K 10
svn:author
V 8
cperciva
K 8
svn:date
V 27
2006-04-24T21:17:01.000000Z
K 7
svn:log
V 678
Adjust dangerous-shared-cache-detection logic from "all shared data
caches are dangerous" to "a shared L1 data cache is dangerous".  This
is a compromise between paranoia and performance: Unlike the L1 cache,
nobody has publicly demonstrated a cryptographic side channel which
exploits the L2 cache -- this is harder due to the larger size, lower
bandwidth, and greater associativity -- and prohibiting shared L2
caches turns Intel Core Duo processors into Intel Core Solo processors.

As before, the 'machdep.hyperthreading_allowed' sysctl will allow even
the L1 data cache to be shared.

Discussed with:	jhb, scottl
Security:	See FreeBSD-SA-05:09.htt for background material.

END