Re: [PATCH 1/1] drm/amdgpu: Flush TLB after mapping for VG20+XGMI

[Paul Menzel <pmenzel@xxxxxxxxxxxxx>]

Dear Philip,


Thank you for your patch.

Am 01.04.22 um 21:57 schrieb Philip Yang:
> For VG20 + XGMI bridge, all mappings PTEs cache in TC, this may have
> stall invalid PTEs in TC because one cache line has 8 pages. Need always

Can you please rephrase. “may have stall …” is really hard to understand.

> flush_tlb after updating mapping.

Maybe:

So, always flush_tlb after updating the mapping.

> Signed-off-by: Philip Yang <Philip.Yang@xxxxxxx>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index f0aec04111a3..687c9a140645 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -837,6 +837,12 @@ int amdgpu_vm_update_range(struct amdgpu_device *adev, struct amdgpu_vm *vm,
>   		goto error_unlock;
>   	}
>   
> +	/* Vega20+XGMI where PTEs get inadvertently cached in L2 texture cache,
> +	 * heavy-weight flush TLB unconditionally.
> +	 */
> +	flush_tlb |= (adev->gmc.xgmi.num_physical_nodes &&
> +		      adev->ip_versions[GC_HWIP][0] == IP_VERSION(9, 4, 0));
> +
>   	memset(&params, 0, sizeof(params));
>   	params.adev = adev;
>   	params.vm = vm;

Did you do any performance measurement, if that flushing affects anything?


Kind regards,

Paul