RE: [REGRESSION][BISECTED] Boot stall from merge tag 'net-next-6.2'

From: David Laight <David.Laight@ACULAB.COM>
To: 'Linus Torvalds' <torvalds@linux-foundation.org>,
	Ard Biesheuvel <ardb@kernel.org>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>,
	"regressions@leemhuis.info" <regressions@leemhuis.info>,
	Andrew Lunn <andrew@lunn.ch>,
	Linux Stable <stable@vger.kernel.org>,
	Linux Regressions <regressions@lists.linux.dev>,
	Bagas Sanjaya <bagasdotme@gmail.com>,
	Sami Korkalainen <sami.korkalainen@proton.me>
Subject: RE: [REGRESSION][BISECTED] Boot stall from merge tag 'net-next-6.2'
Date: Sun, 25 Jun 2023 15:36:34 +0000	[thread overview]
Message-ID: <be98e9a82acc4a099026eca1e22f5a80@AcuMS.aculab.com> (raw)
In-Reply-To: <CAHk-=whKF0S33EgXts++dpspdFAtkf_otRbV45x1Yt2+bDz0sQ@mail.gmail.com>

From: Linus Torvalds
> Sent: 24 June 2023 00:03
> 
> On Fri, 23 Jun 2023 at 15:55, Ard Biesheuvel <ardb@kernel.org> wrote:
> >
> > With the revert applied, the kernel/EFI stub only consumes the
> > variable and deletes it, but never creates it by itself, and so the
> > code does nothing if the variable is never created in the first place.
> 
> Right.
> 
> But my *point* was that if we want to create it, we DAMN WELL DO NOT
> WANT TO DO SO AT BOOT TIME.
> 
> Boot time is absolutely the worst possible time to do it.
> 
> We'd be much better off doing so at shutdown time, when we at least
> have (a) maximal entropy and (b) failures are less critical.

Or maybe better - especially for embedded systems which don't
often get shut down properly (or any where someone can force
a system crash and then get no saved entropy) - after the system
has been running long enough to get a reasonable amount of
entropy.

Also, why delete the entropy during boot?
Clearly it is sub-optimal to use it twice, but that has to
be better that not using any at all?

	David

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