On Tue, Jul 22, 2025 at 10:49:10AM +1000, Alistair Popple wrote: > > So what is it? > > IMHO a hack, because obviously we shouldn't require real physical addresses > for > something the CPU can't actually address anyway and this causes real > problems
IMHO what DEVICE PRIVATE really boils down to is a way to have swap entries that point to some kind of opaque driver managed memory. We have alot of assumptions all over about pfn/phys to page relationships so anything that has a struct page also has to come with a fake PFN today.. > (eg. it doesn't actually work on anything other than x86_64). There's no > reason > the "PFN" we store in device-private entries couldn't instead just be an index > into some data structure holding pointers to the struct pages. So instead of > using pfn_to_page()/page_to_pfn() we would use device_private_index_to_page() > and page_to_device_private_index(). It could work, but any of the pfn conversions would have to be tracked down.. Could be troublesome. Jason
