Re: [PATCH] drm/amdgpu: fix return random value when multiple threads read registers via mes.

["Christian König" <christian.koenig@amd.com>]

Am 05.11.24 um 03:48 schrieb Chong Li:
> The currect code use the address "adev->mes.read_val_ptr" to
> store the value read from register via mes.
> So when multiple threads read register,
> multiple threads have to share the one address,
> and overwrite the value each other.
>
> Assign an address by "amdgpu_device_wb_get" to store register value.
> each thread will has an address to store register value.
>
> Signed-off-by: Chong Li <chongli2@amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c | 30 +++++++++++--------------
>   drivers/gpu/drm/amd/amdgpu/amdgpu_mes.h |  3 ---
>   2 files changed, 13 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c
> index 83d0f731fb65..d74e3507e155 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c
> @@ -189,17 +189,6 @@ int amdgpu_mes_init(struct amdgpu_device *adev)
>   			(uint64_t *)&adev->wb.wb[adev->mes.query_status_fence_offs[i]];
>   	}
>   
> -	r = amdgpu_device_wb_get(adev, &adev->mes.read_val_offs);
> -	if (r) {
> -		dev_err(adev->dev,
> -			"(%d) read_val_offs alloc failed\n", r);
> -		goto error;
> -	}
> -	adev->mes.read_val_gpu_addr =
> -		adev->wb.gpu_addr + (adev->mes.read_val_offs * 4);
> -	adev->mes.read_val_ptr =
> -		(uint32_t *)&adev->wb.wb[adev->mes.read_val_offs];
> -
>   	r = amdgpu_mes_doorbell_init(adev);
>   	if (r)
>   		goto error;
> @@ -220,8 +209,6 @@ int amdgpu_mes_init(struct amdgpu_device *adev)
>   			amdgpu_device_wb_free(adev,
>   				      adev->mes.query_status_fence_offs[i]);
>   	}
> -	if (adev->mes.read_val_ptr)
> -		amdgpu_device_wb_free(adev, adev->mes.read_val_offs);
>   
>   	idr_destroy(&adev->mes.pasid_idr);
>   	idr_destroy(&adev->mes.gang_id_idr);
> @@ -246,8 +233,6 @@ void amdgpu_mes_fini(struct amdgpu_device *adev)
>   			amdgpu_device_wb_free(adev,
>   				      adev->mes.query_status_fence_offs[i]);
>   	}
> -	if (adev->mes.read_val_ptr)
> -		amdgpu_device_wb_free(adev, adev->mes.read_val_offs);
>   
>   	amdgpu_mes_doorbell_free(adev);
>   
> @@ -918,10 +903,19 @@ uint32_t amdgpu_mes_rreg(struct amdgpu_device *adev, uint32_t reg)
>   {
>   	struct mes_misc_op_input op_input;
>   	int r, val = 0;
> +	uint32_t addr_offset = 0;
> +	uint64_t read_val_gpu_addr = 0;
> +	uint32_t *read_val_ptr = NULL;

Those are unnecessary initialization of local variable. Some automated 
tools will complain about that.

Apart from that looks good to me,
Christian.

>   
> +	if (amdgpu_device_wb_get(adev, &addr_offset)) {
> +		DRM_ERROR("critical bug! too many mes readers\n");
> +		goto error;
> +	}
> +	read_val_gpu_addr = adev->wb.gpu_addr + (addr_offset * 4);
> +	read_val_ptr = (uint32_t *)&adev->wb.wb[addr_offset];
>   	op_input.op = MES_MISC_OP_READ_REG;
>   	op_input.read_reg.reg_offset = reg;
> -	op_input.read_reg.buffer_addr = adev->mes.read_val_gpu_addr;
> +	op_input.read_reg.buffer_addr = read_val_gpu_addr;
>   
>   	if (!adev->mes.funcs->misc_op) {
>   		DRM_ERROR("mes rreg is not supported!\n");
> @@ -932,9 +926,11 @@ uint32_t amdgpu_mes_rreg(struct amdgpu_device *adev, uint32_t reg)
>   	if (r)
>   		DRM_ERROR("failed to read reg (0x%x)\n", reg);
>   	else
> -		val = *(adev->mes.read_val_ptr);
> +		val = *(read_val_ptr);
>   
>   error:
> +	if (addr_offset)
> +		amdgpu_device_wb_free(adev, addr_offset);
>   	return val;
>   }
>   
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.h
> index 45e3508f0f8e..83f45bb48427 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.h
> @@ -119,9 +119,6 @@ struct amdgpu_mes {
>   	uint32_t			query_status_fence_offs[AMDGPU_MAX_MES_PIPES];
>   	uint64_t			query_status_fence_gpu_addr[AMDGPU_MAX_MES_PIPES];
>   	uint64_t			*query_status_fence_ptr[AMDGPU_MAX_MES_PIPES];
> -	uint32_t                        read_val_offs;
> -	uint64_t			read_val_gpu_addr;
> -	uint32_t			*read_val_ptr;
>   
>   	uint32_t			saved_flags;
>