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RDSEED support for the Linux kernel

From:  "H. Peter Anvin" <>
To:  Linus Torvalds <>, Ted Ts'o <>, "H. Peter Anvin" <>, Ingo Molnar <>, Thomas Gleixner <>
Subject:  [PATCH 0/3] RDSEED support for the Linux kernel
Date:  Tue, 4 Mar 2014 14:40:12 -0800
Message-ID:  <>
Cc:  Linux Kernel Mailing List <>, "H. Peter Anvin" <>
Archive-link:  Article

From: "H. Peter Anvin" <>

Upcoming Intel silicon adds a new RDSEED instruction.  Whereas RDRAND
returns output from a PRNG, the RDSEED instruction returns fully
conditioned entropy that is suitable for use as seeds to a PRNG.

This patchset adds support for RDSEED in the Linux kernel in three

1. During bootup, use RDSEED to initialize the entropy pool if
   available (we already use RDRAND for this).  We don't add any
   credit at this point, but it will give much better starting point.

2. In the slow path to add_interrupt_randomness, executed once per
   second, we take a single RDSEED sample and mix it into the entropy
   pool, crediting it at 50% of its rated entropy.  This was suggested
   by Linus.

3. If we are about to block on /dev/random due to lack of entropy,
   attempt an "emergency pool refill" using RDSEED.

Comments are, of course, appreciated.


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