>>> On 15.03.18 at 17:02, <andrew.coop...@citrix.com> wrote: > On 13/03/18 13:49, Jan Beulich wrote: >> Now that we zero all registers early on all entry paths, use that to >> avoid a couple of immediates here. >> >> Signed-off-by: Jan Beulich <jbeul...@suse.com> >> --- >> We may want to consider eliminating a few more $0 this way. But >> especially for byte ones I'm not sure it's worth it, due to the REX >> prefix the use of %r12 would incur. >> >> --- a/xen/arch/x86/x86_64/compat/entry.S >> +++ b/xen/arch/x86/x86_64/compat/entry.S >> @@ -216,7 +216,7 @@ ENTRY(cstar_enter) >> mov %rcx, STACK_CPUINFO_FIELD(xen_cr3)(%rbx) >> neg %rcx >> mov %rcx, %cr3 >> - movq $0, STACK_CPUINFO_FIELD(xen_cr3)(%rbx) >> + mov %r12, STACK_CPUINFO_FIELD(xen_cr3)(%rbx) > > It is unreasonable to expect people to realise that this use of %r12 is > for a zero, because there is no write to %r12 visible. These need some > kind of comment.
Well, okay, I'll add the same comment in all 7 places. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
