DragonFly kernel List (threaded) for 2004-06
Re: Opteron bugs
:Since amd64 is a future target, it may be worthwhile to note these
:'AMD has pledged to fix three bugs in its Opteron chips that, if
:unremedied, could cause host systems to crash in certain circumstances.
:In a June 2004 Opteron and Athlon 64 Revision Guide (PDF), the chip
:maker lists three processor glitches - known in the trade as 'errata' -
:that could mean the "system may hang".'
The first one might allow a user to intentionally crash a machine,
but no normal code will ever generate those circumstances.
The second one is s non-starter. Kernel developers already know all
about livelocking cpus on mutex spin operations. No such situations
exist in DragonFly.
The rep/movs issue is more problematic but, again, it is not a
sequence that the compiler normally generates. The compiler will
use rep/movs to copy structures, but it does so in the forward
direction and the bug only occurs with reverse direction copies.
The FreeBSD kernel bcopy code uses a std/rep/movs sequence but I actually
ripped that out of DragonFly over a month ago when I redid DFly's
optimized bcopy/bzero code.
There are lots of errata (In the low hundreds) for both Intel and
AMD cpus, but 99.5% of them are related to circumstances that cannot
occur under normal system operation.