The patch titled
fbmem: VM_IO set, but not propagated
has been added to the -mm tree. Its filename is
fbmem-vm_io-set-but-not-propagated.patch
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------------------------------------------------------
Subject: fbmem: VM_IO set, but not propagated
From: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
When we setup up the VMA flags for the mmap flag and we end up using the
fallback mmap functionality we set the vma->vm_flags |= VM_IO. However we
neglect to propagate the flag to the vma->vm_page_prot.
This bug was found when Linux kernel was running under Xen. In that
scenario, any page that has VM_IO flag to it, means that it MUST be a
MMIO/VRAM backend memory , _not_ System RAM. That is what the fbmem.c
does: sets VM_IO, ioremaps the region - everything is peachy.
Well, not exactly. The vm_page_prot does not get the relevant PTE flags
set (_PAGE_IOMAP) which under Xen is a death-kneel to pages that are
referencing real physical devices but don't have that flag set.
This patch fixes this.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Tested-by: Eamon Walsh <ewalsh@xxxxxxxxxxxxx>
Cc: Florian Tobias Schandinat <FlorianSchandinat@xxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/video/fbmem.c | 1 +
1 file changed, 1 insertion(+)
diff -puN drivers/video/fbmem.c~fbmem-vm_io-set-but-not-propagated drivers/video/fbmem.c
--- a/drivers/video/fbmem.c~fbmem-vm_io-set-but-not-propagated
+++ a/drivers/video/fbmem.c
@@ -1362,6 +1362,7 @@ fb_mmap(struct file *file, struct vm_are
vma->vm_pgoff = off >> PAGE_SHIFT;
/* This is an IO map - tell maydump to skip this VMA */
vma->vm_flags |= VM_IO | VM_RESERVED;
+ vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
fb_pgprotect(file, vma, off);
if (io_remap_pfn_range(vma, vma->vm_start, off >> PAGE_SHIFT,
vma->vm_end - vma->vm_start, vma->vm_page_prot))
_
Patches currently in -mm which might be from dgdegra@xxxxxxxxxxxxx are
fbmem-vm_io-set-but-not-propagated.patch
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