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@oracle.com>
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Tested-by: Eamon Walsh <ewalsh@tycho.nsa.gov>
Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Cc: Dave Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
c07fbfd17e