Re: [PATCH RFC v6 05/26] nova-core: mm: Add support to use PRAMIN windows to write to VRAM

John Hubbard
2026-01-30T01:12:19Z

On 1/29/26 4:26 PM, Joel Fernandes wrote:
> Hi, Danilo, all,
>
> Based on the below discussion and research, I came up with some deadlock
> scenarios that we need to handle in the v6 series of these patches. Please let
> me know if I missed something below. At the moment, off the top I identified
> that we are doing GFP_KERNEL memory allocations inside GPU buddy allocator
> during map/unmap. I will work on solutions for that. Thanks.
>
> All deadlock scenarios
> ----------------------
> The gist is, in the DMA fence signaling critical path we cannot acquire
> resources (locks or memory allocation etc) that are already acquired when a
> fence is being waited on to be signaled. So we have to careful which resources
> we acquire, and also we need to be careful which paths in the driver we do any
> memory allocations under locks that we need in the dma-fence signaling critical
> path (when doing the virtual memory map/unmap)

unmap? Are you seeing any allocations happening during unmap? I don't
immediately see any, but that sounds surprising.

thanks,
--
John Hubbard