Re: [PATCH] Remove warning in efi_enter_virtual_mode

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     UEFI stands for "Unified Extensible Firmware Interface", where "Firmware"
     is an ancient African word meaning "Why do something right when you can
     do it so wrong that children will weep and brave adults will cower before
     you", and "UEI" is Celtic for "We missed DOS so we burned it into your
     ROMs". The UEFI specification provides for runtime services (ie, another
     way for the operating system to be forced to depend on the firmware) and
     we rely on these for certain trivial tasks such as setting up the
     bootloader. But some hardware fails to work if we attempt to use these
     runtime services from physical mode, and so we have to switch into virtual
     mode. So far so dreadful.


"UEI" is Celtic for "We missed DOS so we burned it into your ROMS"

I love it "maith an fear"

There are currently only two situations where we need to map EFI Boot
Service regions,

   1. To workaround the firmware bug described in 916f676f8
   2. To access the ACPI BGRT image

but since we haven't seen an i386 implementation that requires either,
this simple fix should suffice for now. Item 2. above does still work on
i386 provided that the BGRT image is not in highmem.

Matt, Peter, Josh, Darren.

Given it's not possible to guarantee someone won't stuff a BGRT into EFI_BOOT_MEMORY >= highmem eventually (and indeed the axioms of the universe pretty much guarantee eventually it will be so) - I'd suggest version 2.

A kernel parameter - rather than a probe for BGRT - since we anticipate BIOS bugs on the way.

Version 2 of the submitted path introduces an early kernel parameter "virt_mapboot" - which is true by default (maintaining the current behavior of mapping EFI_BOOT_MEMORY by default) - but which can be set to false - if your IA32 BIOS is not buggy.

Perhaps it would be better to be optimistic.

Change the behavior of efi_enter_virtual_mode() to do the right thing re: the standard and require passing of a parameter to switch on work-arounds for non-standards conformant BIOS. Note: this approach would break BGRT code - requiring addition of kernel parameters to existing systems - which from a user-friendliness POV is probably verboten....

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