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Subject[099/262] io-mapping: ensure io_mapping_map_atomic _is_ atomic
3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Vetter <daniel.vetter@ffwll.ch>

commit 24dd85ff723f142093f44244764b9b5c152235b8 upstream.

For the !HAVE_ATOMIC_IOMAP case the stub functions did not call
pagefault_disable/_enable. The i915 driver relies on the map
actually being atomic, otherwise it can deadlock with it's own
pagefault handler in the gtt pwrite fastpath.

This is exercised by gem_mmap_gtt from the intel-gpu-toosl gem
testsuite.

v2: Chris Wilson noted the lack of an include.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=38115
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
include/linux/io-mapping.h | 4 ++++
1 file changed, 4 insertions(+)

--- a/include/linux/io-mapping.h
+++ b/include/linux/io-mapping.h
@@ -117,6 +117,8 @@ io_mapping_unmap(void __iomem *vaddr)

#else

+#include <linux/uaccess.h>
+
/* this struct isn't actually defined anywhere */
struct io_mapping;

@@ -138,12 +140,14 @@ static inline void __iomem *
io_mapping_map_atomic_wc(struct io_mapping *mapping,
unsigned long offset)
{
+ pagefault_disable();
return ((char __force __iomem *) mapping) + offset;
}

static inline void
io_mapping_unmap_atomic(void __iomem *vaddr)
{
+ pagefault_enable();
}

/* Non-atomic map/unmap */



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