From: Thomas Gleixner <tglx@linutronix•de>
To: LKML <linux-kernel@vger•kernel.org>
Cc: Juri Lelli <juri.lelli@redhat•com>,
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Subject: [patch V3 26/37] io-mapping: Provide iomap_local variant
Date: Tue, 03 Nov 2020 10:27:38 +0100 [thread overview]
Message-ID: <20201103095859.228149242@linutronix.de> (raw)
In-Reply-To: 20201103092712.714480842@linutronix.de
Similar to kmap local provide a iomap local variant which only disables
migration, but neither disables pagefaults nor preemption.
Signed-off-by: Thomas Gleixner <tglx@linutronix•de>
---
V3: Restrict migrate disable to the 32bit mapping case and update documentation.
V2: Split out from the large combo patch and add the !IOMAP_ATOMIC variants
---
Documentation/driver-api/io-mapping.rst | 76 +++++++++++++++++++-------------
include/linux/io-mapping.h | 30 +++++++++++-
2 files changed, 74 insertions(+), 32 deletions(-)
--- a/Documentation/driver-api/io-mapping.rst
+++ b/Documentation/driver-api/io-mapping.rst
@@ -20,55 +20,71 @@ as it would consume too much of the kern
mappable, while 'size' indicates how large a mapping region to
enable. Both are in bytes.
-This _wc variant provides a mapping which may only be used
-with the io_mapping_map_atomic_wc or io_mapping_map_wc.
+This _wc variant provides a mapping which may only be used with
+io_mapping_map_atomic_wc(), io_mapping_map_local_wc() or
+io_mapping_map_wc().
+
+With this mapping object, individual pages can be mapped either temporarily
+or long term, depending on the requirements. Of course, temporary maps are
+more efficient. They come in two flavours::
-With this mapping object, individual pages can be mapped either atomically
-or not, depending on the necessary scheduling environment. Of course, atomic
-maps are more efficient::
+ void *io_mapping_map_local_wc(struct io_mapping *mapping,
+ unsigned long offset)
void *io_mapping_map_atomic_wc(struct io_mapping *mapping,
unsigned long offset)
-'offset' is the offset within the defined mapping region.
-Accessing addresses beyond the region specified in the
-creation function yields undefined results. Using an offset
-which is not page aligned yields an undefined result. The
-return value points to a single page in CPU address space.
-
-This _wc variant returns a write-combining map to the
-page and may only be used with mappings created by
-io_mapping_create_wc
+'offset' is the offset within the defined mapping region. Accessing
+addresses beyond the region specified in the creation function yields
+undefined results. Using an offset which is not page aligned yields an
+undefined result. The return value points to a single page in CPU address
+space.
-Note that the task may not sleep while holding this page
-mapped.
+This _wc variant returns a write-combining map to the page and may only be
+used with mappings created by io_mapping_create_wc()
-::
+Temporary mappings are only valid in the context of the caller. The mapping
+is not guaranteed to be globaly visible.
- void io_mapping_unmap_atomic(void *vaddr)
+io_mapping_map_local_wc() has a side effect on X86 32bit as it disables
+migration to make the mapping code work. No caller can rely on this side
+effect.
+
+io_mapping_map_atomic_wc() has the side effect of disabling preemption and
+pagefaults. Don't use in new code. Use io_mapping_map_local_wc() instead.
-'vaddr' must be the value returned by the last
-io_mapping_map_atomic_wc call. This unmaps the specified
-page and allows the task to sleep once again.
+Nested mappings need to be undone in reverse order because the mapping
+code uses a stack for keeping track of them::
-If you need to sleep while holding the lock, you can use the non-atomic
-variant, although they may be significantly slower.
+ addr1 = io_mapping_map_local_wc(map1, offset1);
+ addr2 = io_mapping_map_local_wc(map2, offset2);
+ ...
+ io_mapping_unmap_local(addr2);
+ io_mapping_unmap_local(addr1);
-::
+The mappings are released with::
+
+ void io_mapping_unmap_local(void *vaddr)
+ void io_mapping_unmap_atomic(void *vaddr)
+
+'vaddr' must be the value returned by the last io_mapping_map_local_wc() or
+io_mapping_map_atomic_wc() call. This unmaps the specified mapping and
+undoes the side effects of the mapping functions.
+
+If you need to sleep while holding a mapping, you can use the regular
+variant, although this may be significantly slower::
void *io_mapping_map_wc(struct io_mapping *mapping,
unsigned long offset)
-This works like io_mapping_map_atomic_wc except it allows
-the task to sleep while holding the page mapped.
-
+This works like io_mapping_map_atomic/local_wc() except it has no side
+effects and the pointer is globaly visible.
-::
+The mappings are released with::
void io_mapping_unmap(void *vaddr)
-This works like io_mapping_unmap_atomic, except it is used
-for pages mapped with io_mapping_map_wc.
+Use for pages mapped with io_mapping_map_wc().
