On Sun, 18 Nov 2018, Tim Chen wrote: > On 11/18/2018 02:17 PM, Jiri Kosina wrote: > > On Sun, 18 Nov 2018, Linus Torvalds wrote: > > > >>> So, I think it's as theoretical as any other spectrev2 (only with the > >>> extra "HT" condition added on top). > >> > >> What? No. > >> > >> It's *way* more theoretical than something like meltdown, which could > >> be trivially used to get data from another protection domain. > > > > Oh yeah, I absolutely agree that spectrev2 and Meltdown and completely > > different beasts. > > > >> Have you seen any actual realistic attacks for normal human users? > >> Things where the *kernel* should actually care? > >> > >> The javascript thing is for the browser to fix up, > > > > It's probably not just browsers, but anything running JITed sandboxed > > code. So the most straightforward way might be the prctl() aproach, where > > userspace would claim "I do care about this, please fix it up for me". So > > prctl() + perhaps SECCOMP. > > > > Which gets us back to Tim's fixup patch. Do you still prefer the revert, > > given the existence of that? I think that if Tim's fixup makes it through > > (it's currently missing SECCOMP handling, but that is trivial to add on > > top), it might be the best compromise. We'd also have have to make IBPB > > obey it to be consistent (and get even a few more % of performance back), > > but that's easy as well. > > > I think if Thomas can merge my patchset along with Jiri's, the default > option will become opt in for tasks that want the extra security and we > won't lose performance. If it would be in mergeable state .... Thanks, tglx
