On Wed, 7 Jan 2026 20:18:12 +1100 Jordan Niethe <[email protected]> wrote:
> Today, when creating these device private struct pages, the first step > is to use request_free_mem_region() to get a range of physical address > space large enough to represent the devices memory. This allocated > physical address range is then remapped as device private memory using > memremap_pages. Welcome to Linux MM. That's a heck of an opening salvo ;) > Needing allocation of physical address space has some problems: > > 1) There may be insufficient physical address space to represent the > device memory. KASLR reducing the physical address space and VM > configurations with limited physical address space increase the > likelihood of hitting this especially as device memory increases. This > has been observed to prevent device private from being initialized. > > 2) Attempting to add the device private pages to the linear map at > addresses beyond the actual physical memory causes issues on > architectures like aarch64 - meaning the feature does not work there > [0]. Can you better help us understand the seriousness of these problems? How much are our users really hurting from this? > Seeking opinions on using the mpfns like this or if a new type would be > preferred. Whose opinions? IOW, can you suggest who you'd like to see review this work? > > * NOTE: I will need help in testing the driver changes * > Again, please name names ;) I'm not afraid to prod. I'm reluctant to add this to mm.git's development/testing branches at this time. Your advice on when you think we're ready for that step would be valuable, thanks.
