From: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Date: Wed, 11 Aug 2010 01:02:45 +0000 (-0700)
Subject: fbmem: VM_IO set, but not propagated
X-Git-Tag: v2.6.36-rc1~164
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c07fbfd17e614a76b194f371c5331e21e6cffb54;p=pandora-kernel.git

fbmem: VM_IO set, but not propagated

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>
---

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