On Thu, Apr 23, 2015 at 2:30 PM, Bjorn Helgaas bhelgaas@google.com wrote:
Your i915 does not have a ROM BAR in hardware. If the default video device has no ROM BAR, pci_fixup_video() sets IORESOURCE_ROM_SHADOW even though the resource flags are zero because the BAR itself doesn't exist.
If IORESOURCE_ROM_SHADOW is set, pci_map_rom() assumes there's a shadow ROM image at 0xC0000. Is there a shadow image even if the device itself doesn't have a ROM BAR?
On UEFI systems, there's no special reason to believe that there's anything at 0xc0000 - it depends on whether a CSM got loaded or not. Everything is awful. So...
int pcibios_add_device(struct pci_dev *dev) { if (dev-is-default-vga-device) { dev->rom = 0xC0000; dev->romlen = 0x20000; }
I don't know what we want to do here. This is, at some level, fundamentally wrong - however, it also wouldn't surprise me if this is also the only copy of the video ROM we have on some UEFI systems, especially since I believe that Windows 7 still required that there be a legacy ROM it could use for bootloader modesetting on UEFI platforms. So simply making this conditional on BIOS may break existing machines. But if there *is* a ROM there then we should be able to id it from the usual video ROM signature?