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__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)
