On Mon, Apr 02, 2018 at 02:44:48PM -0700, Linus Torvalds wrote: > On Mon, Apr 2, 2018 at 2:50 AM, Ingo Molnar <mi...@kernel.org> wrote: > > > > The biggest change is the forcing of asm-goto support on x86, which > > effectively > > increases the GCC minimum supported version to gcc-4.5 (on x86). > > So my biggest worry isn't gcc-4.5 (anybody who hasn't updated deserves > to be forced, or can stay with old kernels). > > No, my biggest worry is clang. What's the status there? > > I've pulled this, and honestly, the disaster with > -fmerge-all-constants makes me think that clang isn't that good a > compiler choice anyway, but it's sad if this undoes a lot of clang > work just because of the worries about Spectre and mis-speculated > branches.
It's not just spectre, I believe you yourself wanted to use asm-goto somewhere in the x86 code: http://lkml.kernel.org/r/CA+55aFyCp-9Qqjcn9wp=vdp2ko7tfyuumjxvkc75xxu0web...@mail.gmail.com There was some KVM talk of relying on it here: http://lkml.kernel.org/r/6a5f2453-cf51-d491-db54-5f239caa2...@redhat.com And there's the comment here: https://elixir.bootlin.com/linux/v4.16-rc7/source/arch/x86/kvm/emulate.c#L457 As to the suitablility of using clang, there's also this unresolved issue: http://lkml.kernel.org/r/20180321211931.ga111...@google.com The fact that even without asm-goto they cannot correctly compile a kernel and have sat on their hands regarding asm-goto for the past 7 odd years makes me care very little. And since they need to spin a new version of the compiler with all the various bugs fixed, they might as well include asm-goto in that and be done with it.
