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

[Petr Vorel <pvorel@suse.cz>]

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>

...
>  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

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