Dan Williams <dan.j.willi...@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.
Reviewed-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com> > > Link: > http://lore.kernel.org/r/capcyv4gbgnp95apyabcsocea50tqj9b5h__83vgngjq3oug...@mail.gmail.com > Reported-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com> > Reported-by: Jeff Moyer <jmo...@redhat.com> > Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org> > Cc: Paul Mackerras <pau...@samba.org> > Cc: Michael Ellerman <m...@ellerman.id.au> > Signed-off-by: Dan Williams <dan.j.willi...@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(-) > > 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 > diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c > index b94f7a7e94b8..a5c25cb87116 100644 > --- a/drivers/nvdimm/pfn_devs.c > +++ b/drivers/nvdimm/pfn_devs.c > @@ -750,7 +750,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn) > start = nsio->res.start; > size = resource_size(&nsio->res); > npfns = PHYS_PFN(size - SZ_8K); > - align = max(nd_pfn->align, (1UL << SUBSECTION_SHIFT)); > + align = max(nd_pfn->align, SUBSECTION_SIZE); > end_trunc = start + size - ALIGN_DOWN(start + size, align); > if (nd_pfn->mode == PFN_MODE_PMEM) { > /* > diff --git a/include/linux/io.h b/include/linux/io.h > index 35e8d84935e0..ccd34519fad3 100644 > --- a/include/linux/io.h > +++ b/include/linux/io.h > @@ -6,6 +6,7 @@ > #ifndef _LINUX_IO_H > #define _LINUX_IO_H > > +#include <linux/mmzone.h> > #include <linux/types.h> > #include <linux/init.h> > #include <linux/bug.h> > @@ -79,6 +80,28 @@ void *devm_memremap(struct device *dev, resource_size_t > offset, > size_t size, unsigned long flags); > void devm_memunmap(struct device *dev, void *addr); > > +#ifndef memremap_compat_align > +#ifdef CONFIG_SPARSEMEM > +/* > + * Minimum compatible alignment of the resource (start, end) across > + * memremap interfaces (i.e. memremap + memremap_pages) > + */ > +static inline unsigned long memremap_compat_align(void) > +{ > + return SUBSECTION_SIZE; > +} > +#else /* CONFIG_SPARSEMEM */ > +/* > + * No ZONE_DEVICE / memremap_pages() support so the minimum mapping > + * granularity is a single page. > + */ > +static inline unsigned long memremap_compat_align(void) > +{ > + return PAGE_SIZE; > +} > +#endif /* CONFIG_SPARSEMEM */ > +#endif /* memremap_compat_align */ > + > #ifdef CONFIG_PCI > /* > * The PCI specifications (Rev 3.0, 3.2.5 "Transaction Ordering and > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 89d8ff06c9ce..b0de83620cd7 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -1171,6 +1171,7 @@ static inline unsigned long section_nr_to_pfn(unsigned > long sec) > #define SECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SECTION_MASK) > > #define SUBSECTION_SHIFT 21 > +#define SUBSECTION_SIZE (1UL << SUBSECTION_SHIFT) > > #define PFN_SUBSECTION_SHIFT (SUBSECTION_SHIFT - PAGE_SHIFT) > #define PAGES_PER_SUBSECTION (1UL << PFN_SUBSECTION_SHIFT)
