On Wed, 2024-10-02 at 19:56 -0400, Maxim Levitsky wrote:
> While this is not likely, it is valid for the MSR_LBR_TOS
> to contain 0 value, after a test which issues a series of branches, if the
> number of branches recorded was divisible by the number of LBR msrs.
>
> This unfortunately depends on the compiler, the number of LBR registers,
> and it is not even deterministic between different runs of the test,
> because interrupts, rescheduling, and various other events can affect total
> number of branches done.
>
> Therefore drop the check, instead of trying to fix it.
>
> Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
> ---
> x86/pmu_lbr.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/x86/pmu_lbr.c b/x86/pmu_lbr.c
> index c6f010847..8ca8ed044 100644
> --- a/x86/pmu_lbr.c
> +++ b/x86/pmu_lbr.c
> @@ -98,7 +98,6 @@ int main(int ac, char **av)
> lbr_test();
> wrmsr(MSR_IA32_DEBUGCTLMSR, 0);
>
> - report(rdmsr(MSR_LBR_TOS) != 0, "The guest LBR MSR_LBR_TOS value is good.");
> for (i = 0; i < max; ++i) {
> if (!rdmsr(lbr_to + i) || !rdmsr(lbr_from + i))
> break;
A very kind ping on this patch.
Best regards,
Maxim Levitsky
