Re: [PATCH -tip v3 1/2] x86: xen: insn: Decode Xen and KVM emulate-prefix signature

Peter Zijlstra
2019-09-06T09:15:37Z

On Fri, Sep 06, 2019 at 05:51:43PM +0900, Masami Hiramatsu wrote:
> On Fri, 6 Sep 2019 17:45:19 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> > >
> > > How about we make this asm/virt_prefix.h or something and include:
> > >
> > > /*
> > > * Virt escape sequences to trigger instruction emulation;
> > > * ideally these would decode to 'whole' instruction and not destroy
> > > * the instruction stream; sadly this is not true for the 'kvm' one :/
> > > */
> > >
> > > #define __XEN_EMULATE_PREFIX 0x0f,0x0b,0x78,0x65,0x6e /* ud2 ; .ascii "xen" */
> > > #define __KVM_EMULATE_PREFIX 0x0f,0x0b,0x6b,0x76,0x6d /* ud2 ; .ascii "kvm" */
>
> BTW, what should we call it, "emulate prefix" or "virt prefix"?
> "virt prefix" sounds too generic to me. So I rather like emulate_prefix.h.

Works for me; and yeah, just see what is best for the other things. I
only started down that road because the Xen and KVM 'prefixes' were
initialized so inconsistently.