Messages in this thread |  | | From | Michael Ellerman <> | Subject | Re: [PATCH 2/5] mm/memremap_pages: Introduce memremap_compat_align() | Date | Wed, 05 Feb 2020 14:05:02 +1100 |
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Dan Williams <dan.j.williams@intel.com> writes: > 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. > > 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> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Signed-off-by: Dan Williams <dan.j.williams@intel.com> > --- > arch/powerpc/include/asm/io.h | 10 ++++++++++ > drivers/nvdimm/pfn_devs.c | 2 +- > include/linux/io.h | 23 +++++++++++++++++++++++ > include/linux/mmzone.h | 1 + > 4 files changed, 35 insertions(+), 1 deletion(-)
The powerpc change here looks fine to me.
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
cheers
> diff --git a/arch/powerpc/include/asm/io.h b/arch/powerpc/include/asm/io.h > index a63ec938636d..0fa2dc483008 100644 > --- a/arch/powerpc/include/asm/io.h > +++ b/arch/powerpc/include/asm/io.h > @@ -734,6 +734,16 @@ extern void __iomem * __ioremap_at(phys_addr_t pa, void *ea, > unsigned long size, pgprot_t prot); > extern void __iounmap_at(void *ea, unsigned long size); > > +#ifdef CONFIG_SPARSEMEM > +static inline unsigned long memremap_compat_align(void) > +{ > + if (radix_enabled()) > + return SUBSECTION_SIZE; > + return (1UL << mmu_psize_defs[mmu_linear_psize].shift); > +} > +#define memremap_compat_align memremap_compat_align > +#endif > + > /* > * When CONFIG_PPC_INDIRECT_PIO is set, we use the generic iomap implementation > * which needs some additional definitions here. They basically allow PIO
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