[PATCH v4 4/5] efi: Reserve some memory for initial use

[Simon Glass]

Hi Tom,

On Mon, 14 Oct 2024 at 15:42, Tom Rini <trini at konsulko.com> wrote:
>
> On Mon, Oct 14, 2024 at 02:19:56PM -0600, Simon Glass wrote:
> > Hi,
> >
> > On Fri, 11 Oct 2024 at 23:47, Ilias Apalodimas
> > <ilias.apalodimas at linaro.org> wrote:
> > >
> > > Hi Tom
> > >
> > > On Sat, 12 Oct 2024 at 04:27, Tom Rini <trini at konsulko.com> wrote:
> > > >
> > > > On Sat, Oct 12, 2024 at 12:01:54AM +0200, Heinrich Schuchardt wrote:
> > > > >
> > > > >
> > > > > Am 11. Oktober 2024 23:21:25 MESZ schrieb Simon Glass <sjg at chromium.org>:
> > > > > >The 'point of cooperation' is where U-Boot starts allowing EFI to use
> > > > > >memory outside of the U-Boot region. Until that point, it is desirable
> > > > > >to keep more below U-Boot free for loading images.
> > > > > >
> > > > > >Reserve a small region for this purpose.
> > > > >
> > > > > Your commit message provides no clue why this should be needed.
> >
> > Yes, I hadn't realised that people didn't understand what I was
> > getting at. Tom asked the same question on irc.
> >
> > It allows us to separate the lmb allocations from the EFI allocations,
> > so we don't need to have them both in sync. We use lmb for loading
> > images, then EFI takes over and does what it likes, respecting the
> > existing lmb reservations.
>
> But, again, LMB is not for loading of images. It's for dealing with
> memory reservations of various types.

Up until recently, I believe, my statement was true, but in any case,
this isn't gemaine to the issue here.

The point is, this is a useful distinction, allowing us to avoid the
complexity of keeping them in sync, and avoid putting this pain on
people who are not using EFI. We are either in U-Boot code, in which
case lmb rules, or we are going into an app, in which case EFI rules
(but must read in the lmb info).

We are going to end up with people turning off EFI_LOADER because it
behaves so badly.

Regards,
Simon