[Intel-xe] [PATCH 1/2] drm/xe: Set AE PTE bit if enabled on smem

[Nirmoy Das]

Hi Lucas,

On 7/22/2023 3:41 AM, Lucas De Marchi wrote:
> On Fri, Jul 21, 2023 at 06:41:57PM +0200, Nirmoy Das wrote:
>> Hi Lucas,
>>
>> On 7/21/2023 6:14 PM, Lucas De Marchi wrote:
>>> On Fri, Jul 21, 2023 at 04:07:44PM +0200, Nirmoy Das wrote:
>>>> Set AE PTE bit on smem if the platform is supported and
>>>> enabled device scoped atomics on system memory by a
>>>> user with madvise ioctl.
>>>>
>>>> Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
>>>> ---
>>>> drivers/gpu/drm/xe/xe_pt.c | 4 ++++
>>>> 1 file changed, 4 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/xe/xe_pt.c b/drivers/gpu/drm/xe/xe_pt.c
>>>> index 457f1363ec67..d43c91cf4776 100644
>>>> --- a/drivers/gpu/drm/xe/xe_pt.c
>>>> +++ b/drivers/gpu/drm/xe/xe_pt.c
>>>> @@ -774,6 +774,10 @@ xe_pt_stage_bind(struct xe_tile *tile, struct 
>>>> xe_vma *vma,
>>>>         xe_walk.dma_offset = vram_region_gpu_offset(bo->ttm.resource);
>>>>         xe_walk.cache = XE_CACHE_WB;
>>>>     } else {
>>>> +        if (tile_to_xe(tile)->info.platform != XE_PVC &&
>>>
>>> why the platform check?
>>
>>
>> PVC doesn't support atomics on smem. Should I move the check in the 
>> madvise ioctl instead ?
>
> yes, I think so. See below
>
>>
>> Regards,
>>
>> Nirmoy
>>
>>>
>>> Lucas De Marchi
>>>
>>>> +            (vma && vma->gpuva.flags & XE_VMA_ATOMIC_PTE_BIT))
>
> this check should suffice without adding each and every platform
> throughout the code. When we can't do a generic check, then we should
> add helper functions like has_xyz() to abstract what we are checking.


I see you what you meant. I will remove that platform check.

Should I add a check to return an error to userspace if a platform 
doesn't support device atomics ?


Thanks,

Nirmoy

>
> Lucas De Marchi
>
>>>> +            xe_walk.default_pte |= XE_USM_PPGTT_PTE_AE;
>>>> +
>>>>         if (!xe_vma_has_no_bo(vma) && bo->flags & XE_BO_SCANOUT_BIT)
>>>>             xe_walk.cache = XE_CACHE_WT;
>>>>         else
>>>> -- 
>>>> 2.39.0
>>>>