Re: [PATCH v8 06/25] gpu: nova-core: mm: Add support to use PRAMIN windows to write to VRAM

["Alexandre Courbot" <acourbot@nvidia.com>]

On Wed Feb 25, 2026 at 7:53 AM JST, Joel Fernandes wrote:
> PRAMIN apertures are a crucial mechanism to direct read/write to VRAM.
> Add support for the same.

A few design thoughts that are not immediately actionable, but might
become this cycle if we get a tag with the new `Io` work.

Basically this feature is a prime candidate for an `Io` implementation.
It maps onto the BAR, has a fixed 1MB size, and needs to be accessed
using various sizes. It is also used to fill structured values, which
the I/O projection work will also allow us to do.

The current design doesn't allow the user to explicitly set the start of
the sliding window - this results in a sub-optimal usage of the hardware
and more complex code in this module. At this level, we just want
something that exposes the hardware as it is, i.e. "give me a view of
the 1MB of VRAM starting from this 64K-aligned address".

Then on top of that we can implement another type that handles the
window automatically if we want, but I don't think we will actually need
it. The page table code will most likely want to set the window to the
start of its structure, project it, and access it using compile-time
checked offsets.

If that turns out to be insufficient, we can always compose something
more complex from this basic piece - but the base `Pramin` should stay
simple and truthful to the underlying hardware IMHO.