Re: [PATCH] drm/amdgpu: change the fence ring wait timeout

[Christian König <christian.koenig@xxxxxxx>]

Am 19.01.21 um 04:23 schrieb Deng, Emily:
> [AMD Official Use Only - Internal Distribution Only]
>
> > -----Original Message-----
> > From: amd-gfx <amd-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of
> > Christian König
> > Sent: Tuesday, January 19, 2021 12:04 AM
> > To: Deng, Emily <Emily.Deng@xxxxxxx>; Koenig, Christian
> > <Christian.Koenig@xxxxxxx>; Sun, Roy <Roy.Sun@xxxxxxx>; amd-
> > gfx@xxxxxxxxxxxxxxxxxxxxx
> > Subject: Re: [PATCH] drm/amdgpu: change the fence ring wait timeout
> >
> > Am 18.01.21 um 12:56 schrieb Deng, Emily:
> > > [AMD Official Use Only - Internal Distribution Only]
> > >
> > > > -----Original Message-----
> > > > From: Koenig, Christian <Christian.Koenig@xxxxxxx>
> > > > Sent: Monday, January 18, 2021 3:49 PM
> > > > To: Deng, Emily <Emily.Deng@xxxxxxx>; Sun, Roy <Roy.Sun@xxxxxxx>;
> > > > amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> > > > Subject: Re: [PATCH] drm/amdgpu: change the fence ring wait timeout
> > > >
> > > > Mhm, we could change amdgpu_fence_wait_empty() to timeout. But I
> > > > think that waiting forever here is intentional and the right thing to do.
> > > >
> > > > What happens is that we wait for the hardware to make sure that
> > > > nothing is writing to any memory before we unload the driver.
> > > >
> > > > Now the VCN block has crashed and doesn't respond, but we can't
> > > > guarantee that it is not accidentally writing anywhere.
> > > >
> > > > The only alternative we have is to time out and proceed with the
> > > > driver unload, risking corrupting the memory we free during that
> > > > should the hardware continue to do something.
> > > Hi Christian,
> > >       Thanks your suggestion, but still not quite clearly, could you detail the
> > solution to avoid kernel not lockup?
> >
> > Well as I said that the kernel locks up is intentional here.
> So you think the lock up is better than only some memory corruption?

Yes exactly.

> Because we could give more time, such as 60s to wait, I don't think the fence won't be signaled within 60s if the engine is good. So
> when the engine is ok, it won't cause memory corruption with the timeout. When engine is bad, the fence will never be signaled, so even we force completion, it still won't cause memory corruption.

Unfortunately it's not that easy. See for example some engines keep 
updating statistics (how many bytes written, samples encoded etc...) 
even when the engines is stuck in an endless loop.

> As for sriov, when engine
> is bad, we still could do recover, and do driver reload to make the driver works ok again, so we don't want the kernel lockup.

Well that is certainly something you could try, e.g. wait for empty with 
a timeout and if that times out triggers do a GPU reset and wait again.

Alternative would be to see if we could disable system memory access 
from the device all together with the PCIe config regs if we can't get 
it idle again.

Regards,
Christian.

