Re: [PATCH v4 0/4] arm64: drop pfn_valid_within() and simplify pfn_valid()
From: Mike Rapoport
Date: Wed May 12 2021 - 03:34:30 EST
On Wed, May 12, 2021 at 09:00:02AM +0200, Ard Biesheuvel wrote:
> On Tue, 11 May 2021 at 12:05, Mike Rapoport <rppt@xxxxxxxxxx> wrote:
> > From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> > Hi,
> > These patches aim to remove CONFIG_HOLES_IN_ZONE and essentially hardwire
> > pfn_valid_within() to 1.
> > The idea is to mark NOMAP pages as reserved in the memory map and restore
> > the intended semantics of pfn_valid() to designate availability of struct
> > page for a pfn.
> > With this the core mm will be able to cope with the fact that it cannot use
> > NOMAP pages and the holes created by NOMAP ranges within MAX_ORDER blocks
> > will be treated correctly even without the need for pfn_valid_within.
> > The patches are boot tested on qemu-system-aarch64.
> Did you use EFI boot when testing this? The memory map is much more
> fragmented in that case, so this would be a good data point.
Right, something like this:
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000040000000-0x00000000ffffbfff]
[ 0.000000] node 0: [mem 0x00000000ffffc000-0x00000000ffffffff]
[ 0.000000] node 0: [mem 0x0000000100000000-0x00000004386fffff]
[ 0.000000] node 0: [mem 0x0000000438700000-0x000000043899ffff]
[ 0.000000] node 0: [mem 0x00000004389a0000-0x00000004389bffff]
[ 0.000000] node 0: [mem 0x00000004389c0000-0x0000000438b5ffff]
[ 0.000000] node 0: [mem 0x0000000438b60000-0x000000043be3ffff]
[ 0.000000] node 0: [mem 0x000000043be40000-0x000000043becffff]
[ 0.000000] node 0: [mem 0x000000043bed0000-0x000000043bedffff]
[ 0.000000] node 0: [mem 0x000000043bee0000-0x000000043bffffff]
[ 0.000000] node 0: [mem 0x000000043c000000-0x000000043fffffff]
This is a pity really, because I don't see a fundamental reason for those
tiny holes all over the place.
I know that EFI/ACPI mandates "IO style" memory access for those regions,
but I fail to get why...
> > I beleive it would be best to route these via mmotm tree.
> > v4:
> > * rebase on v5.13-rc1
> > v3: Link: https://lore.kernel.org/lkml/20210422061902.21614-1-rppt@xxxxxxxxxx
> > * Fix minor issues found by Anshuman
> > * Freshen up the declaration of pfn_valid() to make it consistent with
> > pfn_is_map_memory()
> > * Add more Acked-by and Reviewed-by tags, thanks Anshuman and David
> > v2: Link: https://lore.kernel.org/lkml/20210421065108.1987-1-rppt@xxxxxxxxxx
> > * Add check for PFN overflow in pfn_is_map_memory()
> > * Add Acked-by and Reviewed-by tags, thanks David.
> > v1: Link: https://lore.kernel.org/lkml/20210420090925.7457-1-rppt@xxxxxxxxxx
> > * Add comment about the semantics of pfn_valid() as Anshuman suggested
> > * Extend comments about MEMBLOCK_NOMAP, per Anshuman
> > * Use pfn_is_map_memory() name for the exported wrapper for
> > memblock_is_map_memory(). It is still local to arch/arm64 in the end
> > because of header dependency issues.
> > rfc: Link: https://lore.kernel.org/lkml/20210407172607.8812-1-rppt@xxxxxxxxxx
> > Mike Rapoport (4):
> > include/linux/mmzone.h: add documentation for pfn_valid()
> > memblock: update initialization of reserved pages
> > arm64: decouple check whether pfn is in linear map from pfn_valid()
> > arm64: drop pfn_valid_within() and simplify pfn_valid()
> > arch/arm64/Kconfig | 3 ---
> > arch/arm64/include/asm/memory.h | 2 +-
> > arch/arm64/include/asm/page.h | 3 ++-
> > arch/arm64/kvm/mmu.c | 2 +-
> > arch/arm64/mm/init.c | 14 +++++++++++++-
> > arch/arm64/mm/ioremap.c | 4 ++--
> > arch/arm64/mm/mmu.c | 2 +-
> > include/linux/memblock.h | 4 +++-
> > include/linux/mmzone.h | 11 +++++++++++
> > mm/memblock.c | 28 ++++++++++++++++++++++++++--
> > 10 files changed, 60 insertions(+), 13 deletions(-)
> > base-commit: 6efb943b8616ec53a5e444193dccf1af9ad627b5
> > --
> > 2.28.0