Slow boot on rocky linux 10 latest kernel

acebmxer

This is on fresh install Debian 13 deployed from XO Hub - 6.12.38+deb13-amd64. I do not see this behavior on Ubuntu.

after update 6.12.90+deb13.1-amd64
still happens.

TeddyAstie

@acebmxer I don't observe the same issue on Debian 13 Cloud-Init (both 6.12.38+deb13-amd64 and updated 6.12.90+deb13.1-amd64).

Though it still takes some time to boot (especially at loading the ramdisk) but it's not related to this pv spinlock issue and mostly a "BIOS guest" related issue.
But I'm testing on a Intel machine.

henri9813

Hello,

To gave more details abouit my case:

XCPNG: 8.3.0
CPU: AMD EPYC 4464P 12-Core Processor
Kernel: 6.12.0-211.18.1.el10_2.x86_64

acebmxer

I was going to suggest it might be a amd issue. I can try later on work host that are intel.

MajorP93

@TeddyAstie These spinlock events that cause slow boot also happen on my Debian VMs. Also AMD Epyc CPU in my case.

I noticed that this only happens for UEFI enabled VMs. VMs booting in BIOS mode do not have this issue.

TeddyAstie

@MajorP93 can you give the kernel version of all the affected vs non-affected guests ?

olivierlambert

I can reproduce on Debian 13 with stock kernel and a Ryzen 5 7600.

olivierlambert

I'm currently bisecting various kernel builds, I think I'm close to find the culprit.

olivierlambert

Luckily I have enough cores to build a kernel in 2 minutes, because it's been a LOT of them already built to find the culprit

olivierlambert

6.12.90 -> bad
6.12.45 -> bad
6.12.22 -> bad
6.12.11 -> bad
6.12.5 -> bad

BUT 6.12.2 is GOOD! Almost there!

edit: now 6.12.3 is also good. Getting close…

edit: since 6.12.4 is good, then the issue is within 6.12.5. Investigating now.

olivierlambert

Found the culprit, made & tested a patch that works.

Recap at https://notes.vates.tech/share/v5jtq0iytw/p/slow-hvm-boot-on-linux-6-12-5wrvOvZKJ7

I will let the rest of my team to try to get it fixed in upstream.