> > Regards,
> > Christian.
> >
> > > > Regards,
> > > > Christian.
> > > >
> > > > Am 18.01.21 um 03:01 schrieb Deng, Emily:
> > > > > [AMD Official Use Only - Internal Distribution Only]
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Koenig, Christian <Christian.Koenig@xxxxxxx>
> > > > > > Sent: Thursday, January 14, 2021 9:50 PM
> > > > > > To: Deng, Emily <Emily.Deng@xxxxxxx>; Sun, Roy
> > <Roy.Sun@xxxxxxx>;
> > > > > > amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> > > > > > Subject: Re: [PATCH] drm/amdgpu: change the fence ring wait timeout
> > > > > >
> > > > > > Am 14.01.21 um 03:00 schrieb Deng, Emily:
> > > > > > > [AMD Official Use Only - Internal Distribution Only]
> > > > > > >
> > > > > > > > -----Original Message-----
> > > > > > > > From: amd-gfx <amd-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf
> > > > > > > > Of Christian König
> > > > > > > > Sent: Wednesday, January 13, 2021 10:03 PM
> > > > > > > > To: Sun, Roy <Roy.Sun@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> > > > > > > > Subject: Re: [PATCH] drm/amdgpu: change the fence ring wait
> > > > > > > > timeout
> > > > > > > >
> > > > > > > > Am 13.01.21 um 07:36 schrieb Roy Sun:
> > > > > > > > > This fix bug where when the engine hang, the fence ring will
> > > > > > > > > wait without quit and cause kernel crash
> > > > > > > > NAK, this blocking is intentional unlimited because otherwise we
> > > > > > > > will cause a memory corruption.
> > > > > > > >
> > > > > > > > What is the actual bug you are trying to fix here?
> > > > > > > When some engine hang during initialization, the IB test will
> > > > > > > fail, and fence will never come back, then never could wait the fence
> > back.
> > > > > > > Why we need to wait here forever? We'd better not use forever wait
> > > > > > > which
> > > > > > will cause kernel crash and lockup. And we have
> > > > > > amdgpu_fence_driver_force_completion will let memory free. We
> > > > > > should remove all those forever wait, and replace them with one
> > > > > > timeout, and do the correct error process if timeout.
> > > > > >
> > > > > > This wait here is to make sure we never overwrite the software
> > > > > > fence ring buffer. Without it we would not signal all fences in
> > > > > > amdgpu_fence_driver_force_completion() and cause either memory
> > leak
> > > > > > or corruption.
> > > > > >
> > > > > > Waiting here forever is the right thing to do even when that means
> > > > > > that the submission thread gets stuck forever, cause that is still
> > > > > > better than memory corruption.
> > > > > >
> > > > > > But this should never happen in practice and is only here for
> > > > > > precaution. So do you really see that in practice?
> > > > > Yes, we hit the issue when vcn ib test fail. Could you give some
> > > > > suggestions
> > > > about how to fix this?
> > > > > [  958.301685] failed to read reg:1a6c0
> > > > >
> > > > > [  959.036645] gmc_v10_0_process_interrupt: 42 callbacks suppressed
> > > > >
> > > > > [  959.036653] amdgpu 0000:00:07.0: [mmhub] page fault (src_id:0
> > > > > ring:0 vmid:0 pasid:0, for process  pid 0 thread  pid 0)
> > > > >
> > > > > [  959.038043] amdgpu 0000:00:07.0:   in page starting at address
> > > > 0x0000000000567000 from client 18
> > > > > [  959.039014] amdgpu 0000:00:07.0: [mmhub] page fault (src_id:0
> > > > > ring:0 vmid:0 pasid:0, for process  pid 0 thread  pid 0)
> > > > >
> > > > > [  959.040202] amdgpu 0000:00:07.0:   in page starting at address
> > > > 0x0000000000567000 from client 18
> > > > > [  959.041174] amdgpu 0000:00:07.0: [mmhub] page fault (src_id:0
