Re: [PATCH 05/10] target/arm: Honour MDCR_EL2.HPMD in Secure EL2

[Richard Henderson]

On 8/11/22 10:16, Peter Maydell wrote:
> The logic in pmu_counter_enabled() for handling the 'prohibit event
> counting' bits MDCR_EL2.HPMD and MDCR_EL3.SPME is written in a way
> that assumes that EL2 is never Secure.  This used to be true, but the
> architecture now permits Secure EL2, and QEMU can emulate this.
>
> Refactor the prohibit logic so that we effectively OR together
> the various prohibit bits when they apply, rather than trying to
> construct an if-else ladder where any particular state of the CPU
> ends up in exactly one branch of the ladder.
>
> This fixes the Secure EL2 case and also is a better structure for
> adding the PMUv8.5 bits MDCR_EL2.HCCD and MDCR_EL3.SCCD.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   target/arm/helper.c | 17 +++++++----------
>   1 file changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index 41def52cf7b..434885d024a 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -1094,7 +1094,7 @@ static bool pmu_counter_enabled(CPUARMState *env, uint8_t 
> counter)
>   {
>       uint64_t filter;
>       bool e, p, u, nsk, nsu, nsh, m;
> -    bool enabled, prohibited, filtered;
> +    bool enabled, prohibited = false, filtered;
>       bool secure = arm_is_secure(env);
>       int el = arm_current_el(env);
>       uint64_t mdcr_el2 = arm_mdcr_el2_eff(env);
> @@ -1112,15 +1112,12 @@ static bool pmu_counter_enabled(CPUARMState *env, 
> uint8_t counter)
>       }
>       enabled = e && (env->cp15.c9_pmcnten & (1 << counter));
>   
> -    if (!secure) {
> -        if (el == 2 && (counter < hpmn || counter == 31)) {
> -            prohibited = mdcr_el2 & MDCR_HPMD;
> -        } else {
> -            prohibited = false;
> -        }
> -    } else {
> -        prohibited = arm_feature(env, ARM_FEATURE_EL3) &&
> -           !(env->cp15.mdcr_el3 & MDCR_SPME);
> +    /* Is event counting prohibited? */
> +    if (el == 2 && (counter < hpmn || counter == 31)) {
> +        prohibited = mdcr_el2 & MDCR_HPMD;
> +    }
> +    if (secure) {
> +        prohibited = prohibited || !(env->cp15.mdcr_el3 & MDCR_SPME);

You can use |= for bool as well.  You don't need the short-circuting of || here.
For consistency, perhaps better to use |= with the first if as well, relying on the 
compiler to fold the initial value false.

But otherwise,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~