linux-kernel - Re: [PATCH v3] x86/cpu: Add INTEL_LUNARLAKE_M to X86_BUG

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Message-ID: <c5f9c185-11b1-4bc8-96be-a81895c2a096@intel.com>
Date: Wed, 20 Nov 2024 11:12:17 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Len Brown <lenb@...nel.org>, peterz@...radead.org, tglx@...utronix.de,
 x86@...nel.org
Cc: rafael@...nel.org, linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org, Len Brown <len.brown@...el.com>,
 stable@...r.kernel.org
Subject: Re: [PATCH v3] x86/cpu: Add INTEL_LUNARLAKE_M to X86_BUG_MONITOR

On 11/12/24 18:07, Len Brown wrote:
> From: Len Brown <len.brown@...el.com>
> 
> Under some conditions, MONITOR wakeups on Lunar Lake processors
> can be lost, resulting in significant user-visible delays.
> 
> Add LunarLake to X86_BUG_MONITOR so that wake_up_idle_cpu()
> always sends an IPI, avoiding this potential delay.

This kinda implies that X86_BUG_MONITOR only does one thing.  What about
the two other places in the tree that check it.  Are those relevant?

> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219364
> 
> Cc: stable@...r.kernel.org # 6.11
> Signed-off-by: Len Brown <len.brown@...el.com>

This obviously conflicts with the VFM infrastructure, but shouldn't this
also get backported to even older stable kernels?

I thought the "# 6.11" was to tell folks where it is *needed*, not where
it actually applies.