On Wed, Aug 23, 2017 at 03:36:37PM +0200, Laszlo Ersek wrote: > On 08/23/17 15:17, Ard Biesheuvel wrote: > >>>> (My R-b stands; these are comments for a possible followup patch.) > >>>> > >>>> Please see: > >>>> > >>>> - commit 84a75f70e903 ("OvmfPkg/QemuVideoDxe: enable ARM builds", > >>>> 2015-02-23), > >>>> > >>>> - commit 05a537945872 ("OvmfPkg/QemuVideoDxe: Helper functions for > >>>> unaligned port I/O.", 2017-04-07)? > >>>> > >>>> In my opinion, we should now revert parts of these commits, in one > >>>> followup patch: > >>>> > >>>> - from the first commit, we should revert only the "VALID_ARCHITECTURES" > >>>> comment change (the rest is built upon by the second commit, and should > >>>> be preserved) > >>>> > >>>> - from the second commit, we should revert the addition of [Sources.ARM, > >>>> Sources.AARCH64]. > >>>> > >>>> This boils down to removing ARM and AARCH64 references from the > >>>> QemuVideoDxe.inf file. If you agree, could you please submit such a > >>>> followup patch? > >>> > >>> Sure, but pending the graphical GRUB discussion. > >> > >> So, after looking at the GRUB code, I am leaning towards agreeing that > >> this is actually not a problem at all ... probably. The efi_gop driver > >> does a Blt() of the entire screen from an off-screen buffer for all > >> updates _unless_ it fails to allocate that off-screen buffer. > >> > >> So, basically, if you run out of memory at that point, it will try to > >> preserve a way to get messages out about that. I will send a question > >> out to grub-devel regarding this behaviour. > >> > >> However, looking at the specification, a question remains over how > >> software can determine whether direct FB access is possible. I mean, a > >> value of 0 seems like a decent hint, but the spec says nothing on the > >> topic. > >> > > > > It will assume the FB is accessible unless the pixel format is PixelBltOnly > > > > Correct, the UEFI spec (v2.7) says in "12.9 Graphics Output Protocol": > > PixelBltOnly This mode does not support a physical frame buffer. > > and > > PixelFormat Enumeration that defines the physical format of the > pixel. A value of PixelBltOnly implies that a linear > frame buffer is not available for this mode.
-ETOOMANYLEVELSOFINDIRECTION Right, so that's a non-issue. Hopefully, that means other operating systems can also deal with the lack. > IIRC simply recognizing and accepting this enum constant was the point > of Alex's patch. Ah, yes, that makes sense now. It's a bit surprising things work without this patch, but GRUBs fallback seems to match anyway. / Leif _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel