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

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