Re: [kvm-unit-tests Patch v3 02/11] x86: pmu: Enlarge cnt[] length to 64 in check_counters_many()

[Jim Mattson]

On Tue, Jan 2, 2024 at 7:09 PM Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx> wrote:
>
> Considering there are already 8 GP counters and 4 fixed counters on
> latest Intel processors, like Sapphire Rapids. The original cnt[] array
> length 10 is definitely not enough to cover all supported PMU counters on these
> new processors even through currently KVM only supports 3 fixed counters
> at most. This would cause out of bound memory access and may trigger
> false alarm on PMU counter validation
>
> It's probably more and more GP and fixed counters are introduced in the
> future and then directly extends the cnt[] array length to 64 once and
> for all.
>
> Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
> ---
>  x86/pmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/x86/pmu.c b/x86/pmu.c
> index 0def28695c70..a13b8a8398c6 100644
> --- a/x86/pmu.c
> +++ b/x86/pmu.c
> @@ -254,7 +254,7 @@ static void check_fixed_counters(void)
>
>  static void check_counters_many(void)
>  {
> -       pmu_counter_t cnt[10];
> +       pmu_counter_t cnt[64];

I think 48 should be sufficient, based on the layout of
IA32_PERF_GLOBAL_CTRL and IA32_PERF_GLOBAL_STATUS.

In any event, let's bump this up!

Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>