On Wed, 10 Jan 2018, Borislav Petkov wrote: > On Wed, Jan 10, 2018 at 07:20:13AM +0100, Ingo Molnar wrote: > > it be really unreasonable to say that if a microcode update changes CPU > > flags an initrd rebuild and a reboot is required? It's not like microcode > > updates > > are _that_ frequent - in fact they tend to be much _less_ frequent in a > > system's > > life time than kernel updates. > > > > So all of this 'late loading' and CPU flag splitting complexity seems > > unnecessary > > to me: we should be glad we do early microcode loading now, and should > > embrace it. > > > > Changing CPU features way after the CPU has booted up is possible, and we > > could in > > theory extend code patching to work 'late' as well, but given how > > infrequent all > > this is bound to be in practice I fear it's all going to be a big, seldom > > tested, > > often broken mess, with no real benefit to users. > > Agreed: we support that late patching for those use cases where machines > run for a long time, simulating all kinds of crap. And frankly, if > those things need to get IBRS all of a sudden and *not* reboot, then > something's wrong with the whole contraption setup. > > So yes, I'd vote too for supporting only early IBRS and not do the late > thing now. Maybe later, if there's, like, a really compelling use case.
/me exposes it to the flame-thrower
