Re: [PATCH] drm/amdgpu: add missing error handling for amdgpu_ring_alloc()

[Christian König <christian.koenig@xxxxxxx>]

Am 21.06.24 um 11:24 schrieb Bob Zhou:
> Fix the unchecked return value warning reported by Coverity,
> so add error handling.

That seems to be completely superfluous. The only case when 
amdgpu_ring_alloc() returns an error is when we try to allocate more 
than the maximum submission size.

And in that case we will get quite a warning already.

I strongly suggest to instead drop the return value from 
amdgpu_ring_alloc().

Regards,
Christian.

> Signed-off-by: Bob Zhou <bob.zhou@xxxxxxx>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c      | 7 +++++--
>   drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c      | 4 +++-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ring_mux.c | 6 ++++--
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vpe.c      | 3 ++-
>   drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c        | 8 ++++++--
>   drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c       | 6 +++++-
>   drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c       | 6 +++++-
>   drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c       | 6 +++++-
>   8 files changed, 35 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
> index 82452606ae6c..25cab6a8d478 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
> @@ -1005,7 +1005,8 @@ uint32_t amdgpu_kiq_rreg(struct amdgpu_device *adev, uint32_t reg, uint32_t xcc_
>   		pr_err("critical bug! too many kiq readers\n");
>   		goto failed_unlock;
>   	}
> -	amdgpu_ring_alloc(ring, 32);
> +	if (amdgpu_ring_alloc(ring, 32))
> +		goto failed_unlock;
>   	amdgpu_ring_emit_rreg(ring, reg, reg_val_offs);
>   	r = amdgpu_fence_emit_polling(ring, &seq, MAX_KIQ_REG_WAIT);
>   	if (r)
> @@ -1071,7 +1072,8 @@ void amdgpu_kiq_wreg(struct amdgpu_device *adev, uint32_t reg, uint32_t v, uint3
>   	}
>   
>   	spin_lock_irqsave(&kiq->ring_lock, flags);
> -	amdgpu_ring_alloc(ring, 32);
> +	if (amdgpu_ring_alloc(ring, 32))
> +		goto failed_unlock;
>   	amdgpu_ring_emit_wreg(ring, reg, v);
>   	r = amdgpu_fence_emit_polling(ring, &seq, MAX_KIQ_REG_WAIT);
>   	if (r)
> @@ -1107,6 +1109,7 @@ void amdgpu_kiq_wreg(struct amdgpu_device *adev, uint32_t reg, uint32_t v, uint3
>   
>   failed_undo:
>   	amdgpu_ring_undo(ring);
> +failed_unlock:
>   	spin_unlock_irqrestore(&kiq->ring_lock, flags);
>   failed_kiq_write:
>   	dev_err(adev->dev, "failed to write reg:%x\n", reg);
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> index 3a7622611916..778941f47c96 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> @@ -768,7 +768,8 @@ void amdgpu_gmc_fw_reg_write_reg_wait(struct amdgpu_device *adev,
>   	}
>   
>   	spin_lock_irqsave(&kiq->ring_lock, flags);
> -	amdgpu_ring_alloc(ring, 32);
> +	if (amdgpu_ring_alloc(ring, 32))
> +		goto failed_unlock;
>   	amdgpu_ring_emit_reg_write_reg_wait(ring, reg0, reg1,
>   					    ref, mask);
>   	r = amdgpu_fence_emit_polling(ring, &seq, MAX_KIQ_REG_WAIT);
> @@ -798,6 +799,7 @@ void amdgpu_gmc_fw_reg_write_reg_wait(struct amdgpu_device *adev,
>   
>   failed_undo:
>   	amdgpu_ring_undo(ring);
> +failed_unlock:
>   	spin_unlock_irqrestore(&kiq->ring_lock, flags);
>   failed_kiq:
>   	dev_err(adev->dev, "failed to write reg %x wait reg %x\n", reg0, reg1);
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring_mux.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring_mux.c
> index d234b7ccfaaf..01864990a192 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring_mux.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring_mux.c
> @@ -63,12 +63,14 @@ static void amdgpu_ring_mux_copy_pkt_from_sw_ring(struct amdgpu_ring_mux *mux,
>   		return;
>   	}
>   	if (start > end) {
> -		amdgpu_ring_alloc(real_ring, (ring->ring_size >> 2) + end - start);
> +		if (amdgpu_ring_alloc(real_ring, (ring->ring_size >> 2) + end - start))
> +			return;
>   		amdgpu_ring_write_multiple(real_ring, (void *)&ring->ring[start],
>   					   (ring->ring_size >> 2) - start);
