On Tue, 9 Jan 2018, Linus Torvalds wrote: > On Tue, Jan 9, 2018 at 4:31 PM, Andi Kleen <[email protected]> wrote: > > > > The following patch fixes it for me. Something doesn't > > seem to work with ALTERNATIVE_2. It adds only a few bytes > > more code, so seems acceptable. > > Ugh. It's kind of stupid, though. > > Why is the code sequence not simply: > > ALTERNATIVE "", "lfence", X86_FEATURE_RETPOLINE_AMD > ALTERNATIVE __stringify(jmp *\reg), __stringify(RETPOLINE_JMP \reg), > X86_FEATURE_RETPOLINE > > ie make that X86_FEATURE_RETPOLINE_AMD _only_ emit the "lfence", and > simply fall through to what will be the "jmp *\reg" of the > non-RETPOLINE version. > > Then just make sure X86_FEATURE_RETPOLINE_AMD disables X86_FEATURE_RETPOLINE. > > That is both simpler an dsmaller, no?
Duh, yes.
