linux-kernel - Re: EFI boot crash regression (was: Re: 5.6-### doesn't boot)

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Message-ID: <CAKv+Gu9C2gR629xegjVfVkrPhAuG5brONzbL9iDgPSPW0Ffbbw@mail.gmail.com>
Date:   Sat, 1 Feb 2020 17:02:19 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Jörg Otte <jrg.otte@...il.com>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: EFI boot crash regression (was: Re: 5.6-### doesn't boot)

On Sat, 1 Feb 2020 at 16:35, Jörg Otte <jrg.otte@...il.com> wrote:
>
> Am Fr., 31. Jan. 2020 um 19:48 Uhr schrieb Dan Williams
> <dan.j.williams@...el.com>:
> >
> > On Fri, Jan 31, 2020 at 10:37 AM Ingo Molnar <mingo@...nel.org> wrote:
> > >
> > >
> > > (Cc:ed Dan and Ard)
> > >
> > > * Jörg Otte <jrg.otte@...il.com> wrote:
> > >
> > > > Am Fr., 31. Jan. 2020 um 07:43 Uhr schrieb Ingo Molnar <mingo@...nel.org>:
> > > > >
> > > > >
> > > > > * Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> > > > >
> > > > > > On Thu, Jan 30, 2020 at 9:32 AM Jörg Otte <jrg.otte@...il.com> wrote:
> > > > > > >
> > > > > > > my notebook doesn't boot with current kernel. Booting stops right after
> > > > > > > displaying "loading initial ramdisk..". No further displays.
> > > > > > > Also nothing is wriiten to the logs.
> > > > > > >
> > > > > > > last known good kernel is : vmlinuz-5.5.0-00849-gb0be0eff1a5a
> > > > > > > first known bad kernel is : vmlinuz-5.5.0-01154-gc677124e631d
> > > > > >
> > > > > > It would be lovely if you can bisect a bit. But my merges in that
> > > > > > range are all from Ingo:
> > > > > >
> > > > > > Ingo Molnar (7):
> > > > > >     header cleanup
> > > > > >     objtool updates
> > > > > >     RCU updates
> > > > > >     EFI updates
> > > > > >     locking updates
> > > > > >     perf updates
> > > > > >     scheduler updates
> > > > >
> > > > > If I had to guess then perhaps the EFI changes look the most dangerous
> > > > > ones from these trees - but in principle most of these trees could
> > > > > contain a boot crasher/hang bug.
> > > > >
> > > > > > but not having any messages at all makes it hard to guess where it
> > > > > > would be.
> > > > >
> > > > > To improve debug output:
> > > > >
> > > > > Removing any 'fbcon' options in /boot/grub/grub.cfg and adding this to
> > > > > the boot options might improve the debug output:
> > > > >
> > > > >   earlyprintk=vga initcall_debug ignore_loglevel debug panic_on_warn
> > > > >
> > > > > So for example if the relevant kernel boot entry in grub.cfg looks like
> > > > > this:
> > > > >
> > > > >   linux   /vmlinuz-5.3.0-26-generic root=UUID=1bcxabe3-0b62-4x04-b456-47cd90c0e6x4 ro  splash $vt_handoff
> > > > >
> > > > > Then editing it to the following could in principle produce (much) more
> > > > > verbose boot output:
> > > > >
> > > > >   linux   /vmlinuz-5.3.0-26-generic root=UUID=1bcxabe3-0b62-4x04-b456-47cd90c0e6x4 ro earlyprintk=vga initcall_debug ignore_loglevel debug panic_on_warn $vt_handoff
> > > > >
> > > > > If this produces more output than just "loading initial ramdisk..' then a
> > > > > photo of the hung screen would be sufficient, no need to transcribe it.
> > > > >
> > > > > > A few bisect runs would narrow it down a fair amount. Bisecting all the
> > > > > > way would be even better, of course,
> > > > >
> > > > > Agreed!
> > > > >
> > > > > If compiling full kernels for bisections takes too long (for example
> > > > > because the .config is from a distro kernel) then running "make
> > > > > localmodconfig" to create a config tailored to the currently active
> > > > > modules will cut down significantly on build time.
> > > > >
> > > > > Also, a warning: if the normal boot log contains spurious warnings then
> > > > > the new 'panic_on_warn' option will cause additional trouble on good
> > > > > kernels.
> > > >
> > > > It's bisected.
> > > > The first bad commit is :
> > > > 1db91035d01aa8bfa2350c00ccb63d629b4041ad
> > > > efi: Add tracking for dynamically allocated memmaps
> > >
> > > Thanks a ton, that's very useful!
> > >
> > > I've Cc:-ed the EFI gents who are developing this code, maybe they'll
> > > spot the bug.
> >
> > I'll take a look. Jörg, can you paste a full dmesg from a good boot?
>
> Here it is.
>

Hello Jörg,

Could you please try whether the change below fixes the issue?

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 59f7f6d60cf6..ae923ee8e2b4 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -308,7 +308,7 @@ static void __init efi_clean_memmap(void)
                        .phys_map = efi.memmap.phys_map,
                        .desc_version = efi.memmap.desc_version,
                        .desc_size = efi.memmap.desc_size,
-                       .size = data.desc_size * (efi.memmap.nr_map -
n_removal),
+                       .size = efi.memmap.desc_size *
(efi.memmap.nr_map - n_removal),
                        .flags = 0,
                };