On Wed, Nov 01, 2017 at 08:54:44PM +0800, gengdongjiu wrote: > 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. Alternatives cannot be nested. You need to define a cap like: ARM64_HAS_RAS_NOT_IESB ... which is set when ARM64_HAS_RAS_EXTN && !ARM64_HAS_IESB. Then you can do: alternative_if ARM64_HAS_RAS_NOT_IESB esb alternative_else_nop_endif See ARM64_ALT_PAN_NOT_UAO for an example. That said, as Robin points out we may not even need the alternative. Thanks, Mark. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
