linux-kernel - Re: [regression] suspend stress test stalls within 30 minutes

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Date: Tue, 14 May 2024 09:10:07 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Kalle Valo <kvalo@...nel.org>, Borislav Petkov <bp@...en8.de>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 "Rafael J. Wysocki" <rafael@...nel.org>, x86@...nel.org,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 regressions@...ts.linux.dev, Jeff Johnson <quic_jjohnson@...cinc.com>,
 Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
 Daniel Sneddon <daniel.sneddon@...ux.intel.com>
Subject: Re: [regression] suspend stress test stalls within 30 minutes

On 5/14/24 06:17, Kalle Valo wrote:
> The kernel we use in our ath11k testing has almost all kernel debug
> features enabled so I decided disable all of them, which unsurprisingly
> also fixed my suspend problems. So maybe this is something which happens
> only when MITIGATION_IBRS_ENTRY and some debug option from 'Kernel
> hacking' are both enabled?

I had my money on DEBUG_ENTRY, but it doesn't look like you ever had it
enabled.

I've got basically two theories:

One, the IBRS value is getting mucked up somewhere, either that %r15
value is getting stepped on or the per-cpu value is corrupt and the
WRMSR #GP's, causing the hang.

Two, IBRS_{ENTER,EXIT} is called in a "wrong" context somewhere.  Either
it is clobbering something it shouldn't or it is assuming something is
in place that is not (like a valid stack).

But the whole "'sudo shutdown -h now' then suspend somehow immediately
unstalls" thing is really perplexing.  I hope Pawan has some ideas.