>   		amdgpu_ring_write_multiple(real_ring, (void *)&ring->ring[0], end);
>   	} else {
> -		amdgpu_ring_alloc(real_ring, end - start);
> +		if (amdgpu_ring_alloc(real_ring, end - start))
> +			return;
>   		amdgpu_ring_write_multiple(real_ring, (void *)&ring->ring[start], end - start);
>   	}
>   }
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vpe.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vpe.c
> index bad232859972..d7d68e61506d 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vpe.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vpe.c
> @@ -610,7 +610,8 @@ static int vpe_ring_preempt_ib(struct amdgpu_ring *ring)
>   
>   	/* emit the trailing fence */
>   	ring->trail_seq += 1;
> -	amdgpu_ring_alloc(ring, 10);
> +	if (amdgpu_ring_alloc(ring, 10))
> +		return -ENOMEM;
>   	vpe_ring_emit_fence(ring, ring->trail_fence_gpu_addr, ring->trail_seq, 0);
>   	amdgpu_ring_commit(ring);
>   
> diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> index 2929c8972ea7..810f7f7e279d 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> @@ -4093,7 +4093,8 @@ static uint64_t gfx_v9_0_kiq_read_clock(struct amdgpu_device *adev)
>   		pr_err("critical bug! too many kiq readers\n");
>   		goto failed_unlock;
>   	}
> -	amdgpu_ring_alloc(ring, 32);
> +	if (amdgpu_ring_alloc(ring, 32))
> +		goto failed_unlock;
>   	amdgpu_ring_write(ring, PACKET3(PACKET3_COPY_DATA, 4));
>   	amdgpu_ring_write(ring, 9 |	/* src: register*/
>   				(5 << 8) |	/* dst: memory */
> @@ -5639,7 +5640,10 @@ static int gfx_v9_0_ring_preempt_ib(struct amdgpu_ring *ring)
>   	amdgpu_ring_set_preempt_cond_exec(ring, false);
>   
>   	ring->trail_seq += 1;
> -	amdgpu_ring_alloc(ring, 13);
> +	if (amdgpu_ring_alloc(ring, 13)) {
> +		spin_unlock_irqrestore(&kiq->ring_lock, flags);
> +		return -ENOMEM;
> +	}
>   	gfx_v9_0_ring_emit_fence(ring, ring->trail_fence_gpu_addr,
>   				 ring->trail_seq, AMDGPU_FENCE_FLAG_EXEC | AMDGPU_FENCE_FLAG_INT);
>   
> diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c b/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c
> index b7d33d78bce0..07ca9264085b 100644
> --- a/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c
> @@ -1490,7 +1490,11 @@ static int sdma_v5_0_ring_preempt_ib(struct amdgpu_ring *ring)
>   
>   	/* emit the trailing fence */
>   	ring->trail_seq += 1;
> -	amdgpu_ring_alloc(ring, 10);
> +	r = amdgpu_ring_alloc(ring, 10);
> +	if (r) {
> +		DRM_ERROR("ring %d failed to be allocated\n", ring->idx);
> +		return r;
> +	}
>   	sdma_v5_0_ring_emit_fence(ring, ring->trail_fence_gpu_addr,
>   				  ring->trail_seq, 0);
>   	amdgpu_ring_commit(ring);
> diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c b/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
> index cc9e961f0078..d51d5bd7de30 100644
> --- a/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
> +++ b/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
> @@ -1345,7 +1345,11 @@ static int sdma_v5_2_ring_preempt_ib(struct amdgpu_ring *ring)
>   
>   	/* emit the trailing fence */
>   	ring->trail_seq += 1;
> -	amdgpu_ring_alloc(ring, 10);
> +	r = amdgpu_ring_alloc(ring, 10);
> +	if (r) {
> +		DRM_ERROR("ring %d failed to be allocated\n", ring->idx);
> +		return r;
> +	}
>   	sdma_v5_2_ring_emit_fence(ring, ring->trail_fence_gpu_addr,
>   				  ring->trail_seq, 0);
>   	amdgpu_ring_commit(ring);
> diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c b/drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c
> index c833b6b8373b..e82426459cc7 100644
> --- a/drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c
> @@ -1371,7 +1371,11 @@ static int sdma_v6_0_ring_preempt_ib(struct amdgpu_ring *ring)
>   
>   	/* emit the trailing fence */
>   	ring->trail_seq += 1;
> -	amdgpu_ring_alloc(ring, 10);
> +	r = amdgpu_ring_alloc(ring, 10);
> +	if (r) {
> +		DRM_ERROR("ring %d failed to be allocated\n", ring->idx);
> +		return r;
> +	}
>   	sdma_v6_0_ring_emit_fence(ring, ring->trail_fence_gpu_addr,
>   				  ring->trail_seq, 0);
>   	amdgpu_ring_commit(ring);