[PATCH 03/13] drm/amdgpu/UAPI: add new CS chunk for GFX shadow buffers

[Marek Olšák]

That's not why it was removed. It was removed because userspace doesn't use
GDS memory and gds_va is always going to be 0.

Firmware shouldn't use it because using it would increase preemption
latency.

Marek

On Sun, Apr 9, 2023, 11:21 Christian König <ckoenig.leichtzumerken at gmail.com>
wrote:

> We removed the GDS information because they were unnecessary. The GDS size
> was already part of the device info before we added the shadow info.
>
> But as far as I know the firmware needs valid VAs for all three buffers or
> won't work correctly.
>
> Christian.
>
> Am 06.04.23 um 17:01 schrieb Marek Olšák:
>
> There is no GDS shadowing info in the device info uapi, so userspace can't
> create any GDS buffer and thus can't have any GDS va. It's a uapi issue,
> not what firmware wants to do.
>
> Marek
>
> On Thu, Apr 6, 2023 at 6:31 AM Christian König <
> ckoenig.leichtzumerken at gmail.com> wrote:
>
>> That's what I thought as well, but Mitch/Hans insisted on that.
>>
>> We should probably double check internally.
>>
>> Christian.
>>
>> Am 06.04.23 um 11:43 schrieb Marek Olšák:
>>
>> GDS memory isn't used on gfx11. Only GDS OA is used.
>>
>> Marek
>>
>> On Thu, Apr 6, 2023 at 5:09 AM Christian König <christian.koenig at amd.com>
>> wrote:
>>
>>> Why that?
>>>
>>> This is the save buffer for GDS, not the old style GDS BOs.
>>>
>>> Christian.
>>>
>>> Am 06.04.23 um 09:36 schrieb Marek Olšák:
>>>
>>> gds_va is unnecessary.
>>>
>>> Marek
>>>
>>> On Thu, Mar 30, 2023 at 3:18 PM Alex Deucher <alexander.deucher at amd.com>
>>> wrote:
>>>
>>>> For GFX11, the UMD needs to allocate some shadow buffers
>>>> to be used for preemption.  The UMD allocates the buffers
>>>> and passes the GPU virtual address to the kernel since the
>>>> kernel will program the packet that specified these
>>>> addresses as part of its IB submission frame.
>>>>
>>>> v2: UMD passes shadow init to tell kernel when to initialize
>>>>     the shadow
>>>>
>>>> Reviewed-by: Christian König <christian.koenig at amd.com>
>>>> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
>>>> ---
>>>>  include/uapi/drm/amdgpu_drm.h | 10 ++++++++++
>>>>  1 file changed, 10 insertions(+)
>>>>
>>>> diff --git a/include/uapi/drm/amdgpu_drm.h
>>>> b/include/uapi/drm/amdgpu_drm.h
>>>> index b6eb90df5d05..3d9474af6566 100644
>>>> --- a/include/uapi/drm/amdgpu_drm.h
>>>> +++ b/include/uapi/drm/amdgpu_drm.h
>>>> @@ -592,6 +592,7 @@ struct drm_amdgpu_gem_va {
>>>>  #define AMDGPU_CHUNK_ID_SCHEDULED_DEPENDENCIES 0x07
>>>>  #define AMDGPU_CHUNK_ID_SYNCOBJ_TIMELINE_WAIT    0x08
>>>>  #define AMDGPU_CHUNK_ID_SYNCOBJ_TIMELINE_SIGNAL  0x09
>>>> +#define AMDGPU_CHUNK_ID_CP_GFX_SHADOW   0x0a
>>>>
>>>>  struct drm_amdgpu_cs_chunk {
>>>>         __u32           chunk_id;
>>>> @@ -708,6 +709,15 @@ struct drm_amdgpu_cs_chunk_data {
>>>>         };
>>>>  };
>>>>
>>>> +#define AMDGPU_CS_CHUNK_CP_GFX_SHADOW_FLAGS_INIT_SHADOW         0x1
>>>> +
>>>> +struct drm_amdgpu_cs_chunk_cp_gfx_shadow {
>>>> +       __u64 shadow_va;
>>>> +       __u64 csa_va;
>>>> +       __u64 gds_va;
>>>> +       __u64 flags;
>>>> +};
>>>> +
>>>>  /*
>>>>   *  Query h/w info: Flag that this is integrated (a.h.a. fusion) GPU
>>>>   *
>>>> --
>>>> 2.39.2
>>>>
>>>>
>>>
>>
>
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