On 01/11/17 12:54, gengdongjiu wrote: > Hi Robin, > > On 2017/11/1 19:24, Robin Murphy wrote: >>> + esb >>> +alternative_else_nop_endif >>> +1: >>> + .endm >> Having a branch in here is pretty horrible, and furthermore using label >> number 1 has a pretty high chance of subtly breaking code where this >> macro is inserted. >> >> Can we not somehow nest or combine the alternative conditions here? > > I found it will report error if combine the alternative conditions here. > > For example: > > + .macro error_synchronize > +alternative_if ARM64_HAS_IESB > +alternative_if ARM64_HAS_RAS_EXTN > + esb > +alternative_else_nop_endif > +alternative_else_nop_endif > + .endm > > And even using b.eq/cbz instruction in the alternative instruction in > arch/arm64/kernel/entry.S, > it will report Error. > > For example below > > alternative_if ARM64_HAS_PAN > xxxxxxxxxxxxxxxxxxxx > b.eq xxxxx > alternative_else_nop_endif > > I do not dig it deeply, do you know the reason about it or good suggestion > about that? > Thanks a lot in advance.
Actually, on second look ARM64_HAS_RAS_EXTN doesn't even matter - ESB is a hint, so if the CPU doesn't have RAS it should behave as a NOP anyway. On which note, since I don't see one here - are any of those other patches defining an "esb" assembly macro similar to the inline asm case? If not then this isn't going to build with older toolchains - perhaps we should just use the raw hint syntax directly. Robin. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
