Re: [PATCH 2/3] x86: Add support for AMD's Automatic IBRS

[Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>]

On Tue, May 30, 2023 at 10:25:36AM +0200, Jan Beulich wrote:
> On 26.05.2023 17:00, Alejandro Vallejo wrote:
> > --- a/xen/arch/x86/smpboot.c
> > +++ b/xen/arch/x86/smpboot.c
> > @@ -376,6 +376,9 @@ void start_secondary(void *unused)
> >      {
> >          wrmsrl(MSR_SPEC_CTRL, default_xen_spec_ctrl);
> >          info->last_spec_ctrl = default_xen_spec_ctrl;
> > +
> > +        if ( cpu_has_auto_ibrs && (default_xen_spec_ctrl & SPEC_CTRL_IBRS) 
> > )
> > +            write_efer(read_efer() | EFER_AIBRSE);
> >      }
> 
> Did you consider using trampoline_efer instead, which would then also take
> care of the S3 resume path (which otherwise I think you'd also need to
> fiddle with)?
> 
> Jan
I didn't because I didn't know about it. Good call though, it's indeed a
better place for it. Will do on v2.

Alejandro