
> > > -               nvkm_error(subdev, "MMIO %s of %08x FAULT at %06x\n",
> > > -                          (addr & 0x00000002) ? "write" : "read", data,
> > > -                          (addr & 0x00fffffc));
> > > +               nvkm_error_ratelimited(subdev, "MMIO %s of %08x FAULT at
> > > %06x\n",
> > > +                                      (addr & 0x00000002) ? "write" :
> > > "read", data,
> > > +                                      (addr & 0x00fffffc));
> > >
> > >                 stat &= ~0x00000008;
> > >                 nvkm_wr32(device, 0x001100, 0x00000008);
> > > diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv50.c
> > > b/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv50.c
> > > index 3a1e45adeedc..2055d0b100d3 100644
> > > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv50.c
> > > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv50.c
> > > @@ -60,9 +60,9 @@ nv50_bus_intr(struct nvkm_bus *bus)
> > >                 u32 addr = nvkm_rd32(device, 0x009084);
> > >                 u32 data = nvkm_rd32(device, 0x009088);
> > >
> > > -               nvkm_error(subdev, "MMIO %s of %08x FAULT at %06x\n",
> > > -                          (addr & 0x00000002) ? "write" : "read", data,
> > > -                          (addr & 0x00fffffc));
> > > +               nvkm_error_ratelimited(subdev, "MMIO %s of %08x FAULT at
> > > %06x\n",
> > > +                                      (addr & 0x00000002) ? "write" :
> > > "read", data,
> > > +                                      (addr & 0x00fffffc));
> > >
> > >                 stat &= ~0x00000008;
> > >                 nvkm_wr32(device, 0x001100, 0x00000008);
> > > --
> > > 2.35.1
> > >
> >
>
> --
> Cheers,
>  Lyude Paul (she/her)
>  Software Engineer at Red Hat
>