linux-kernel - Re: [PATCH v3 0/3] SRF: Fix offline CPU preventing pc6 entry

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Message-ID: <15d18759-68eb-4683-9255-715545505ed6@linux.intel.com>
Date: Thu, 14 Nov 2024 18:13:39 +0100
From: Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
 rafael.j.wysocki@...el.com, len.brown@...el.com,
 artem.bityutskiy@...ux.intel.com, dave.hansen@...ux.intel.com,
 Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 0/3] SRF: Fix offline CPU preventing pc6 entry

> That's not really working:
>
>   1) Regular kexec offlines them again.

But then, they execute hlt loop in the reboot vector right?
I think that's fine. We just don't want to be woken up from the mwait
when the RIP points to garbage.

>   2) Kexec in panic can't do any of that.

Does it make sense to change the kexec, so that every CPU is forced
into the reboot vector, which I believe happens for online CPUs?
We don't have to online them all the way. Maybe minimal bringup just
to be able to send them the IPI?

As a side note, It's not that important for this patchset. I think I
can make it work without simplifying the existing hack, but crossed my
mind at some point that maybe we could do that.