On 15/03/18 16:39, Jan Beulich wrote: >>>> 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.
With that change, Acked-by: Andrew Cooper <andrew.coop...@citrix.com> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
