Re: [PATCH v2 00/13] objtool: Detect and warn about indirect calls in __nocfi functions

Peter Zijlstra
2025-05-02T11:08:30Z

On Thu, May 01, 2025 at 08:33:57PM +0200, Paolo Bonzini wrote:
> On Wed, Apr 30, 2025 at 1:26 PM Peter Zijlstra <peterz@infradead.org> wrote:
> > Notably the KVM fastop emulation stuff -- which I've completely rewritten for
> > this version -- the generated code doesn't look horrific, but is slightly more
> > verbose. I'm running on the assumption that instruction emulation is not super
> > performance critical these days of zero VM-exit VMs etc.
>
> It's definitely going to be slower, but I guess it's okay these days.

Yeah, it adds a bunch of branches at the very least. But that was indeed
the argument, we shouldn't care much these days.

> It's really only somewhat hot with really old processors
> (pre-Westmere) and only when running big real mode code.

Right, really old stuff :-)