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

[Li, Chong(Alan)]

[AMD Official Use Only - AMD Internal Distribution Only]

Hi, Christian.

the variable "addr_offset" need to initialize as 0,
since when function "amdgpu_device_wb_get" failed,
if "addr_offset" is not 0, function "amdgpu_device_wb_free" will free the wb.

I will do not initialize the variable "read_val_ptr" and "read_val_gpu_addr".


> +     uint32_t addr_offset = 0;
> +     uint64_t read_val_gpu_addr = 0;
> +     uint32_t *read_val_ptr = NULL;

> +     if (amdgpu_device_wb_get(adev, &addr_offset)) {
> +             DRM_ERROR("critical bug! too many mes readers\n");
> +             goto error;
> +     }

>   error:
> +     if (addr_offset)
> +             amdgpu_device_wb_free(adev, addr_offset);




Thanks,
Chong.

-----Original Message-----
From: Koenig, Christian <Christian.Koenig at amd.com>
Sent: Tuesday, November 5, 2024 4:52 PM
To: Li, Chong(Alan) <Chong.Li at amd.com>; amd-gfx at lists.freedesktop.org
Cc: Deng, Emily <Emily.Deng at amd.com>; cao, lin <lin.cao at amd.com>; Andjelkovic, Dejan <Dejan.Andjelkovic at amd.com>; Yin, ZhenGuo (Chris) <ZhenGuo.Yin at amd.com>
Subject: Re: [PATCH] drm/amdgpu: fix return random value when multiple threads read registers via mes.

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 at 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;
>