[U-Boot] [PATCH 1/1] efi_loader: remove efi_exit_caches()

[Peter Robinson]

On Mon, Jul 22, 2019 at 2:36 PM Tom Rini <trini at konsulko.com> wrote:
>
> On Sun, Jul 21, 2019 at 10:46:24AM +0100, Peter Robinson wrote:
> > > >>> On Fri, Jul 19, 2019 at 7:28 PM Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
> > > >>>>
> > > >>>> In GRUB before 2.04 a bug existed which did not allow booting some ARM32
> > > >>>> boards if U-Boot did not disable caches, cf.
> > > >>>> https://lists.linaro.org/pipermail/cross-distro/2019-July/000933.html
> > > >>>>
> > > >>>> In ExitBootServices() we were disabling the caches by calling
> > > >>>> cleanup_before_linux(). This workaround is not needed anymore.
> > > >>>
> > > >>> Do we want to remove this straight away? A lot of distributions will
> > > >>> take time to move to grub 2.04 because it's been a long time between
> > > >>> grub releases so they'll have quite a patch delta to re-align to the
> > > >>> new release. Fedora for example will rebase to grub 2.04 in Fedora 32
> > > >>> which will start development end of August but won't be released until
> > > >>> next year.
> > > >>
> > > >> As described below this code does not remove any functionality that was
> > > >> active in U-Boot v2019.04 or v2019.07.
> > > >>
> > > >> I can see nothing in https://fedoraproject.org/wiki/Updates_Policy
> > > >> stopping GRUB 2.04 from being made available for stable Fedora releases.
> > > >
> > > > The maintainers believe that it's too intrusive to land now and they
> > > > want maximum testing time before it gets to stable users, funnily
> > > > enough people don't like it when their machines cease to boot.
> > >
> > > Why should anybody's machines cease to boot?
> > >
> > > If Fedora does not role out a new U-Boot they are fine. If Fedora roles
> > > out a new U-Boot they should role out a matching GRUB and they are fine too.
> > >
> > > The venturous who build their own U-Boot should know how to role back
> > > their system if needed.
> >
> > You've clearly never maintained a distribution across 1000s of device
> > types and 100s of thousands of users.
> >
> > We will be shipping Fedora 31 with U-Boot 2019.10 and the current
> > version of grub that the maintainers wish to support, if that requires
> > me to revert a number of your changes I will, which will be an
> > inconvenience and probably take more time than I have spare but I will
> > survive. I find it strange you fix one OS only to break another. How
> > will this work for users that want to boot a newly released device
> > which has recently added U-Boot support to an already released stable
> > OS?
> >
> > If you wish to actively break currently working use cases that's your
> > prerogative that is your choice but I find breaking currently working
> > use cases without a reasonable window to migrate dependencies actively
> > hostile which has tended to not be the way U-Boot has worked in the
> > past for such things as DM, so breaking a interface to the way OSes
> > boot IMO is even worse.
>
> OK, we have a problem here.  A better example than DM would be the
> various work-arounds we have (or carried for ages) to allow using newer
> U-Boot with various old and broken kernels.  So no, we need to keep this
> work-around for a long while.  What's the EOL date for any Linux
> distribution that uses this broken grub?  The first U-Boot release post
> that EOL date is when we can drop this particular bit of work-around
> code.

Well Fedora 31 would be EOL around Nov/Dec 2020, and while I know the
CentOS team uses the Fedora U-Boot but I believe they boot their
arm-32 instances with extlinux to date. I can't speak for any of the
other distros in this regard.

Peter