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Date: Wed, 26 Apr 2023 19:07:01 +0300
Message-Id: <CS6TEW6NY7FJ.39VTQYTEN8FBH@suppilovahvero>
From: "Jarkko Sakkinen" <jarkko@kernel.org>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: "Thorsten Leemhuis" <regressions@leemhuis.info>, "James Bottomley"
 <James.Bottomley@hansenpartnership.com>, "Vlastimil Babka"
 <vbabka@suse.cz>, "Peter Huewe" <peterhuewe@gmx.de>, "Jason Gunthorpe"
 <jgg@ziepe.ca>, "Jan Dabros" <jsd@semihalf.com>,
 <regressions@lists.linux.dev>, "LKML" <linux-kernel@vger.kernel.org>,
 <linux-integrity@vger.kernel.org>, "Dominik Brodowski"
 <linux@dominikbrodowski.net>, "Herbert Xu" <herbert@gondor.apana.org.au>,
 "Linus Torvalds" <torvalds@linux-foundation.org>, "Johannes Altmanninger"
 <aclopte@gmail.com>
Subject: Re: [REGRESSION] suspend to ram fails in 6.2-rc1 due to tpm errors
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On Wed Apr 26, 2023 at 4:32 AM EEST, Jason A. Donenfeld wrote:
> Nice work! Happy that you got it figured out. That trace seems
> consistent with what I was seeing in my traces, so I think you've
> spotted the right bug.
>
> Jason

Unfortunately there might be two bugs. Unless I interpreted logs
incorrectly also hwrng can race with resume (sorry, I forgot to
save it).

Looking at drivers/char/hw_random/core.c there seems to be no
binding to the PM so I guess that this it supports what I'm
observing [*].

So there's two ways to fix the issue:

1. Unregister hwrng for the course of suspend
2. Add something like TPM_CHIP_SUSPENDED, which is set by suspend and
   cleared by the resume.

I try the 2nd option first because I see it less complicated.
Probably would make sense to turn chip flags as atomic while
at it.

[*] https://elixir.bootlin.com/linux/latest/source/drivers/char/hw_random/c=
ore.c

BR, Jarkko