> > > > > ring:0 vmid:0 pasid:0, for process  pid 0 thread  pid 0)
> > > > >
> > > > > [  959.042353] amdgpu 0000:00:07.0:   in page starting at address
> > > > 0x0000000000567000 from client 18
> > > > > [  959.043325] amdgpu 0000:00:07.0: [mmhub] page fault (src_id:0
> > > > > ring:0 vmid:0 pasid:0, for process  pid 0 thread  pid 0)
> > > > >
> > > > > [  959.044508] amdgpu 0000:00:07.0:   in page starting at address
> > > > 0x0000000000567000 from client 18
> > > > > [  959.045480] amdgpu 0000:00:07.0: [mmhub] page fault (src_id:0
> > > > > ring:0 vmid:0 pasid:0, for process  pid 0 thread  pid 0)
> > > > >
> > > > > [  959.046659] amdgpu 0000:00:07.0:   in page starting at address
> > > > 0x0000000000567000 from client 18
> > > > > [  959.047631] amdgpu 0000:00:07.0: [mmhub] page fault (src_id:0
> > > > > ring:0 vmid:0 pasid:0, for process  pid 0 thread  pid 0)
> > > > >
> > > > > [  959.048815] amdgpu 0000:00:07.0:   in page starting at address
> > > > 0x0000000000567000 from client 18
> > > > > [  959.049787] amdgpu 0000:00:07.0: [mmhub] page fault (src_id:0
> > > > > ring:0 vmid:0 pasid:0, for process  pid 0 thread  pid 0)
> > > > >
> > > > > [  959.050973] amdgpu 0000:00:07.0:   in page starting at address
> > > > 0x0000000000567000 from client 18
> > > > > [  959.051950] amdgpu 0000:00:07.0: [mmhub] page fault (src_id:0
> > > > > ring:0 vmid:0 pasid:0, for process  pid 0 thread  pid 0)
> > > > >
> > > > > [  959.053123] amdgpu 0000:00:07.0:   in page starting at address
> > > > 0x0000000000567000 from client 18
> > > > > [  967.208705] amdgpu 0000:00:07.0: [drm:amdgpu_ib_ring_tests
> > > > > [amdgpu]]
> > > > *ERROR* IB test failed on vcn_enc0 (-110).
> > > > > [  967.209879] [drm:amdgpu_device_init [amdgpu]] *ERROR* ib ring
> > > > > test
> > > > failed (-110).
> > > > > [ 1209.384668] INFO: task modprobe:23957 blocked for more than 120
> > > > seconds.
> > > > > [ 1209.385605]       Tainted: G           OE     5.4.0-58-generic #64~18.04.1-
> > > > Ubuntu
> > > > > [ 1209.386451] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> > > > disables this message.
> > > > > [ 1209.387342] modprobe        D    0 23957   1221 0x80004006
> > > > >
> > > > > [ 1209.387344] Call Trace:
> > > > >
> > > > > [ 1209.387354]  __schedule+0x293/0x720
> > > > >
> > > > > [ 1209.387356]  schedule+0x33/0xa0
> > > > >
> > > > > [ 1209.387357]  schedule_timeout+0x1d3/0x320
> > > > >
> > > > > [ 1209.387359]  ? schedule+0x33/0xa0
> > > > >
> > > > > [ 1209.387360]  ? schedule_timeout+0x1d3/0x320
> > > > >
> > > > > [ 1209.387363]  dma_fence_default_wait+0x1b2/0x1e0
> > > > >
> > > > > [ 1209.387364]  ? dma_fence_release+0x130/0x130
> > > > >
> > > > > [ 1209.387366]  dma_fence_wait_timeout+0xfd/0x110
> > > > >
> > > > > [ 1209.387773]  amdgpu_fence_wait_empty+0x90/0xc0 [amdgpu]
> > > > >
> > > > > [ 1209.387839]  amdgpu_fence_driver_fini+0xd6/0x110 [amdgpu]
> > > > > > Regards,
> > > > > > Christian.
> > > > > >
> > > > > > > > Regards,
> > > > > > > > Christian.
> > > > > > > >
> > > > > > > > > Signed-off-by: Roy Sun <Roy.Sun@xxxxxxx>
> > > > > > > > > ---
> > > > > > > > >       drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 48
> > > > > > > > ++++++++++++++++++++---
> > > > > > > > >       1 file changed, 43 insertions(+), 5 deletions(-)
> > > > > > > > >
> > > > > > > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> > > > > > > > > b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> > > > > > > > > index 6b0aeee61b8b..738ea65077ea 100644
> > > > > > > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> > > > > > > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> > > > > > > > > @@ -41,6 +41,8 @@
