[PATCH v2 3/3] lmb: consider EFI memory map

[Simon Glass]

Hi Mark,

On Wed, 11 Jan 2023 at 15:59, Mark Kettenis <mark.kettenis at xs4all.nl> wrote:
>
> > From: Simon Glass <sjg at chromium.org>
> > Date: Wed, 11 Jan 2023 14:08:27 -0700
>
> Hi Simon,
>
> > Hi Heinrich,
> >
> > On Wed, 11 Jan 2023 at 11:03, Heinrich Schuchardt
> > <heinrich.schuchardt at canonical.com> wrote:
> > >
> > >
> > >
> > > On 1/11/23 18:55, Simon Glass wrote:
> > > > Hi Heinrich,
> > > >
> > > > On Wed, 11 Jan 2023 at 09:59, Heinrich Schuchardt
> > > > <heinrich.schuchardt at canonical.com> wrote:
> > > >>
> > > >>
> > > >>
> > > >> On 1/11/23 17:48, Simon Glass wrote:
> > > >>> Hi,
> > > >>>
> > > >>> On Wed, 11 Jan 2023 at 06:59, Tom Rini <trini at konsulko.com> wrote:
> > > >>>>
> > > >>>> On Wed, Jan 11, 2023 at 08:43:37AM +0100, Heinrich Schuchardt wrote:
> > > >>>>>
> > > >>>>>
> > > >>>>> On 1/11/23 01:15, Simon Glass wrote:
> > > >>>>>> Hi Heinrich,
> > > >>>>>>
> > > >>>>>> On Mon, 9 Jan 2023 at 13:53, Heinrich Schuchardt
> > > >>>>>> <heinrich.schuchardt at canonical.com> wrote:
> > > >>>>>>>
> > > >>>>>>>
> > > >>>>>>>
> > > >>>>>>> On 1/9/23 21:31, Simon Glass wrote:
> > > >>>>>>>> Hi Mark,
> > > >>>>>>>>
> > > >>>>>>>> On Mon, 9 Jan 2023 at 13:20, Mark Kettenis <mark.kettenis at xs4all.nl> wrote:
> > > >>>>>>>>>
> > > >>>>>>>>>> From: Simon Glass <sjg at chromium.org>
> > > >>>>>>>>>> Date: Mon, 9 Jan 2023 13:11:01 -0700
> > > >>>>>>>>>>
> > > >>>>>>>>>> Hi Heinrich,
> > > >>>>>>>>>>
> > > >>>>>>>>>>
> > > >>>>>>>>>> We need to fix how EFI does addresses. It seems to use them as
> > > >>>>>>>>>> pointers but store them as u64 ?
> > > >>>>>>>
> > > >>>>>>> That is similar to what you have been doing with physical addresses.
> > > >>>>>>>
> > > >>>>>>>>>
> > > >>>>>>>>> They're defined to a 64-bit unsigned integer by the UEFI
> > > >>>>>>>>> specification, so you can't change it.
> > > >>>>>>>>
> > > >>>>>>>> I don't mean changing the spec, just changing the internal U-Boot
> > > >>>>>>>> implementation, which is very confusing. This confusion is spreading
> > > >>>>>>>> out, too.
> > > >>>>>>>>
> > > >>>>>>>> Regards,
> > > >>>>>>>> Simon
> > > >>>>>>>
> > > >>>>>>> The real interesting thing is how memory should be managed in U-Boot:
> > > >>>>>>>
> > > >>>>>>> I would prefer to create a shared global memory management on 4KiB page
> > > >>>>>>> level used both for EFI and the rest of U-Boot.
> > > >>>>>>
> > > >>>>>> Sounds good.
> > > >>>>>>
> > > >>>>>>>
> > > >>>>>>> What EFI adds to the requirements is that you need more than free
> > > >>>>>>> (EfiConventionalMemory) and used memory. EFI knows 16 different types of
> > > >>>>>>> memory usage (see enum efi_memory_type).
> > > >>>>>>
> > > >>>>>> That's a shame. How much of this is legacy and how much is useful?
> > > >>>>>>
> > > >>>>>>>
> > > >>>>>>> When loading a file (e.g. with the "load" command) this should lead to a
> > > >>>>>>> memory reservation. You should not be able to load a second file into an
> > > >>>>>>> overlapping memory area without releasing the allocated memory first.
> > > >>>>>>>
> > > >>>>>>> This would replace lmb which currently tries to recalculate available
> > > >>>>>>> memory ab initio again and again.
> > > >>>>>>>
> > > >>>>>>> With managed memory we should be able to get rid of all those constants
> > > >>>>>>> like $loadaddr, $fdt_addr_r, $kernel_addr_r, etc. and instead use a
> > > >>>>>>> register of named loaded files.
> > > >>>>>>
> > > >>>>>> This is where standard boot comes in, since it knows what it has
> > > >>>>>> loaded and has pointers to it.
> > > >>>>>>
> > > >>>>>> I see a future where we don't use these commands when we want to save
> > > >>>>>> space. It can save 300KB from the U-Boot size.
> > > >>>>>>
> > > >>>>>> But this really has to come later, since there is so much churn already!
> > > >>>>>>
> > > >>>>>> For now, please don't add EFI allocation into lmb..that is just odd.
> > > >>>>>
> > > >>>>> It is not odd but necessary. Without it the Odroid C2 does not boot but
> > > >>>>> crashes.
> > > >>>>
> > > >>>> It's not Odroid C2, it's anything that with the bad luck to relocate
> > > >>>> over the unprotected EFI structures.
> > > >>>
> > > >>> So can EFI use the lmb calls to reserve its memory? This patch is backwards.
> > > >>
> > > >> Simon, the EFI code can manage memory, LMB cannot.
> > > >>
> > > >> Every time something in U-Boot invokes LMB it recalculates reservations
> > > >> *ab initio*.
> > > >>
> > > >> You could use lib/efi_loader/efi_memory to replace LMB but not the other
> > > >> way round.
> > > >>
> > > >> We should discard LMB and replace it by proper memory management.
> > > >
> > > > We have malloc() but in general this is not used (so far) except with
> > > > some parts of standard boot, and even there we are maintaining
> > > > compatibility with existing fdt_addr_r vars, etc.
> > >
> > > malloc() currently manages a portion of the memory defined by
> > > CONFIG_SYS_MALLOC_LEN. It cannot manage reserved memory. I don't know if
> > > it can allocate from non-consecutive memory areas.
> >
> > This depends on whether we do what you were talking about above, i.e.
> > get rid of the env vars and allocate things. One way to allocate would
> > be with malloc().
>
> Almost certainly not a good idea.  There are all sorts of constraints
> an things like the address where you load your kernel.  Something
> like: "128M of memory, 2MB aligned not crossing a 1GB boundary".

Yes, indeed.

>
> Now *I* would argue that encoding the specific requirements of an OS
> into U-Boot is the wrong approach to start with and that you're better
> off having U-Boot load an OS-specific 2nd (or 3rd or 4th) stage loader
> that loads the actual OS kernel.  Which is why providing an interface
> like EFI that provides a lot of control over memory allocation is so
> useful.

We can just use VBE and the OS can specify the requirements in the FIT.

https://docs.google.com/document/d/1gC8P7l5TgHHi2iHqHfaSi0gItTZtcU8jdpS_mAiFrvw/edit#heading=h.17wg41voij6q

Regards,
Simon