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| author | cperciva <cperciva@FreeBSD.org> | 2006-04-24 21:17:01 +0000 |
|---|---|---|
| committer | cperciva <cperciva@FreeBSD.org> | 2006-04-24 21:17:01 +0000 |
| commit | 900c1188197bf541f096b7ddf5fdcde20a7a268f (patch) | |
| tree | 4632a5ecc978f4321510ddf43fa5d70cea0575bf /sys | |
| parent | b583a2a9146635170ab1952a6e132407e21da9ed (diff) | |
| download | FreeBSD-src-900c1188197bf541f096b7ddf5fdcde20a7a268f.zip FreeBSD-src-900c1188197bf541f096b7ddf5fdcde20a7a268f.tar.gz | |
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.
Diffstat (limited to 'sys')
| -rw-r--r-- | sys/amd64/amd64/mp_machdep.c | 4 | ||||
| -rw-r--r-- | sys/i386/i386/mp_machdep.c | 4 |
2 files changed, 4 insertions, 4 deletions
diff --git a/sys/amd64/amd64/mp_machdep.c b/sys/amd64/amd64/mp_machdep.c index 7577b62..7ba7643 100644 --- a/sys/amd64/amd64/mp_machdep.c +++ b/sys/amd64/amd64/mp_machdep.c @@ -385,8 +385,8 @@ cpu_mp_start(void) * are available, use them. */ if (cpu_high >= 4) { - /* Ask the processor about up to 32 caches. */ - for (i = 0; i < 32; i++) { + /* Ask the processor about the L1 cache. */ + for (i = 0; i < 1; i++) { cpuid_count(4, i, p); threads_per_cache = ((p[0] & 0x3ffc000) >> 14) + 1; if (hyperthreading_cpus < threads_per_cache) diff --git a/sys/i386/i386/mp_machdep.c b/sys/i386/i386/mp_machdep.c index 1b36f1c..bc5c659 100644 --- a/sys/i386/i386/mp_machdep.c +++ b/sys/i386/i386/mp_machdep.c @@ -434,8 +434,8 @@ cpu_mp_start(void) * are available, use them. */ if (cpu_high >= 4) { - /* Ask the processor about up to 32 caches. */ - for (i = 0; i < 32; i++) { + /* Ask the processor about the L1 cache. */ + for (i = 0; i < 1; i++) { cpuid_count(4, i, p); threads_per_cache = ((p[0] & 0x3ffc000) >> 14) + 1; if (hyperthreading_cpus < threads_per_cache) |
