From 92281dee825f6d2eb07c441437e4196a44b0861c Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Mon, 10 Aug 2015 23:07:06 -0400 Subject: arch: introduce memremap() Existing users of ioremap_cache() are mapping memory that is known in advance to not have i/o side effects. These users are forced to cast away the __iomem annotation, or otherwise neglect to fix the sparse errors thrown when dereferencing pointers to this memory. Provide memremap() as a non __iomem annotated ioremap_*() in the case when ioremap is otherwise a pointer to cacheable memory. Empirically, ioremap_() call sites are seeking memory-like semantics (e.g. speculative reads, and prefetching permitted). memremap() is a break from the ioremap implementation pattern of adding a new memremap_() for each mapping type and having silent compatibility fall backs. Instead, the implementation defines flags that are passed to the central memremap() and if a mapping type is not supported by an arch memremap returns NULL. We introduce a memremap prototype as a trivial wrapper of ioremap_cache() and ioremap_wt(). Later, once all ioremap_cache() and ioremap_wt() usage has been removed from drivers we teach archs to implement arch_memremap() with the ability to strictly enforce the mapping type. Cc: Arnd Bergmann Reviewed-by: Christoph Hellwig Signed-off-by: Dan Williams --- kernel/memremap.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) create mode 100644 kernel/memremap.c (limited to 'kernel/memremap.c') diff --git a/kernel/memremap.c b/kernel/memremap.c new file mode 100644 index 000000000000..a293de52e837 --- /dev/null +++ b/kernel/memremap.c @@ -0,0 +1,98 @@ +/* + * Copyright(c) 2015 Intel Corporation. All rights reserved. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of version 2 of the GNU General Public License as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + */ +#include +#include +#include + +#ifndef ioremap_cache +/* temporary while we convert existing ioremap_cache users to memremap */ +__weak void __iomem *ioremap_cache(resource_size_t offset, unsigned long size) +{ + return ioremap(offset, size); +} +#endif + +/** + * memremap() - remap an iomem_resource as cacheable memory + * @offset: iomem resource start address + * @size: size of remap + * @flags: either MEMREMAP_WB or MEMREMAP_WT + * + * memremap() is "ioremap" for cases where it is known that the resource + * being mapped does not have i/o side effects and the __iomem + * annotation is not applicable. + * + * MEMREMAP_WB - matches the default mapping for "System RAM" on + * the architecture. This is usually a read-allocate write-back cache. + * Morever, if MEMREMAP_WB is specified and the requested remap region is RAM + * memremap() will bypass establishing a new mapping and instead return + * a pointer into the direct map. + * + * MEMREMAP_WT - establish a mapping whereby writes either bypass the + * cache or are written through to memory and never exist in a + * cache-dirty state with respect to program visibility. Attempts to + * map "System RAM" with this mapping type will fail. + */ +void *memremap(resource_size_t offset, size_t size, unsigned long flags) +{ + int is_ram = region_intersects(offset, size, "System RAM"); + void *addr = NULL; + + if (is_ram == REGION_MIXED) { + WARN_ONCE(1, "memremap attempted on mixed range %pa size: %#lx\n", + &offset, (unsigned long) size); + return NULL; + } + + /* Try all mapping types requested until one returns non-NULL */ + if (flags & MEMREMAP_WB) { + flags &= ~MEMREMAP_WB; + /* + * MEMREMAP_WB is special in that it can be satisifed + * from the direct map. Some archs depend on the + * capability of memremap() to autodetect cases where + * the requested range is potentially in "System RAM" + */ + if (is_ram == REGION_INTERSECTS) + addr = __va(offset); + else + addr = ioremap_cache(offset, size); + } + + /* + * If we don't have a mapping yet and more request flags are + * pending then we will be attempting to establish a new virtual + * address mapping. Enforce that this mapping is not aliasing + * "System RAM" + */ + if (!addr && is_ram == REGION_INTERSECTS && flags) { + WARN_ONCE(1, "memremap attempted on ram %pa size: %#lx\n", + &offset, (unsigned long) size); + return NULL; + } + + if (!addr && (flags & MEMREMAP_WT)) { + flags &= ~MEMREMAP_WT; + addr = ioremap_wt(offset, size); + } + + return addr; +} +EXPORT_SYMBOL(memremap); + +void memunmap(void *addr) +{ + if (is_vmalloc_addr(addr)) + iounmap((void __iomem *) addr); +} +EXPORT_SYMBOL(memunmap); -- cgit