Re: [PATCH v1 0/3] vfio/nvgrace-gpu: Enable grace blackwell boards

[Ankit Agrawal]

>>
>> NVIDIA's recently introduced Grace Blackwell (GB) Superchip in
>> continuation with the Grace Hopper (GH) superchip that provides a
>> cache coherent access to CPU and GPU to each other's memory with
>> an internal proprietary chip-to-chip (C2C) cache coherent interconnect.
>> The in-tree nvgrace-gpu driver manages the GH devices. The intention
>> is to extend the support to the new Grace Blackwell boards.
>
> Where do we stand on QEMU enablement of GH, or the GB support here?
> IIRC, the nvgrace-gpu variant driver was initially proposed with QEMU
> being the means through which the community could make use of this
> driver, but there seem to be a number of pieces missing for that
> support.  Thanks,
> 
> Alex

Hi Alex, the Qemu enablement changes for GH is already in Qemu 9.0.
This is the Generic initiator change that got merged:
https://lore.kernel.org/all/20240308145525.10886-1-ankita@xxxxxxxxxx/

The missing pieces are actually in the kvm/kernel viz:
1. KVM need to map the device memory as Normal. The KVM patch was
proposed here. This patch need refresh to address the suggestions:
https://lore.kernel.org/all/20230907181459.18145-2-ankita@xxxxxxxxxx/
2. ECC handling series for the GPU device memory that is remap_pfn_range()
mapped: https://lore.kernel.org/all/20231123003513.24292-1-ankita@xxxxxxxxxx/

With those changes, the GH would be functional with the Qemu 9.0.
We discovered a separate Qemu issue while doing verification of Grace Blackwell,
where the 512G of highmem proved short here:
https://github.com/qemu/qemu/blob/v9.0.0/hw/arm/virt.c#L211
We are planning to have a proposal for the fix floated for that.

Thanks
Ankit Agrawal