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Message-ID: <a5a56eb095d124290b21cfb48fa1a9d002ba0c18.camel@pengutronix.de>
Date: Wed, 12 Jul 2023 12:56:08 +0200
From: Lucas Stach <l.stach@...gutronix.de>
To: Christian König <christian.koenig@....com>,
André Almeida <andrealmeid@...lia.com>,
dri-devel@...ts.freedesktop.org, amd-gfx@...ts.freedesktop.org,
linux-kernel@...r.kernel.org
Cc: pierre-eric.pelloux-prayer@....com,
'Marek Olšák' <maraeo@...il.com>,
Timur Kristóf <timur.kristof@...il.com>,
michel.daenzer@...lbox.org,
Samuel Pitoiset <samuel.pitoiset@...il.com>,
kernel-dev@...lia.com, alexander.deucher@....com
Subject: Re: [PATCH 3/6] drm/amdgpu: Rework coredump to use memory
dynamically
Sorry, accidentally hit sent on the previous mail.
Am Mittwoch, dem 12.07.2023 um 12:39 +0200 schrieb Christian König:
> Am 12.07.23 um 10:59 schrieb Lucas Stach:
> > Am Mittwoch, dem 12.07.2023 um 10:37 +0200 schrieb Christian König:
> > > Am 11.07.23 um 23:34 schrieb André Almeida:
> > > > Instead of storing coredump information inside amdgpu_device struct,
> > > > move if to a proper separated struct and allocate it dynamically. This
> > > > will make it easier to further expand the logged information.
> > > Verry big NAK to this. The problem is that memory allocation isn't
> > > allowed during a GPU reset.
> > >
> > > What you could do is to allocate the memory with GFP_ATOMIC or similar,
> > > but for a large structure that might not be possible.
> > >
> > I'm still not fully clear on what the rules are here. In etnaviv we do
> > devcoredump allocation in the GPU reset path with __GFP_NOWARN |
> > __GFP_NORETRY, which means the allocation will kick memory reclaim if
> > necessary, but will just give up if no memory could be made available
> > easily. This satisfies the forward progress guarantee in the absence of
> > successful memory allocation, which is the most important property in
> > this path, I think.
> >
> > However, I'm not sure if the reclaim could lead to locking issues or
> > something like that with the more complex use-cases with MMU notifiers
> > and stuff like that. Christian, do you have any experience or
> > information that would be good to share in this regard?
>
> Yeah, very good question.
>
> __GFP_NORETRY isn't sufficient as far as I know. Reclaim must be
> completely suppressed to be able to allocate in a GPU reset handler.
>
> Daniel added lockdep annotation to some of the dma-fence signaling paths
> and this yielded quite a bunch of potential deadlocks.
>
> It's not even that reclaim itself waits for dma_fences (that can happen,
> but is quite unlikely), but rather that reclaim needs locks and under
> those locks we then wait for dma_fences.
>
> We should probably add a define somewhere which documents that
> (GFP_ATOMIC | __NO_WARN) should be used in the GPU reset handlers when
> allocating memory for coredumps.
>
Hm, if the problem is the direct reclaim path where we might recurse on
a lock through those indirect dependencies then we should document this
somewhere. kswapd reclaim should be fine as far as I can see, as we'll
guarantee progress without waiting for the background reclaim.
I don't think it's appropriate to dip into the atomic allocation
reserves for a best-effort thing like writing the devcoredump, so I
think this should be GFP_NOWAIT, which will also avoid the direct
reclaim path.
Regards,
Lucas
> Regards,
> Christian.
>
> >
> > Regards,
> > Lucas
> >
> > > Regards,
> > > Christian.
> > >
> > > > Signed-off-by: André Almeida <andrealmeid@...lia.com>
> > > > ---
> > > > drivers/gpu/drm/amd/amdgpu/amdgpu.h | 14 +++--
> > > > drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 65 ++++++++++++++--------
> > > > 2 files changed, 51 insertions(+), 28 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> > > > index dbe062a087c5..e1cc83a89d46 100644
> > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> > > > @@ -1068,11 +1068,6 @@ struct amdgpu_device {
> > > > uint32_t *reset_dump_reg_list;
> > > > uint32_t *reset_dump_reg_value;
> > > > int num_regs;
> > > > -#ifdef CONFIG_DEV_COREDUMP
> > > > - struct amdgpu_task_info reset_task_info;
> > > > - bool reset_vram_lost;
> > > > - struct timespec64 reset_time;
> > > > -#endif
> > > >
> > > > bool scpm_enabled;
> > > > uint32_t scpm_status;
> > > > @@ -1085,6 +1080,15 @@ struct amdgpu_device {
> > > > uint32_t aid_mask;
> > > > };
> > > >
> > > > +#ifdef CONFIG_DEV_COREDUMP
> > > > +struct amdgpu_coredump_info {
> > > > + struct amdgpu_device *adev;
> > > > + struct amdgpu_task_info reset_task_info;
> > > > + struct timespec64 reset_time;
> > > > + bool reset_vram_lost;
> > > > +};
> > > > +#endif
> > > > +
