On Wed, 24 Sep 2014, Andy Lutomirski wrote: > We can sort of fudge it if whatever control BIOS uses is available to > us, too, and we can reprogram it to "enabled" after a microcode update > disables TSX.
Only for the early initramfs microcode update driver, and that's going to be useful only as a way to honor the "keep Intel TSX enabled even if it is badly broken" switch that was added by Intel for developer usage. For the runtime microcode update (regular microcode driver), an "enabled->disabled->enabled" transition would still disrupt the system: triggering a microcode update in a cpu can update other cpus, which might be running Intel TSX instructions. Boom! processes running on these other cpus can crash with SIGILL, and we have data loss. The microcode update has to preserve the entire [visible] processor state, otherwise we cannot safely apply it "late". Intel TSX included. -- "One disk to rule them all, One disk to find them. One disk to bring them all and in the darkness grind them. In the Land of Redmond where the shadows lie." -- The Silicon Valley Tarot Henrique Holschuh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
