Re: [PATCH] Increase AMDGPU_MAX_UVD_INSTANCES to 3

[James Zhu <jamesz-5C7GfCeVMHo@public.gmane.org>]

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On 2018-06-25 02:53 PM, Alex Deucher wrote:
> On Mon, Jun 25, 2018 at 2:37 PM, James Zhu <jamesz-5C7GfCeVMHo@public.gmane.org> wrote:
>> For one UVD instance case,:
>>
>>
>> In function amdgpu_driver_load_kms, all ring->me should be set to zero.
>>      adev = kzalloc(sizeof(struct amdgpu_device), GFP_KERNEL);
>>
>>
>> For two UVD instances cases:
>>
>> static void uvd_v7_0_set_ring_funcs(struct amdgpu_device *adev)
>> ..
>>      for (i = 0; i < adev->uvd.num_uvd_inst; i++) {
>>          adev->uvd.inst[i].ring.me = i;
>>
>> static void uvd_v7_0_set_enc_ring_funcs(struct amdgpu_device *adev)
>>
>>      for (j = 0; j < adev->uvd.num_uvd_inst; j++) {
>>              adev->uvd.inst[j].ring_enc[i].me = j;
>>
>> uvd_v4_2_early_init in uvd_v4_2.c  adev->uvd.num_uvd_inst = 1;
>> uvd_v5_0_early_init in uvd_v5_0.c  adev->uvd.num_uvd_inst = 1;
>> uvd_v6_0_early_init in uvd_v6_0.c  adev->uvd.num_uvd_inst = 1;
>> uvd_v7_0_early_init in uvd_v7_0.c
>>      if (adev->asic_type == CHIP_VEGA20)
>>          adev->uvd.num_uvd_inst = UVD7_MAX_HW_INSTANCES_VEGA20;/*2*/
>>      else
>>          adev->uvd.num_uvd_inst = 1;
>>
>>
>> I didn't know when ring->me is set to 2. Maybe there is some leakage
>> somewhere.
>>
> What about older uvd (4.2, 5.0, 6.0) blocks?
I think the below code will reset 
adev->uvd.inst[AMDGPU_MAX_UVD_INSTANCES].ring->me and
adev->uvd.inst[AMDGPU_MAX_UVD_INSTANCES].ring_enc[AMDGPU_MAX_UVD_ENC_RINGS]->me 
to zero.
for older uvd IP UVD block.

/*adev = kzalloc(sizeof(struct amdgpu_device), GFP_KERNEL); */Do I 
understand correctly? James/**/

>
> Alex
>
>> Best regards!
>>
>> James zhu
>>
>>
>> On 2018-06-25 01:29 PM, Deucher, Alexander wrote:
>>
>> Odd. The structure should be 0 initialized.  Does this patch help?
>>
>>
>> Alex
>>
>> ________________________________
>> From: Timothy Pearson <tpearson-z0qzliK6Om0mgXJStvpl+vpXobYPEAuW@public.gmane.org>
>> Sent: Monday, June 25, 2018 11:53:12 AM
>> To: Zhu, James
>> Cc: amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org; Deucher, Alexander; Zhou,
>> David(ChunMing); Koenig, Christian
>> Subject: Re: [PATCH] Increase AMDGPU_MAX_UVD_INSTANCES to 3
>>
>> n 06/25/2018 09:46 AM, James Zhu wrote:
>>>
>>> On 2018-06-23 08:02 PM, Timothy Pearson wrote:
>>>> amdgpu_fence_driver_start_ring() attempts to access
>>>> UVD instance 2 during setup, while the existing UVD
>>>> instance count only allows instances 0 and 1.
>>>>
>>>> Increase AMDGPU_MAX_UVD_INSTANCES by one to avoid the
>>>> invalid array access.
>>>>
>>>> Caught by UBSAN.
>>> Hi Timothy,
>>>
>>>  From design of view, it is not right to just change
>>> AMDGPU_MAX_UVD_INSTANCES to 3.
>>>
>>> Could you tell me some detail of UBSAN test and attach the dmesg also?
>> Definitely, was looking for some feedback from anyone knowing more about
>> the internals of the UVD system.
>>
>> What's happening is that "ring->me" in amdgpu_fence_driver_start_ring()
>> (drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c:379) is set to a value of
>> "2".  The overall dmesg is otherwise uninteresting, but I can try to
>> grab the UBSAN output if needed.
>>
>> --
>> Timothy Pearson
>> Raptor Engineering
>> +1 (415) 727-8645 (direct line)
>> +1 (512) 690-0200 (switchboard)
>> https://www.raptorengineering.com
>>
>>
>>
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>>


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