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Message-Id: <20201103095859.228149242@linutronix.de>
Date: Tue, 03 Nov 2020 10:27:38 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Linus Torvalds <torvalds@...uxfoundation.org>,
Peter Zijlstra <peterz@...radead.org>,
Paul McKenney <paulmck@...nel.org>,
Christoph Hellwig <hch@....de>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
Alexander Viro <viro@...iv.linux.org.uk>,
Benjamin LaHaise <bcrl@...ck.org>,
linux-fsdevel@...r.kernel.org, linux-aio@...ck.org,
Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
x86@...nel.org, Vineet Gupta <vgupta@...opsys.com>,
linux-snps-arc@...ts.infradead.org,
Russell King <linux@...linux.org.uk>,
Arnd Bergmann <arnd@...db.de>,
linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org,
Michal Simek <monstr@...str.eu>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
linux-mips@...r.kernel.org, Nick Hu <nickhu@...estech.com>,
Greentime Hu <green.hu@...il.com>,
Vincent Chen <deanbo422@...il.com>,
Michael Ellerman <mpe@...erman.id.au>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
linuxppc-dev@...ts.ozlabs.org,
"David S. Miller" <davem@...emloft.net>,
sparclinux@...r.kernel.org, Chris Zankel <chris@...kel.net>,
Max Filippov <jcmvbkbc@...il.com>,
linux-xtensa@...ux-xtensa.org, Ingo Molnar <mingo@...nel.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
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Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Christian Koenig <christian.koenig@....com>,
Huang Rui <ray.huang@....com>, David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
dri-devel@...ts.freedesktop.org,
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Gerd Hoffmann <kraxel@...hat.com>,
virtualization@...ts.linux-foundation.org,
spice-devel@...ts.freedesktop.org, Ben Skeggs <bskeggs@...hat.com>,
nouveau@...ts.freedesktop.org,
Jani Nikula <jani.nikula@...ux.intel.com>,
Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
intel-gfx@...ts.freedesktop.org
Subject: [patch V3 26/37] io-mapping: Provide iomap_local variant
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@...utronix.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,
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