Re: [PATCH 1/2] UEFI arm64: add noefi boot param

Leif Lindholm
2014-08-06T13:29:53Z

On Wed, Aug 06, 2014 at 02:20:21PM +0100, Matt Fleming wrote:
> > Since this is really turning an x86-specific feature into a generic
> > one, could it be moved to core code?
> > Maybe an efi.mask, reusing the efi_enabled defines, with an
> > efi_disabled macro?
>
> Why the new efi_disabled() and efi.mask? This is all achievable with
> efi_enabled() and efi.flags, in fact, this kind of thing is exactly why
> they were invented.

Because this flag is indicating which facilities we should not try to
enable, rather than which facilities we have enabled.

The EFI_RUNTIME_SERVICES flag is set after successful call to
set_virtual_address_map. The apparent intent of "noefi" is to prevent
that call from being made in the first place.

Anyway, it was just a suggestion - main point was it would make sense
to share the code.

> > Also, since this patch (and its x86 predecessor) is not really
> > "noefi", could this be integrated with the "efi=" patch
> > (http://permalink.gmane.org/gmane.linux.kernel.efi/4405),
> > as an efi=noruntime option?
> >
> > On x86, due to CSM, "noefi" was a useful fallback for completely
> > broken (U)EFI implementations - but on an arm* UEFI system, there will
> > be no fallback. Could it be wrapped in a kernel hacking config option?
>
> I don't mind making "noefi" a synonym for "efi=noruntime" on x86, as
> long as we keep "noefi" around with the same semantics it's always had.

Yeah, that would be nice.

/
Leif