On Monday, June 25, 2018 11:58:11 AM Ard Biesheuvel wrote:

,On 22 June 2018 at 09:52, Ard Biesheuvel [off-list ref] wrote:

quoted

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.

Cc: linux-fbdev@vger.kernel.org
Cc: Bartlomiej Zolnierkiewicz <redacted>
Cc: Peter Jones <pjones@redhat.com>
Tested-by: Laszlo Ersek <redacted>
Signed-off-by: Ard Biesheuvel <redacted>

Bartlomiej, do you have any comments on this patch? If not, I would
like to queue it in the efi tree.

quoted

@@ -164,6 +168,8 @@ static int efifb_probe(struct platform_device *dev)
        unsigned int size_remap;
        unsigned int size_total;
        char *option = NULL;
+       efi_memory_desc_t md;
+

minor nit: redundant newline

the rest looks fine to me

Acked-by: Bartlomiej Zolnierkiewicz <redacted>

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics