kernel panic on host power on about u-boot

[shenki]

I suspect this is due to my removal of the VGA setup from u-boot:

6d9e287#diff-84ea64abf02622ef709560b072e47382L83

I deleted this as u-boot wasn't using VGA. Oops.

I will test this tory by doing the equivalent setup in the kernel.

Seperaretly, we should fix the host so it does not crash when the BMC has done something it does not expect.

Finally, as we discussed on Thursday, we should work out a way for the BMC to communicate to the host kernel that the VGA device is not present and should not be touched. @jk-ozlabs suggested removing the device tree node for the vga device before the kenrel sees it.

[mdmillerii]

The vga node is discovered over the PCIe bus and not via the host device tree. (there are security bits that can disable the vga device from the host).

I believe the issue here is the BMC crashes when the host boots, around the time the VGA driver is initializing.

The driver uses some scratch registers to find out how much BMC ram to use for the vga device. I suspect this memory was not reserved from the BMC and the host stomped on the BMC kernel's memory.

[shenki]

I mistakenly thought the null pointer dereference was on the host.

You're correct @mdmillerii, we don't reserve any memory for the vga device in OpenBMC