cvs commit: src/sys/amd64/amd64 mp_machdep.c src/sys/i386/i386 mp_machdep.c

[Colin Percival]

cperciva    2006-04-24 21:17:02 UTC

  FreeBSD src repository

  Modified files:
    sys/amd64/amd64      mp_machdep.c 
    sys/i386/i386        mp_machdep.c 
  Log:
  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.
  
  Revision  Changes    Path
  1.272     +2 -2      src/sys/amd64/amd64/mp_machdep.c
  1.265     +2 -2      src/sys/i386/i386/mp_machdep.c