Received-SPF: pass (google.com: domain of linux-kernel+bounces-89922-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Precedence: bulk
MIME-Version: 1.0
References: <20240227151907.387873-11-ardb+git@google.com> <20240227151907.387873-13-ardb+git@google.com>
 <20240228205540.GIZd-dzFYIBbtfIAo3@fat_crate.local> <CAMj1kXGhZU+FE2gE262Q8_vZEFHicsRtVPzXT-dhhCvBuiMjUA@mail.gmail.com>
 <20240301160921.GBZeH9sZhp73xX40ze@fat_crate.local> <CAMj1kXFJwEUExy7+Snh3QHVn-ATj0C+sYje22Qmc+y=cCtAV7g@mail.gmail.com>
 <20240301173323.GDZeIRY_BVBqpudkEo@fat_crate.local> <20240303192654.GAZeTO_nxJ4bE2A2zD@fat_crate.local>
In-Reply-To: <20240303192654.GAZeTO_nxJ4bE2A2zD@fat_crate.local>
From: Ard Biesheuvel <ardb@kernel.org>
Date: Sun, 3 Mar 2024 22:56:49 +0100
Message-ID: <CAMj1kXEmNWNH8ZRXcMQ=NKyvOWd4=K5kC4mZMzH-8BmBtvmw+A@mail.gmail.com>
Subject: Re: [PATCH v7 2/9] x86/startup_64: Defer assignment of 5-level paging
 global variables
To: Borislav Petkov <bp@alien8.de>
Cc: Ard Biesheuvel <ardb+git@google.com>, linux-kernel@vger.kernel.org, 
	Kevin Loughlin <kevinloughlin@google.com>, Tom Lendacky <thomas.lendacky@amd.com>, 
	Dionna Glaze <dionnaglaze@google.com>, Thomas Gleixner <tglx@linutronix.de>, 
	Ingo Molnar <mingo@redhat.com>, Dave Hansen <dave.hansen@linux.intel.com>, 
	Andy Lutomirski <luto@kernel.org>, Brian Gerst <brgerst@gmail.com>
Content-Type: text/plain; charset="UTF-8"

On Sun, 3 Mar 2024 at 20:27, Borislav Petkov <bp@alien8.de> wrote:
>
..
>
> Btw, on a semi-related note, do you have an idea whether a normal guest
> kernel using OVMF istead of seabios would be even able to boot a kernel
> supplied with -kernel like above but without an -initrd?
>

How are you passing the root device to the kernel? Via root= on the
command line?

> I have everything builtin and the same kernel boots fine in a guest with
> a
> [    0.000000] SMBIOS 3.0.0 present.
> [    0.000000] DMI: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
>

OK, so this is SeaBIOS

> but if I try to boot the respective guest installed with the OVMF BIOS
> from the debian package:
>
> [    0.000000] efi: EFI v2.7 by Debian distribution of EDK II
> [    0.000000] efi: SMBIOS=0x7f788000 SMBIOS 3.0=0x7f786000 ACPI=0x7f97e000 ACPI 2.0=0x7f97e014 MEMATTR=0x7ddfe018
>

and this is OVMF.

I have tried both of these, with i440fx as well as q35, and they all
work happily with my Debian guest image passed via -hda to QEMU, and
with root=/dev/sda2 on the kernel command line.


> it fails looking up the /dev/root device major/minor deep in the bowels
> of the vfs:
>
> [    2.565651] do_new_mount:
> [    2.566380] vfs_get_tree: fc->root: 0000000000000000
> [    2.567298] kern_path: filename: ffff88800d666000 of name: /dev/root
> [    2.568418] kern_path: ret: 0
> [    2.569009] lookup_bdev: kern_path(/dev/root, , path: ffff88800e537380), error: 0
> [    2.571645] lookup_bdev: inode->i_rdev: 0x0
> [    2.572417] get_tree_bdev: lookup_bdev(/dev/root, dev: 0x0), error: 0
>                                                      ^^^^^^^^^
>
> That dev_t should be 0x800002 - the major and minor of /dev/sda2 but it
> looks like something else is missing in this case...
>

How did you get this output? Are these debug printk()s you added yourself?