> > > > > > > > >       #include "amdgpu.h"
> > > > > > > > >       #include "amdgpu_trace.h"
> > > > > > > > >
> > > > > > > > > +#define AMDGPU_FENCE_TIMEOUT  msecs_to_jiffies(1000)
> > #define
> > > > > > > > > +AMDGPU_FENCE_GFX_XGMI_TIMEOUT msecs_to_jiffies(2000)
> > > > > > > > >       /*
> > > > > > > > >        * Fences
> > > > > > > > >        * Fences mark an event in the GPUs pipeline and are used
> > > > > > > > > @@
> > > > > > > > > -104,6
> > > > > > > > > +106,38 @@ static void amdgpu_fence_write(struct amdgpu_ring
> > > > > > > > > +*ring,
> > > > > > > > > +u32
> > > > > > > > seq)
> > > > > > > > >       *drv->cpu_addr = cpu_to_le32(seq);
> > > > > > > > >       }
> > > > > > > > >
> > > > > > > > > +/**
> > > > > > > > > + * amdgpu_fence_wait_timeout - get the fence wait timeout
> > > > > > > > > + *
> > > > > > > > > + * @ring: ring the fence is associated with
> > > > > > > > > + *
> > > > > > > > > + * Returns the value of the fence wait timeout.
> > > > > > > > > + */
> > > > > > > > > +long amdgpu_fence_wait_timeout(struct amdgpu_ring *ring) { long
> > > > > > > > > +tmo_gfx, tmo_mm, tmo; struct amdgpu_device *adev = ring->adev;
> > > > > > > > > +tmo_mm = tmo_gfx = AMDGPU_FENCE_TIMEOUT; if
> > > > > > (amdgpu_sriov_vf(adev))
> > > > > > > > > +{ tmo_mm = 8 * AMDGPU_FENCE_TIMEOUT; } if
> > > > > > > > > +(amdgpu_sriov_runtime(adev)) { tmo_gfx = 8 *
> > > > > > AMDGPU_FENCE_TIMEOUT;
> > > > > > > > > +} else if (adev->gmc.xgmi.hive_id) { tmo_gfx =
> > > > > > > > > +AMDGPU_FENCE_GFX_XGMI_TIMEOUT; } if (ring->funcs->type ==
> > > > > > > > > +AMDGPU_RING_TYPE_UVD ||
> > > > > > > > > +ring->funcs->type == AMDGPU_RING_TYPE_VCE || type ==
> > > > > > > > > +ring->funcs->AMDGPU_RING_TYPE_UVD_ENC || type ==
> > > > > > > > > +ring->funcs->AMDGPU_RING_TYPE_VCN_DEC || type ==
> > > > > > > > > +ring->funcs->AMDGPU_RING_TYPE_VCN_ENC || type ==
> > > > > > > > > +ring->funcs->AMDGPU_RING_TYPE_VCN_JPEG)
> > > > > > > > > +tmo = tmo_mm;
> > > > > > > > > +else
> > > > > > > > > +tmo = tmo_gfx;
> > > > > > > > > +return tmo;
> > > > > > > > > +}
> > > > > > > > > +
> > > > > > > > >       /**
> > > > > > > > >        * amdgpu_fence_read - read a fence value
> > > > > > > > >        *
> > > > > > > > > @@ -166,10 +200,12 @@ int amdgpu_fence_emit(struct
> > amdgpu_ring
> > > > > > > > > *ring,
> > > > > > > > struct dma_fence **f,
> > > > > > > > >       rcu_read_unlock();
> > > > > > > > >
> > > > > > > > >       if (old) {
> > > > > > > > > -r = dma_fence_wait(old, false);
> > > > > > > > > +long timeout;
> > > > > > > > > +timeout = amdgpu_fence_wait_timeout(ring); r =
> > > > > > > > > +dma_fence_wait_timeout(old, false, timeout);
> > > > > > > > >       dma_fence_put(old);
> > > > > > > > >       if (r)
> > > > > > > > > -return r;
> > > > > > > > > +return r < 0 ? r : 0;
> > > > > > > > >       }
> > > > > > > > >       }
> > > > > > > > >
> > > > > > > > > @@ -343,10 +379,12 @@ int amdgpu_fence_wait_empty(struct
> > > > > > > > amdgpu_ring *ring)
> > > > > > > > >       return 0;
> > > > > > > > >       }
> > > > > > > > >       rcu_read_unlock();
> > > > > > > > > -
> > > > > > > > > -r = dma_fence_wait(fence, false);
> > > > > > > > > +
> > > > > > > > > +long timeout;
> > > > > > > > > +timeout = amdgpu_fence_wait_timeout(ring); r =
> > > > > > > > > +dma_fence_wait_timeout(fence, false, timeout);
> > > > > > > > >       dma_fence_put(fence);
> > > > > > > > > -return r;
> > > > > > > > > +return r < 0 ? r : 0;
> > > > > > > > >       }
> > > > > > > > >
> > > > > > > > >       /**
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