Subject: Re: Fwd: High cpu usage caused by kernel process when upgraded to linux 5.19.17 or later

From: Thomas Gleixner <[email-masked]>
Date: Thu, 29 Jun 2023 16:18:57 +0200

On Thu, Jun 29 2023 at 12:05, Vivek Anand wrote:
> I've tried booting with "spectre_v2=retpoline retbleed=off".
> This change didn't work. Still CPU is 100%

This does not make sense.

retbleed=off has the same effect as CONFIG_X86_IBRS_ENTRY=n.

The only difference is that with CONFIG_X86_IBRS_ENTRY=y and
retbleed=off there is one extra jump in the low level entry code
(syscall, interrupts, exceptions) and one extra jump on the exit side.

But those extra jumps are completely irrelevant for the kworker threads.

Can you please provide dmesg and the content of the files in

 /sys/devices/system/cpu/vulnerabilities/

on a kernel booted with "spectre_v2=retpoline retbleed=off" ?

Thanks,

        tglx