> > > > static inline struct amdgpu_device *drm_to_adev(struct drm_device *ddev)
> > > > {
> > > > return container_of(ddev, struct amdgpu_device, ddev);
> > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > index e25f085ee886..23b9784e9787 100644
> > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > @@ -4963,12 +4963,17 @@ static int amdgpu_reset_reg_dumps(struct amdgpu_device *adev)
> > > > return 0;
> > > > }
> > > >
> > > > -#ifdef CONFIG_DEV_COREDUMP
> > > > +#ifndef CONFIG_DEV_COREDUMP
> > > > +static void amdgpu_coredump(struct amdgpu_device *adev, bool vram_lost,
> > > > + struct amdgpu_reset_context *reset_context)
> > > > +{
> > > > +}
> > > > +#else
> > > > static ssize_t amdgpu_devcoredump_read(char *buffer, loff_t offset,
> > > > size_t count, void *data, size_t datalen)
> > > > {
> > > > struct drm_printer p;
> > > > - struct amdgpu_device *adev = data;
> > > > + struct amdgpu_coredump_info *coredump = data;
> > > > struct drm_print_iterator iter;
> > > > int i;
> > > >
> > > > @@ -4982,21 +4987,21 @@ static ssize_t amdgpu_devcoredump_read(char *buffer, loff_t offset,
> > > > drm_printf(&p, "**** AMDGPU Device Coredump ****\n");
> > > > drm_printf(&p, "kernel: " UTS_RELEASE "\n");
> > > > drm_printf(&p, "module: " KBUILD_MODNAME "\n");
> > > > - drm_printf(&p, "time: %lld.%09ld\n", adev->reset_time.tv_sec, adev->reset_time.tv_nsec);
> > > > - if (adev->reset_task_info.pid)
> > > > + drm_printf(&p, "time: %lld.%09ld\n", coredump->reset_time.tv_sec, coredump->reset_time.tv_nsec);
> > > > + if (coredump->reset_task_info.pid)
> > > > drm_printf(&p, "process_name: %s PID: %d\n",
> > > > - adev->reset_task_info.process_name,
> > > > - adev->reset_task_info.pid);
> > > > + coredump->reset_task_info.process_name,
> > > > + coredump->reset_task_info.pid);
> > > >
> > > > - if (adev->reset_vram_lost)
> > > > + if (coredump->reset_vram_lost)
> > > > drm_printf(&p, "VRAM is lost due to GPU reset!\n");
> > > > - if (adev->num_regs) {
> > > > + if (coredump->adev->num_regs) {
> > > > drm_printf(&p, "AMDGPU register dumps:\nOffset: Value:\n");
> > > >
> > > > - for (i = 0; i < adev->num_regs; i++)
> > > > + for (i = 0; i < coredump->adev->num_regs; i++)
> > > > drm_printf(&p, "0x%08x: 0x%08x\n",
> > > > - adev->reset_dump_reg_list[i],
> > > > - adev->reset_dump_reg_value[i]);
> > > > + coredump->adev->reset_dump_reg_list[i],
> > > > + coredump->adev->reset_dump_reg_value[i]);
> > > > }
> > > >
> > > > return count - iter.remain;
> > > > @@ -5004,14 +5009,34 @@ static ssize_t amdgpu_devcoredump_read(char *buffer, loff_t offset,
> > > >
> > > > static void amdgpu_devcoredump_free(void *data)
> > > > {
> > > > + kfree(data);
> > > > }
> > > >
> > > > -static void amdgpu_reset_capture_coredumpm(struct amdgpu_device *adev)
> > > > +static void amdgpu_coredump(struct amdgpu_device *adev, bool vram_lost,
> > > > + struct amdgpu_reset_context *reset_context)
> > > > {
> > > > + struct amdgpu_coredump_info *coredump;
> > > > struct drm_device *dev = adev_to_drm(adev);
> > > >
> > > > - ktime_get_ts64(&adev->reset_time);
> > > > - dev_coredumpm(dev->dev, THIS_MODULE, adev, 0, GFP_KERNEL,
> > > > + coredump = kmalloc(sizeof(*coredump), GFP_KERNEL);
> > > > +
> > > > + if (!coredump) {
> > > > + DRM_ERROR("%s: failed to allocate memory for coredump\n", __func__);
> > > > + return;
> > > > + }
> > > > +
> > > > + memset(coredump, 0, sizeof(*coredump));
> > > > +
> > > > + coredump->reset_vram_lost = vram_lost;
> > > > +
> > > > + if (reset_context->job && reset_context->job->vm)
> > > > + coredump->reset_task_info = reset_context->job->vm->task_info;
> > > > +
> > > > + coredump->adev = adev;
> > > > +
> > > > + ktime_get_ts64(&coredump->reset_time);
> > > > +
> > > > + dev_coredumpm(dev->dev, THIS_MODULE, coredump, 0, GFP_KERNEL,
> > > > amdgpu_devcoredump_read, amdgpu_devcoredump_free);
> > > > }
> > > > #endif
> > > > @@ -5119,15 +5144,9 @@ int amdgpu_do_asic_reset(struct list_head *device_list_handle,
> > > > goto out;
> > > >
> > > > vram_lost = amdgpu_device_check_vram_lost(tmp_adev);
> > > > -#ifdef CONFIG_DEV_COREDUMP
> > > > - tmp_adev->reset_vram_lost = vram_lost;
> > > > - memset(&tmp_adev->reset_task_info, 0,
> > > > - sizeof(tmp_adev->reset_task_info));
> > > > - if (reset_context->job && reset_context->job->vm)
> > > > - tmp_adev->reset_task_info =
> > > > - reset_context->job->vm->task_info;
> > > > - amdgpu_reset_capture_coredumpm(tmp_adev);
> > > > -#endif
> > > > +
> > > > + amdgpu_coredump(tmp_adev, vram_lost, reset_context);
> > > > +
> > > > if (vram_lost) {
> > > > DRM_INFO("VRAM is lost due to GPU reset!\n");
> > > > amdgpu_inc_vram_lost(tmp_adev);
>
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