Re: [RFC PATCH 0/6] Remove device private pages from physical address space

Matthew Wilcox
2025-11-28T15:09:46Z

On Fri, Nov 28, 2025 at 03:41:40PM +1100, Jordan Niethe wrote:
> A consequence of placing the device private pages outside of the
> physical address space is that they no longer have a PFN. However, it is
> still necessary to be able to look up a corresponding device private
> page from a device private PTE entry, which means that we still require
> some way to index into this device private address space. This leads to
> the idea of a device private PFN. This is like a PFN but instead of

Don't call it a "device private PFN". That's going to lead to
confusion. Device private index? Device memory index?

> By removing the device private pages from the physical address space,
> this RFC also opens up the possibility to moving away from tracking
> device private memory using struct pages in the future. This is
> desirable as on systems with large amounts of memory these device
> private struct pages use a signifiant amount of memory and take a
> significant amount of time to initialize.

I did tell Jerome he was making a huge mistake with his design, but
he forced it in anyway.