[PATCH v2][EFI] Run EFI in physical mode

Matthew Garrett mjg at redhat.com
Thu Jan 13 12:41:39 EST 2011

On Thu, Jan 13, 2011 at 09:16:26AM -0800, Eric W. Biederman wrote:
> Matthew Garrett <mjg at redhat.com> writes:
> > We're seeing issues with some Dell hardware when EFI is run in physical 
> > mode - it seems that Windows uses virtual mode, so the physical path is 
> > never exercised. I'm not sure that changing the default to physical is 
> > going to be possible without compatibility issues.
> The bootloaders use physical mode, and there shouldn't be a separate
> physical vs virtual mode.  It should be the same code with or without
> relocations applied.  At worst we can set virtual address to the
> physical address, on buggy boards.

Haven't we learned that failing to mimic Windows as closely as possible 
in firmware interactions is a recipe for immense disaster yet? We'll 
never successfully blacklist every broken machine.

> Honestly if the problem is the EFI code is so buggy we can't use it
> in physical mode the answer is almost certainly not to use the
> buggy EFI code.

Which would be fine, except...

> The only bits that I don't think have an alternative are the firmware
> variable accesses.   Which are a nice to have, but not a show stopper
> anywhere.

It's not typically possible to set up the bootloader without EFI 
variable acccess.

Matthew Garrett | mjg59 at srcf.ucam.org

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