Re: [Nouveau] [PATCH] drm/nouveau/subdev/bus: Ratelimit logging for fault errors

[Lyude Paul <lyude@redhat.com>]

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.

> 
> > 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