On Fri, Feb 14, 2020 at 12:59 PM Jeff Moyer <jmo...@redhat.com> wrote: > > Dan Williams <dan.j.willi...@intel.com> writes: > > > On Thu, Feb 13, 2020 at 8:58 AM Jeff Moyer <jmo...@redhat.com> wrote: > > >> I have just a couple of questions. > >> > >> First, can you please add a comment above the generic implementation of > >> memremap_compat_align describing its purpose, and why a platform might > >> want to override it? > > > > Sure, how about: > > > > /* > > * The memremap() and memremap_pages() interfaces are alternately used > > * to map persistent memory namespaces. These interfaces place different > > * constraints on the alignment and size of the mapping (namespace). > > * memremap() can map individual PAGE_SIZE pages. memremap_pages() can > > * only map subsections (2MB), and at least one architecture (PowerPC) > > * the minimum mapping granularity of memremap_pages() is 16MB. > > * > > * The role of memremap_compat_align() is to communicate the minimum > > * arch supported alignment of a namespace such that it can freely > > * switch modes without violating the arch constraint. Namely, do not > > * allow a namespace to be PAGE_SIZE aligned since that namespace may be > > * reconfigured into a mode that requires SUBSECTION_SIZE alignment. > > */ > > Well, if we modify the x86 variant to be PAGE_SIZE, I think that text > won't work. How about:
...but I'm not looking to change it to PAGE_SIZE, I'm going to fix the alignment check to skip if the namespace has "inner" alignment padding, i.e. "start_pad" and/or "end_trunc" are non-zero.
