diff options
| 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 /include/linux/memremap.h | |
| parent | 1d0827b75ee7df497f611a2ac412a88135fb0ef5 (diff) | |
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 'include/linux/memremap.h')
| -rw-r--r-- | include/linux/memremap.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/include/linux/memremap.h b/include/linux/memremap.h index 6fefb09af7c3..8af1cbd8f293 100644 --- a/include/linux/memremap.h +++ b/include/linux/memremap.h @@ -132,6 +132,7 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn, unsigned long vmem_altmap_offset(struct vmem_altmap *altmap); void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns); +unsigned long memremap_compat_align(void); #else static inline void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) @@ -165,6 +166,12 @@ static inline void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns) { } + +/* when memremap_pages() is disabled all archs can remap a single page */ +static inline unsigned long memremap_compat_align(void) +{ + return PAGE_SIZE; +} #endif /* CONFIG_ZONE_DEVICE */ static inline void put_dev_pagemap(struct dev_pagemap *pgmap) @@ -172,4 +179,5 @@ static inline void put_dev_pagemap(struct dev_pagemap *pgmap) if (pgmap) percpu_ref_put(pgmap->ref); } + #endif /* _LINUX_MEMREMAP_H_ */ |