Differential D20192

random: x86 driver: Prefer RDSEED over RDRAND when available
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Authored by cem on May 8 2019, 12:15 AM.

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delphij
markm
imp
jhb
kib
jmg

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O3: Kernel Random Numbers Generator

Commits

rS347239: random: x86 driver: Prefer RDSEED over RDRAND when available

Summary

Per
https://software.intel.com/en-us/blogs/2012/11/17/the-difference-between-rdrand-and-rdseed
, RDRAND is a PRNG seeded from the same source as RDSEED. The source is
more suitable as PRNG seed material, so prefer it when the RDSEED intrinsic
is available (indicated in CPU feature bits).

Test Plan

Bhyve blocks RDSEED feature bit, unfortunately. So I have not tested RDSEED
functionality of this patch yet.

Diff Detail

Repository

rS FreeBSD src repository - subversion

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Event Timeline

cem created this revision.May 8 2019, 12:15 AM

Harbormaster completed remote builds in B24145: Diff 57153.May 8 2019, 12:15 AM

seems sane to me...

This revision is now accepted and ready to land.May 8 2019, 12:17 AM

jhb added inline comments.May 8 2019, 12:22 AM

sys/dev/random/ivy.c
88 ↗	(On Diff #57153)	Maybe "unsupported compiler" or something. I'd honestly just remove the #ifdef and force compile failure though.
108 ↗	(On Diff #57153)	I don't think you need the '!!' since these variables are 'bool'.

jhb added a reviewer: kib.May 8 2019, 12:22 AM

cem added inline comments.May 8 2019, 12:33 AM

sys/dev/random/ivy.c
88 ↗	(On Diff #57153)	Will fix. :)
108 ↗	(On Diff #57153)	Ah, you're totally right. I'll drop that bit.

Drop ifndef wat
Drop bangbang "operator" -- bool implicitly coerces on assignment already

This revision now requires review to proceed.May 8 2019, 12:35 AM

Harbormaster completed remote builds in B24148: Diff 57156.May 8 2019, 12:35 AM

LGTM in principle

This revision is now accepted and ready to land.May 8 2019, 12:35 AM

cem added a parent revision: D20194: vmm(4): Pass through RDSEED feature bit to guests.May 8 2019, 12:38 AM

jhb accepted this revision.May 8 2019, 12:41 AM

Closed by commit rS347239: random: x86 driver: Prefer RDSEED over RDRAND when available (authored by cem). · Explain WhyMay 8 2019, 12:45 AM

This revision was automatically updated to reflect the committed changes.

Owners added a reviewer: O3: Kernel Random Numbers Generator.May 8 2019, 12:45 AM

Herald added a reviewer: jmg. · View Herald TranscriptMay 8 2019, 12:45 AM

Revision Contents
Changeset List

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head/

sys/

dev/

random/

48 lines

O3: Kernel Random Numbers Generator

Diff 57160

head/sys/dev/random/ivy.c

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