[LTP] [PATCH] tracing/pt_test: TCONF if Intel PT across VMXON is not supported

[Jan Stancek]

On Mon, Mar 17, 2025 at 1:24 PM Petr Vorel <pvorel@suse.cz> wrote:
>
> Hi Jan,
>
> > As noted in 1c5ac21a0e9b ("perf/x86/intel/pt: Don't die on VMXON"),
> > some Broadwell systems don't support Intel PT across VMXON.
> +1
>
> > If the test fails to find any events, check whether there is a
> > kvm_intel module loaded, and if so check for IA32_VMX_MISC[bit 14].
> > If this bit is 0, it's not supported. From commit mentioned above:
> >     Intel SDM, 36.5 "Tracing post-VMXON" says that
> >     "IA32_VMX_MISC[bit 14]" being 1 means PT can trace
> >     post-VMXON.
>
> LGTM.
>
> Reviewed-by: Petr Vorel <pvorel@suse.cz>

Pushed with the string joined.

Thanks,
Jan

>
> ...
> >  static void intel_pt_trace_check(void)
> >  {
> >       uint64_t aux_head = 0;
> > @@ -117,6 +150,12 @@ static void intel_pt_trace_check(void)
> >       pmp = (struct perf_event_mmap_page *)bufm[0];
> >       aux_head = *(volatile uint64_t *)&pmp->aux_head;
> >       if (aux_head == 0) {
> > +             if ((access("/sys/module/kvm_intel", F_OK) == 0)
> > +                     && (!is_supported_across_vmxon())) {
> > +                     tst_brk(TCONF, "Intel PT on this system can not"
> > +                             " run at the same time as virtualization");
>
> As we discussed at the issue, please join the string before merge.
>
> Kind regards,
> Petr
>