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authorDan Williams <dan.j.williams@intel.com>2020-01-30 23:06:07 +0300
committerDan Williams <dan.j.williams@intel.com>2020-02-21 03:58:55 +0300
commit9ffc1d19fc4a6dfcfe06c91c2861ad6d44fdd92d (patch)
tree5fb9d67b4b35ee457f8fc2d60695f6c6ed213e76 /lib
parent1d0827b75ee7df497f611a2ac412a88135fb0ef5 (diff)
downloadlinux-9ffc1d19fc4a6dfcfe06c91c2861ad6d44fdd92d.tar.xz
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')
-rw-r--r--lib/Kconfig3
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