At driver close time, the io_mapping object must be freed::
--- a/include/linux/io-mapping.h
+++ b/include/linux/io-mapping.h
@@ -83,6 +83,21 @@ io_mapping_unmap_atomic(void __iomem *va
}
static inline void __iomem *
+io_mapping_map_local_wc(struct io_mapping *mapping, unsigned long offset)
+{
+ resource_size_t phys_addr;
+
+ BUG_ON(offset >= mapping->size);
+ phys_addr = mapping->base + offset;
+ return __iomap_local_pfn_prot(PHYS_PFN(phys_addr), mapping->prot);
+}
+
+static inline void io_mapping_unmap_local(void __iomem *vaddr)
+{
+ kunmap_local_indexed((void __force *)vaddr);
+}
+
+static inline void __iomem *
io_mapping_map_wc(struct io_mapping *mapping,
unsigned long offset,
unsigned long size)
@@ -101,7 +116,7 @@ io_mapping_unmap(void __iomem *vaddr)
iounmap(vaddr);
}
-#else
+#else /* HAVE_ATOMIC_IOMAP */
#include <linux/uaccess.h>
@@ -166,7 +181,18 @@ io_mapping_unmap_atomic(void __iomem *va
preempt_enable();
}
-#endif /* HAVE_ATOMIC_IOMAP */
+static inline void __iomem *
+io_mapping_map_local_wc(struct io_mapping *mapping, unsigned long offset)
+{
+ return io_mapping_map_wc(mapping, offset, PAGE_SIZE);
+}
+
+static inline void io_mapping_unmap_local(void __iomem *vaddr)
+{
+ io_mapping_unmap(vaddr);
+}
+
+#endif /* !HAVE_ATOMIC_IOMAP */
static inline struct io_mapping *
io_mapping_create_wc(resource_size_t base,
next prev parent reply other threads:[~2020-11-03 12:35 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-03 9:27 [patch V3 00/37] mm/highmem: Preemptible variant of kmap_atomic & friends Thomas Gleixner
2020-11-03 9:27 ` [patch V3 01/37] mm/highmem: Un-EXPORT __kmap_atomic_idx() Thomas Gleixner
2020-11-03 9:27 ` [patch V3 02/37] highmem: Remove unused functions Thomas Gleixner
2020-11-03 9:27 ` [patch V3 03/37] fs: Remove asm/kmap_types.h includes Thomas Gleixner
2020-11-03 11:12 ` David Sterba
2020-11-03 9:27 ` [patch V3 04/37] sh/highmem: Remove all traces of unused cruft Thomas Gleixner
2020-11-03 9:27 ` [patch V3 05/37] asm-generic: Provide kmap_size.h Thomas Gleixner
2020-11-03 12:25 ` Arnd Bergmann
2020-11-03 9:27 ` [patch V3 06/37] highmem: Provide generic variant of kmap_atomic* Thomas Gleixner
2020-11-03 9:27 ` [patch V3 07/37] highmem: Make DEBUG_HIGHMEM functional Thomas Gleixner
2020-11-03 9:27 ` [patch V3 08/37] x86/mm/highmem: Use generic kmap atomic implementation Thomas Gleixner
2020-11-03 9:27 ` [patch V3 09/37] arc/mm/highmem: " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 10/37] ARM: highmem: Switch to generic kmap atomic Thomas Gleixner
2020-11-12 8:10 ` Marek Szyprowski
2020-11-12 11:03 ` Thomas Gleixner
2020-11-12 11:07 ` Sebastian Andrzej Siewior
2020-11-03 9:27 ` [patch V3 11/37] csky/mm/highmem: " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 12/37] microblaze/mm/highmem: " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 13/37] mips/mm/highmem: " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 14/37] nds32/mm/highmem: " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 15/37] powerpc/mm/highmem: " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 16/37] sparc/mm/highmem: " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 17/37] xtensa/mm/highmem: " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 18/37] highmem: Get rid of kmap_types.h Thomas Gleixner
2020-11-03 9:27 ` [patch V3 19/37] mm/highmem: Remove the old kmap_atomic cruft Thomas Gleixner
2020-11-03 9:27 ` [patch V3 20/37] io-mapping: Cleanup atomic iomap Thomas Gleixner
2020-11-03 9:27 ` [patch V3 21/37] Documentation/io-mapping: Remove outdated blurb Thomas Gleixner
2020-11-03 9:27 ` [patch V3 22/37] highmem: High implementation details and document API Thomas Gleixner
2020-11-03 17:48 ` Linus Torvalds
2020-11-03 19:00 ` Thomas Gleixner
2020-11-03 9:27 ` [patch V3 23/37] sched: Make migrate_disable/enable() independent of RT Thomas Gleixner
2020-11-03 9:27 ` [patch V3 24/37] sched: highmem: Store local kmaps in task struct Thomas Gleixner
2020-11-03 13:49 ` Thomas Gleixner
2020-11-03 13:51 ` [patch V4 " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 25/37] mm/highmem: Provide kmap_local* Thomas Gleixner
2020-11-03 9:27 ` Thomas Gleixner [this message]
2020-11-03 9:27 ` [patch V3 27/37] x86/crashdump/32: Simplify copy_oldmem_page() Thomas Gleixner
2020-11-03 9:27 ` [patch V3 28/37] mips/crashdump: " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 29/37] ARM: mm: Replace kmap_atomic_pfn() Thomas Gleixner
2020-11-03 9:27 ` [patch V3 30/37] highmem: Remove kmap_atomic_pfn() Thomas Gleixner
2020-11-03 9:27 ` [patch V3 31/37] drm/ttm: Replace kmap_atomic() usage Thomas Gleixner
2020-11-03 9:27 ` [patch V3 32/37] drm/vmgfx: Replace kmap_atomic() Thomas Gleixner
2020-11-03 9:27 ` [patch V3 33/37] highmem: Remove kmap_atomic_prot() Thomas Gleixner
2020-11-03 9:27 ` [patch V3 34/37] drm/qxl: Replace io_mapping_map_atomic_wc() Thomas Gleixner
2020-11-03 9:27 ` [patch V3 35/37] drm/nouveau/device: " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 36/37] drm/i915: " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 37/37] io-mapping: Remove io_mapping_map_atomic_wc() Thomas Gleixner
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