Re: [SUCCESS] Debugging/fixing a kernel stalled not crashing

[tlaronde%polynum.com@localhost]

Addition (asked by Taylor R Campbell): a current GENERIC boots only
with i915drmkms disabled.

With the framebuffer stuff enabled, it does not boot, and does not even
panic and reboot. It freezes somewhere. The same as the 9.x series.

Le Sat, Aug 20, 2022 at 09:03:52PM +0200, tlaronde%polynum.com@localhost a écrit :
> A final point:
> 
> Context: I rent a baremetal server (OVH) that has an Intel Xeon
> quadcore, IvyBridge, with 16Gb of RAM, 3 2TB disks, an Intel PRO 1000
> ethernet card (but the bandwith is limited to 100Mib). It is an entry
> level offer, that I wanted only for an IPv4 address (there is an IPv6
> address too).
> 
> The images to install include no BSD but only Linux/Debian variants.
> 
> Following instructions from an helpful wiki page, I try to install using
> a Linux rescue disk (provided by OVH), running all in memory, and having
> qemu-system-x86_64 allowing to use a CDROM install image.
> 
> Nothing booted.
> 
> Since it was unclear from the web interface if the boot process was
> depending or not on the information about an image being installed (to
> allow booting from the disk), I then installed a Linux/Debian on only
> one disk (one can select, 1, 2 or 3 disks, but if multiple disks this
> is software RAID).
> 
> Using the rescue system, I then resized the Debian partition and
> installed NetBSD on another partition (dual booting) and, to bypass a
> possible limitation in the booting process (only booting GRUB and
> accessing directly GRUB), I chainloaded the NetBSD stage1 from the GRUB2
> menu, and verified, under qemu, this will boot, using GRUB2 boot once
> feature so that if the NetBSD crashed and reboots, I can go back to
> Debian to try something else.
> 
> Still no success.
> 
> It was almost certain there was a problem with the kernel.
> 
> So I wrote a special /boot.cfg to test various things, custom compiling
> a kernel (since the GENERIC installation one was not running), and tried
> to validate step by step the booting procedure in order to try, after
> to insert a cpu_reboot() instruction in the kernel to see where the
> problem occurred (since when rebooting, I will be able to connect to
> Debian, I would have known that before the instruction, it was OK).
> 
> In order to limit the work, I used once more qemu but to install NetBSD
> on another disk (so that I can in fact use qemu not with the rescue
> system, but directly under Debian without trashing the very disk Debian
> runs from).
> 
> The first test was to see if, indeed, NetBSD stage2 was loaded. The
> menu in /boot.cfg was simple: the instruction "quit".
> 
> => First lesson: this does not work, because the rebooting is not a
> total one, and mapping the drives (in GRUB2) to ensure that the booting
> succeeds, the stage2 reboots but finally back to itself, so the machine 
> was unendlessly rebooting and I had no connection.
> 
> It took me various modifications before realizing it was the case (under
> qemu) so I abandonned the idea and tried to boot a custom kernel,
> without SMP and without framebuffer (i915drmkms).
> 
> This succeeded.
> 
> I then get back to test letting the framebuffer. It didn't work.
> I then disable the framebuffer for everything, and tried with SMP. It
> worked.
> Then, I tried 9.2 GENERIC and 9.3 GENERIC without framebuffer. Both
> work.
> 
> So the final lesson: NetBSD can be installed on such machine but the
> framebuffer is a problem. And NetBSD is not far behind Linux, because
> the Debian distribution is a recent one, and the main clue was in the
> Linux dmesg: 
> 
> Command line: BOOT_IMAGE=/boot/vmlinuz-5.10.0-14-amd64 root=UUID=eea6d0a4-03b6-44e6-8588-ff6c4eba2095 ro nomodeset iommu=pt
> 
> The: nomodeset.
> 
> Linux doesn't work with the embedded graphics (HD 4000) either.
> 
> So it is partly a kernel problem (kernel stalling with framebuffer
> initializations) but mainly an install problem (framebuffer in such
> cases should be disabled).
> 
> If someone thinks there can be interest in how I set dual booting,
> chainloading NetBSD from GRUB2, and configuring the boot procedure, I
> can write a mini-page about it.
> 
> For the rest: problem solved. NetBSD can install on an OVH baremetal
> (at least this kind of machine).
> -- 
>         Thierry Laronde <tlaronde +AT+ polynum +dot+ com>
>                      http://www.kergis.com/
>                     http://kertex.kergis.com/
>                        http://www.sbfa.fr/
> Key fingerprint = 0FF7 E906 FBAF FE95 FD89  250D 52B1 AE95 6006 F40C

-- 
        Thierry Laronde <tlaronde +AT+ polynum +dot+ com>
                     http://www.kergis.com/
                    http://kertex.kergis.com/
                       http://www.sbfa.fr/
Key fingerprint = 0FF7 E906 FBAF FE95 FD89  250D 52B1 AE95 6006 F40C