Booting with `pci=nobios` fails on Dell XPS 13 9360

Booting with `pci=nobios` fails on Dell XPS 13 9360

[Paul Menzel]

Dear Linux folks,


On the Dell XPS 13 9360/0596KF, BIOS 2.21.0 06/02/2022, booting Linux 
6.9-rc5-00036-g9d1ddab261f3 with `pci=nobios`, the internal keyboard 
does not work, and there are DRHD (IOMMU) errors and intel-lpss errors 
printed by Linux. (As the keyboard does not work, I am unable to enter 
the LUKS passphrase, and capture the Linux messages.)

Is that option supposed to work, and should Linux be able to detect and 
configure itself without the help from the system firmware?


Kind regards,

Paul

Re: Booting with `pci=nobios` fails on Dell XPS 13 9360

[Bjorn Helgaas]

On Wed, Apr 24, 2024 at 07:30:42AM +0200, Paul Menzel wrote:
> On the Dell XPS 13 9360/0596KF, BIOS 2.21.0 06/02/2022, booting Linux
> 6.9-rc5-00036-g9d1ddab261f3 with `pci=nobios`, the internal keyboard does
> not work, and there are DRHD (IOMMU) errors and intel-lpss errors printed by
> Linux. (As the keyboard does not work, I am unable to enter the LUKS
> passphrase, and capture the Linux messages.)
> 
> Is that option supposed to work, and should Linux be able to detect and
> configure itself without the help from the system firmware?

Linux definitely needs help from firmware to boot, but "pci=nobios"
doesn't turn off very much, and I would think Linux would still boot
on a machine like yours that has ACPI with MCFG/ECAM, etc.

My guess is some early PCI config access before we set up ECAM is
failing.  You might be able to capture console output as a video,
especially if you slow it down with boot_delay=.  I've used something
like "nosmp initcall_debug ignore_loglevel boot_delay=60 lpj=3200000"
as a starting point.  Must enable CONFIG_BOOT_PRINTK_DELAY for this to
work.

Bjorn