On Mon, Mar 01, 2021 at 09:33:18AM +0100, Christoph Hellwig wrote:

Hi all,

i915 has some reason to want to avoid the track_pfn_remap overhead in remap_pfn_range. Add a function to the core VM to do just that rather than reinventing the functionality poorly in the driver.

It's not _notrack it's "rely on the tracking established by the struct io_mapping". Exporting a _notrack version to drivers sounds like not something we want to ever do. So I think you want a helper which takes the io_mapping, and not something that encourages drivers to go full stupid.

Note that the remap_io_sg path does get exercises when using Xorg on my Thinkpad X1, so this should be considered lightly tested, I've not managed to hit the remap_io_mapping path at all.

Needs an older machine and old userspace. intel-gfx CI should still check whether it's all ok. -Daniel