EFI memory allocation

[Simon Glass]

Hi Ilias,

On Mon, 4 Dec 2023 at 05:05, Ilias Apalodimas
<ilias.apalodimas at linaro.org> wrote:
>
> Hi Simon
>
> On Sun, 3 Dec 2023 at 19:44, Simon Glass <sjg at chromium.org> wrote:
> >
> > Hi Heinrich, Ilias,
> >
> > I had a bit of a look at how memory is allocated in EFI.
> >
> > I see that efi_memory_init() is called quite early in U-Boot. It
> > sometimes allocates memory for a bounce buffer, placing it somewhere
> > in memory. How do we know that that memory is free and not being used
> > by U-Boot?
> >
> > To answer my own question, it excludes U-Boot's malloc() region from
> > the map, so that it cannot overwrite that.
> >
> > But then, what if we use lmb and start loading images into memory.
> > Won't that conflict with EFI?
>
> Yes, Heinrich tried to fix parts of this with commit 06d514d77c37 and

OK, that looks very odd to me.

> we have a 'todo' in the efi subsystem for a few years now [0]
> Michal (+cc'ed) has also pinged me for similar issues in the past.
>
> >
> > I also see that efi_allocate_pages() is called to allocate memory in
> > the EFI code. But this just grabs memory from 'anywhere'...it doesn't
> > respect the U-Boot malloc region.
> >
> > It seems to me that most of the memory allocation in EFI should be
> > done using malloc(). Of course the boot services need to
> > efi_allocate_pages(), etc., but I am not sure that the internal tables
> > should be skipping malloc()?
> >
> > What do you think?
>
> I think that LMB, EFI and the whole memory reservations is a bit of a
> mess. Tom and I discussed this a bit in the past but I'll start
> working on it.
> It needs fixing, but without looking at the code first, I can't
> provide any useful feedback
>
> [0] https://source.denx.de/u-boot/custodians/u-boot-efi/-/issues/2

OK I mad a comment there. We should figure out a design before going ahead.

Regards,
Simon