Red Hat Bugzilla – Bug 967265
Grub2 does not ship with iorw module, which prevents booting on certain hardware
Last modified: 2016-12-20 07:38:51 EST
Description of problem:
Certain laptops, especially Apple MacBook pro's ship with a graphics multiplexer due to their dual graphics nature. At this time, this support is still broken in the kernel and will not be fixed soon.
In order to boot these laptops the command "outb" must be available in grub2 so that the gmux can be put into a sane state so the machine will boot.
In order for this to happen, the iorw module should be built by default in grub2. This will not affect any other hardware configurations, but will simplify the currently complex situation for Apple Mac hardware.
It grub2.spec line 538 add:
To the GRUB_MODULES section.
Can you give any references that indicate that this really is the best solution to a real problem?
Even then: This will be of very limited use without a mechanism for using it automatically from grub.cfg.
If you have to generate a custom grub.cfg for this anyway then you can just as well run grub2-install as upstream intended and create a custom .efi .
At this time, when an intel MBP boots, both GPU's are powered on. You can run the high powered gpu, without (much) issue at this point.
Swapping to the intel gpu however, causes the display to go blank. All my attempts to convince kernel developers to actually help, have fallen on deaf ears.
To avoid this, the only solution is to before booting, swap the graphics card to the low powered GPU before boot. To achieve this you must probe memory values to achieve this.
However, you make a good point. I still need to make a custom configuration to grub. Thus I will close this issue.
A howto, for example linked from "common bugs" would probably be helpful for someone ;-)
A fix from the kernel developers should be the only solution. However, they seem to "not care" about this issue ;)
I will write a page on the Fedora wiki later when I have time about this issue.
Re-opening ... since this is still an issue in f23.
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