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

From: Dave Hansen <dave.hansen@intel.com>
To: Kalle Valo <kvalo@kernel.org>, Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	x86@kernel.org, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org, regressions@lists.linux.dev,
	Jeff Johnson <quic_jjohnson@quicinc.com>,
	Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
	Daniel Sneddon <daniel.sneddon@linux.intel.com>
Subject: Re: [regression] suspend stress test stalls within 30 minutes
Date: Tue, 14 May 2024 09:10:07 -0700	[thread overview]
Message-ID: <feaefaae-e25b-4a48-b6be-e20054f2c8df@intel.com> (raw)
In-Reply-To: <874jb0jzx5.fsf@kernel.org>

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.