Graceful page fault handling for Vega/Navi

[Kuehling, Felix]

On 2019-09-04 11:02 a.m., Christian König wrote:
> Hi everyone,
>
> this series is the next puzzle piece for recoverable page fault handling on Vega and Navi.
>
> It adds a new direct scheduler entity for VM updates which is then used to update page tables during a fault.
>
> In other words previously an application doing an invalid memory access would just hang and/or repeat the invalid access over and over again. Now the handling is modified so that the invalid memory access is redirected to the dummy page.
>
> This needs the following prerequisites:
> a) The firmware must be new enough so allow re-routing of page faults.
> b) Fault retry must be enabled using the amdgpu.noretry=0 parameter.
> c) Enough free VRAM to allocate page tables to point to the dummy page.
>
> The re-routing of page faults current only works on Vega10, so Vega20 and Navi will still need some more time.

Wait, we don't do the page fault rerouting on Vega20 yet? So we're 
getting the full brunt of the fault storm on the main interrupt ring? In 
that case, we should probably change the default setting of 
amdgpu.noretry=1 at least until that's done.

Other than that the patch series looks reasonable to me. I commented on 
patches 4 and 9 separately.

Patch 1 is Acked-by: Felix Kuehling <Felix.Kuehling at amd.com>

With the issues addressed that I pointed out, the rest is

Reviewed-by: Felix Kuehling <Felix.Kuehling at amd.com>

Regards,
   Felix


> Please review and/or comment,
> Christian.
>
>
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