linux-kernel - Re: random(4) changes

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Message-ID: <20160426184439.GA8162@amd>
Date:	Tue, 26 Apr 2016 20:44:39 +0200
From:	Pavel Machek <pavel@....cz>
To:	Theodore Ts'o <tytso@....edu>,
	Stephan Mueller <smueller@...onox.de>,
	Sandy Harris <sandyinchina@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-crypto@...r.kernel.org, Jason Cooper <jason@...edaemon.net>,
	John Denker <jsd@...n.com>, "H. Peter Anvin" <hpa@...or.com>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: random(4) changes

Hi1

> > When dropping the add_disk_randomness function in the legacy /dev/random, I 
> > would assume that without changes to add_input_randomness and 
> > add_interrupt_randomness, we become even more entropy-starved.
> 
> Sure, but your system isn't doing anything magical here.  The main
> difference is that you assume you can get almost a full bit of entropy
> out of each interrupt timing, where I'm much more conservative and
> assume we can only get 1/64th of a bit out of each interrupt timing.

Maybe 1/64th of a bit is a bit too conservative? I guess we really
have more than one bit of entropy on any system with timestamp
counter....

Making it 1/2 of bit (or something) should be very easy way to improve
entropy early during boot...

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html