x86: add_branch_prefix_frag_p() vs PadLock insns

[H.J. Lu]

On Fri, Sep 26, 2025 at 6:29 PM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 26.09.2025 12:21, H.J. Lu wrote:
> > On Fri, Sep 26, 2025, 6:16 PM Jan Beulich <jbeulich@suse.com> wrote:
> >> why is it that add_branch_prefix_frag_p() special-cases PadLock insns?
> >> They're by far not the only ones including prefixes in their opcodes.
> >> IOW - I wonder if the conditional there is either insufficient or
> >> excessive.
> >
> > If I remember correctly, this is to mitigate
> > an Intel processor issue.  No Intel processor
> > support such instructions.
>
> Yes. But then why was the PadLock check added there right when that code
> was introduced? (It has meanwhile been extended, but if that's really
> needed for some reason, it likely wasn't extended enough.)
>
> Jan

This command-line mitigation can be applied to any assembly
codes including padlock which will be skipped.

-- 
H.J.