Re: [PATCH v5 3/8] efi_loader: bootstd: Drop bootmgr for sunxi

[Heinrich Schuchardt <xypron.glpk@gmx.de>]

Am 23. November 2024 03:08:02 MEZ schrieb Andre Przywara <andre.przywara@arm.com>:
>On Fri, 15 Nov 2024 07:21:53 -0700
>Simon Glass <sjg@chromium.org> wrote:
>
>Hi Simon, Tom, Heinrich,
>
>sorry for the delay, I was away.
>
>> On Wed, 13 Nov 2024 at 10:50, Tom Rini <trini@konsulko.com> wrote:
>> >
>> > On Wed, Nov 13, 2024 at 08:09:33AM -0700, Simon Glass wrote:
>> >  
>> > > This causes problems with the boot order, so drop it until we can figure
>> > > out a better way to know when bootmgr should be used.
>> > >
>> > > Link: https://lore.kernel.org/u-boot/20241112171205.4e80548d@donnerap.manchester.arm.com/
>> > >
>> > > Signed-off-by: Simon Glass <sjg@chromium.org>  
>> >
>> > I would really prefer a short summary of the contents of the link in the
>> > commit message. I'm not NAK'ing the patch as-is, but it would be helpful
>> > when revisiting this if there was a short explanation of the problem to
>> > solve here and not just "problems with the boot order". Thanks.  
>> 
>> The summary is that sunxi supports FEL (USB boot) but bootmgr is not
>> aware of it, so boots the OS instead.
>
>So that's not the problem: FEL is working fine, since it's marked as
>global, same as efi_bootmgr, but with a lower order number. The problem
>is that the higher priority non-global methods (scripts) are "ignored".
>
>So this is the list without this patch:
>Order  Seq  Name                Description
>-----  ---  ------------------  ------------------
>    0    0  extlinux            extlinux
> glob    1  fel                 FEL
>    2    2  script              script
> glob    3  efi_mgr             EFI bootmgr flow
>    4    4  efi                 EFI
>    5    5  pxe                 PXE
> glob    6  vbe_simple          vbe-simple
>-----  ---  ------------------  ------------------
>
>The sequence looks roughly alright, only that it's not the actual
>order, since "glob" takes precedence. So the actual order is:
>fel -> efi_mgr -> vbe_simple -> extlinux -> script -> efi -> pxe
>And that puts efi_mgr before extlinux and script, which is not what we
>want, because efi_mgr finds bootaa64.efi *somewhere* (eMMC or SD card or
>USB stick) and uses that, even when there is a tailored boot.scr or
>extlinux.conf on the *boot media* which should be higher priority.
>"fel" being first is fine, since it's *only* triggered if someone
>deliberately uploaded a boot script via USB: in this case they surely
>want to execute exactly that.
>
>So I think the underlying problem is the "glob" tag for efi_mgr PLUS
>the fact that it scans all media for bootaa64.efi files. I think it
>would be fine if efi_mgr would just consider EFI boot order variables,
>and would ignore any "removable media" default files (bootaa64.efi).
>The "efi" bootmeth does the scanning as well, and it's fine there,
>since it's lower priority, so we can still boot EFI systems.
>
>I guess it would make sense if an installer on an USB stick should boot
>even if there is something on the eMMC, for instance. But we want to
>control that, and we can't, because the order is ignored due to the
>"glob" flag.
>
>So while I agree that disabling efi_bootmgr sounds like a hack, it
>solves the problem quite elegantly: We keep the (current) boot order,
>which prioritises scripts over EFI, but still retain EFI. If people
>want EFI first, they can change the order in the environment (I think?).
>
>Without that patch there is quite a regression for users, because
>suddenly any bootaa64.efi files *somewhere* would be booted first, and
>there is no way to turn that off.
>
>This has bitten me actually: for development I put a custom boot.scr on
>an SD card which loads a kernel+DTB via TFTP from my box. And I want
>that to be first, despite there being a proper EFI setup on the eMMC or
>USB drive.
>
>So I hope that clears that up. I am not a big fan of that patch, but I
>would like sunxi to be converted, and Simon seemed to be eager to do
>this as well, so in the interest of not blocking this, I am fine with
>that.

Disabling EFI will break booting for users that rely on it (like me).

>
>Cheers,
>Andre

Yes, the introduction of boot standard changed the boot order and specifically deprioritizing scripts is unexpected.

The priority sequence used to be

scripts
extlinux
efi
pxe

bootmeth_efimgr always running before scripts be fixed. bootmeth_efi should be removed from the code base as redundant.

Best regards

Heinrich