Re: [PATCH v2] memblock: add no-map alloc functions

[DaeRo Lee <skseofh@gmail.com>]

2024년 4월 28일 (일) 오후 9:01, Mike Rapoport <rppt@kernel.org>님이 작성:
>
> On Sun, Apr 28, 2024 at 07:36:40PM +0900, DaeRo Lee wrote:
> > 2024년 4월 28일 (일) 오후 3:35, Mike Rapoport <rppt@kernel.org>님이 작성:
> > >
> > > On Sat, Apr 27, 2024 at 07:24:23PM +0900, DaeRo Lee wrote:
> > > > 2024년 4월 27일 (토) 오후 5:50, Mike Rapoport <rppt@kernel.org>님이 작성:
> > > > > > >
> > > > > > > So, here is what I think:
> > > > > > > - reserved-memory w/ nomap region -> mark only to memblock.memory
> > > > > > > - reserved-memory w/o nomap region -> add to the memblock.reserved
> > > > >
> > > > > NOMAP and memblock.reserved are semantically different, and at makes sense
> > > > > to have a "reserved nomap" node in fdt recorded in both memblock.memory and
> > > > > memblock.reserved.
> > > > >
> > > > > memblock.reserved represents the memory that is used by firmware or early
> > > > > kernel allocation, so reserved memory in fdt should be reserved in memblock
> > > > > as well. I believe it's an oversight that early_init_dt_reserve_memory()
> > > > > does not call memblock_reserve() for nomap memory.
> > > > >
> > > > > NOMAP is a property of a memory region that says that that region should
> > > > > not be mapped in the linear map, it's not necessarily in use.
> > > >
> > > > I agree that the NOMAP region should be added to memblock.reserved.
> > > >
> > > > So, I think we need to clean-up memmap_init_reserved_pages, because in
> > > > this function we call reserve_bootmem_region for memblock.reserved and
> > > > memblock.memory with nomap. We don't need to call
> > > > reserve_bootmem_region for nomap.
> > >
> > > Read the comment about memblock_mark_nomap()
> > I read the comment about memblock_mark_nomap() and understood that
> > regions with nomap flags should be treated as PageReserved.
> > But, if we add this nomap region to memblock.reserved, the region with
> > nomap flag will be processed in the first for-loop in
> > memmap_init_reserved_pages.
>
> memblock still must make sure that pages in nomap regions get PG_Reserved
> to be robust against potential errors and bugs in firmware parsing.
Got it.
Thank you for your comments. I'll make another patch for just clean-up
early_init_dt_reserve_memory()

Thank you.

Regards,
DaeRo Lee