fbdev/efifb: Honour UEFI memory map attributes when mapping the FB

If the framebuffer address provided by the Graphics Output Protocol
(GOP) is covered by the UEFI memory map, it will tell us which memory
attributes are permitted when mapping this region. In some cases,
(KVM guest on ARM), violating this will result in loss of coherency,
which means that updates sent to the framebuffer by the guest will
not be observeable by the host, and the emulated display simply does
not work.

So if the memory map contains such a description, take the attributes
field into account, and add support for creating WT or WB mappings of
the framebuffer region.

Tested-by: Laszlo Ersek <[email protected]>
Signed-off-by: Ard Biesheuvel <[email protected]>
Acked-by: Bartlomiej Zolnierkiewicz <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Jones <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions