Bug: kexec on Lenovo ThinkPad T480 disables EFI mode

[Dave Young]

Baoquan, thanks for cc me.

On Sat, 5 Nov 2022 at 11:10, Baoquan He <bhe at redhat.com> wrote:
>
> Add Dave to CC
>
> On 10/28/22 at 01:02pm, ns at tfwno.gf wrote:
> > Greetings,
> >
> > I've been hitting a bug on my Lenovo ThinkPad T480 where kexecing will
> > cause EFI mode (if that's the right term for it) to be unconditionally
> > disabled, even when not using the --noefi option to kexec.
> >
> > What I mean by "EFI mode" being disabled, more than just EFI runtime
> > services, is that basically nothing about the system's EFI is visible
> > post-kexec. Normally you have a message like this in dmesg when the
> > system is booted in EFI mode:
> >
> > [    0.000000] efi: EFI v2.70 by EDK II
> > [    0.000000] efi: SMBIOS=0x7f98a000 ACPI=0x7fb7e000 ACPI 2.0=0x7fb7e014
> > MEMATTR=0x7ec63018
> > (obviously not the real firmware of the machine I'm talking about, but I
> > can also send that if it would be of any help)
> >
> > No such message pops up in my dmesg as a result of this bug, & this
> > causes some fallout like being unable to find the system's DMI
> > information:
> >
> > <6>[    0.000000] DMI not present or invalid.
> >
> > The efivarfs module also fails to load with -ENODEV.
> >
> > I've tried also booting with efi=runtime explicitly but it doesn't
> > change anything. The kernel still does not print the name of the EFI
> > firmware, DMI is still missing, & efivarfs still fails to load.
> >
> > I've been using the kexec_load syscall for all these tests, if it's
> > important.
> >
> > Also, to make it very clear, all this only ever happens post-kexec. When
> > booting straight from UEFI (with the EFI stub), all the aforementioned
> > stuff that fails works perfectly fine (i.e. name of firmware is printed,
> > DMI is properly found, & efivarfs loads & mounts just fine).
> >
> > This is reproducible with a vanilla 6.1-rc2 kernel. I've been trying to
> > bisect it, but it seems like it goes pretty far back. I've got vanilla
> > mainline kernel builds dating back to 5.17 that have the exact same
> > issue. It might be worth noting that during this testing, I made sure
> > the version of the kernel being kexeced & the kernel kexecing were the
> > same version. It may not have been a problem in older kernels, but that
> > would be difficult to test for me (a pretty important driver for this
> > machine was only merged during v5.17-rc4). So it may not have been a
> > regression & just a hidden problem since time immemorial.
> >
> > I am willing to test any patches I may get to further debug or fix
> > this issue, preferably based on the current state of torvalds/linux.git.
> > I can build & test kernels quite a few times per day.
> >
> > I can also send any important materials (kernel config, dmesg, firmware
> > information, so on & so forth) on request. I'll also just mention I'm
> > using kexec-tools 2.0.24 upfront, if it matters.

Can you check the efi runtime in sysfs:
ls /sys/firmware/efi/runtime-map/

If nothing then maybe you did not enable CONFIG_EFI_RUNTIME_MAP=y, it
is needed for kexec UEFI boot on x86_64.

Otherwise you can add debug printf in kexec-tools efi error path to
see what is wrong.
kexec/arch/i386/x86-linux-setup.c : function setup_efi_data

And if it still not work please post your kernel config, I can have a
try although I do not have the t480 now.


> >
> > Regards,
> >
> > _______________________________________________
> > kexec mailing list
> > kexec at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
> >
>