On Thu, 2018-01-11 at 18:05 +0100, Peter Zijlstra wrote: > On Thu, Jan 11, 2018 at 06:01:23PM +0100, Jiri Kosina wrote: > > On Thu, 11 Jan 2018, Josh Poimboeuf wrote: > > > > > I think I heard that retpolines won't be ported to anything older than > > > GCC 4.9, so maybe it's safe to use '%='. I don't remember when it was > > > introduced into GCC though. > > > > I'm afraid we'll have to backport retpolines in some form to 4.3.x at > > least. I'd be surprised if we'd be the only ones on this planet :) > > So upstream code is going to require 4.5 at least, and 4.4 has %=. > Backport effort will just have to cope or backport more GCC bits, that > is, if you're backporting retpoline to 4.3 also backport asm-goto.
Again, the RSB thing is for more than just retpoline; it's needed for IBRS support too and that *doesn't* necessarily require a newer compiler at all. But really, if %= is supported at least as far back as 4.4 (and maybe further?) then I'm not going to care about it unless someone really screams. I think we're fairly much done, unless Andi you really want to make the RSB stuffing code out-of-line? Thomas, do you want to leave Josh's patches on top with a revert, as they are at the moment in my tree, or rebase and fold them in as we go?
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