Re: strange grub error on ARM64

[Atish Patra]

On Mon, Mar 6, 2023 at 1:25 PM Fabian Vogt <fvogt@suse.de> wrote:
>
> Hi,
>
> Am Montag, 6. März 2023, 21:59:23 CET schrieb Daniel Kiper:
> > Adding Gary and Michael...
> >
> > Gary, Michael, could you help with this? Or at least forward this email
> > to folks who may help...
> >
> > Daniel
> >
> > On Mon, Mar 06, 2023 at 10:56:52AM -0800, Atish Patra wrote:
> > > Hi,
> > > I am working on a cross-architecture cleanup series that removes the
> > > arch specific headers from RISC-V, ARM, ARM64 and unifies the linux
> > > loader on ARM64 & Linux.
> > >
> > > The v7 version can be found here.
> > > https://lists.gnu.org/archive/html/grub-devel/2023-02/msg00046.html
> > >
> > > It had a few bugs which are fixed and can be found here.
> > >
> > > Here are the patches
> > > https://github.com/atishp04/grub/commits/riscv_uefi_v8
> > >
> > > Anybody with ARM64 and/or test setup: Can you please do a quick test
> > > to see if you see similar or any other failure ?
> > >
> > > I noticed a very strange error during ARM64 testing. I have probably
> > > done something stupid during the grub build
> > > as I can reproduce this with upstream grub as well.
> > >
> > > I was trying to boot an OpenSuse image in qemu virt machine for ARM64 as 
> > > per
> > > the instructions[1]. The stock grub image works fine however my custom
> > > build fails to boot
> > > and drops to the grub command line. It seems the grub detects the disk
> > > but doesn't read the root partition correctly on my cross-compiled image.
> > > It has one additional directory ("@") which I don't see when I mount
> > > the disk. it doesn't list any files as well.
>
> What you see is the expected behaviour with upstream GRUB.
> The btrfs volume contains various subvolumes below @ which are mounted into 
> the
> root file system at various points. The root filesystem itself is at
> @/.snapshots/<number>/snapshot/ and set as the default subvolume. That's what
> is mounted in a running system if you pass default flags. To see the same as
> GRUB, you can do mount -o subvolume=/ /dev/foo3 /mnt.
>

Thanks!! Thank god I am not crazy as I thought I was ;)

> Downstream there's a patch (and multiple related ones) that makes GRUB mount
> the default subvolume instead of the root of the filesystem:
> https://build.opensuse.org/package/view_file/openSUSE:Factory/grub2/grub2-btrfs-03-follow_default.patch?expand=1&rev=285
>

Is this the only patch or I need to pull all the patches on that tree
to make it work ?

Is there an easy way to test upstream grub stuff on ARM64 in case I
need to pull more dependent patches to make it work?

> The design of the "Boot into Snapshot" functionality relies on this.
>
> > > ============= Cross compiled grub image =====================
> > > grub> ls -l (hd0,gpt3)/
> > > DIR          20230302080325 @/
> > >
> > > grub> ls -l (hd0,gpt3)/@/
> > > DIR          20230302080326 boot/
> > > DIR         srv/
> > > DIR          20230302080326 usr/
> > > DIR         opt/
> > > DIR          20230302080326 home/
> > > DIR         var/
> > > DIR         tmp/
> > > DIR         root/
> > >
> > > grub> ls -l (hd0,gpt3)/@/boot/
> > > DIR          20230302080326 grub2/
> > >
> > > grub>
> > > ============= Stock grub image from the OpenSuse 
> > > image=====================
> > > grub> ls (hd0,gpt3)/
> > > dev/ run/ boot/ config.partids lib sbin srv/ usr/ opt/ config.bootoptions 
> > > lib64
> > > .snapshots/ bin home/ etc/ var/ tmp/ sys/ mnt/ proc/ root/
> > >
> > > The same build steps works fine for RISC-V for OpenSuse image though.
> > > However, I couldn't figure out what it was. Any help is appreciated.
>
> It's possible that it does not use snapshot or not even btrfs.
>
> Cheers,
> Fabian
>
> > > [1] https://en.opensuse.org/openSUSE:AArch64
> > >
> > > --
> > > Regards,
> > > Atish
> >
> > _______________________________________________
> > Grub-devel mailing list
> > Grub-devel@gnu.org
> > https://lists.gnu.org/mailman/listinfo/grub-devel
>
>


-- 
Regards,
Atish