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| author | Dan Williams <dan.j.williams@intel.com> | 2020-01-30 12:06:07 -0800 |
|---|---|---|
| committer | Dan Williams <dan.j.williams@intel.com> | 2020-02-20 16:58:55 -0800 |
| commit | 9ffc1d19fc4a6dfcfe06c91c2861ad6d44fdd92d (patch) | |
| tree | 5fb9d67b4b35ee457f8fc2d60695f6c6ed213e76 /lib/Kconfig | |
| parent | 1d0827b75ee7df497f611a2ac412a88135fb0ef5 (diff) | |
| download | lwn-9ffc1d19fc4a6dfcfe06c91c2861ad6d44fdd92d.tar.gz lwn-9ffc1d19fc4a6dfcfe06c91c2861ad6d44fdd92d.zip | |
mm/memremap_pages: Introduce memremap_compat_align()
The "sub-section memory hotplug" facility allows memremap_pages() users
like libnvdimm to compensate for hardware platforms like x86 that have a
section size larger than their hardware memory mapping granularity. The
compensation that sub-section support affords is being tolerant of
physical memory resources shifting by units smaller (64MiB on x86) than
the memory-hotplug section size (128 MiB). Where the platform
physical-memory mapping granularity is limited by the number and
capability of address-decode-registers in the memory controller.
While the sub-section support allows memremap_pages() to operate on
sub-section (2MiB) granularity, the Power architecture may still
require 16MiB alignment on "!radix_enabled()" platforms.
In order for libnvdimm to be able to detect and manage this per-arch
limitation, introduce memremap_compat_align() as a common minimum
alignment across all driver-facing memory-mapping interfaces, and let
Power override it to 16MiB in the "!radix_enabled()" case.
The assumption / requirement for 16MiB to be a viable
memremap_compat_align() value is that Power does not have platforms
where its equivalent of address-decode-registers never hardware remaps a
persistent memory resource on smaller than 16MiB boundaries. Note that I
tried my best to not add a new Kconfig symbol, but header include
entanglements defeated the #ifndef memremap_compat_align design pattern
and the need to export it defeats the __weak design pattern for arch
overrides.
Based on an initial patch by Aneesh.
Link: http://lore.kernel.org/r/CAPcyv4gBGNP95APYaBcsocEa50tQj9b5h__83vgngjq3ouGX_Q@mail.gmail.com
Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reported-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'lib/Kconfig')
| -rw-r--r-- | lib/Kconfig | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/lib/Kconfig b/lib/Kconfig index bc7e56370129..5d53f9609c25 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -615,6 +615,9 @@ config ARCH_HAS_PMEM_API config MEMREGION bool +config ARCH_HAS_MEMREMAP_COMPAT_ALIGN + bool + # use memcpy to implement user copies for nommu architectures config UACCESS_MEMCPY bool |