[amdgpu] Is it possible to disable page tables and use the physical address directly in amdgpu

[Smith John]

 Hi Christian,
Thanks for your reply. I agree with you that the VMID0 is special and
remapping is important. I was not sure if different VIMDs could have
different settings, such as enable/disable page tables.
Or to put it another way, I was wondering if the hardware supports purely
physical addressing like the real mode in CPUs, or page tables are
essential for the hardware.
More specifically, assuming it supports "real mode", to copy things from A
to B, one could allocate rings which are accessible by MMIO and fill sdma
packets using physical address to transfer data.

Regards,
Smith

Christian König <ckoenig.leichtzumerken at gmail.com> 于2020年12月1日周二 下午5:50写道：

> Am 01.12.20 um 07:58 schrieb Smith John:
>
> Hello!
> I was trying to figure out the impact of gpu page tables on applications'
> performance. I noticed that there are 16 vmids supported by the hardware *Vega
> 10*. Is it possible to use physical address directly in some vmids, or
> use physical address globally?
>
>
> No. VMID0 is used by the kernel for jobs like copying things from A to B
> and even there we use the VM remapping functionality.
>
> Regards,
> Christian.
>
>
>
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