On 2 March 2018 at 04:34, Alistair Francis <alistai...@gmail.com> wrote:
> On Thu, Mar 1, 2018 at 4:20 PM, Alistair Francis
> <alistair.fran...@xilinx.com> wrote:
>> The cortex A53 TRM specifices that bits 24 and 25 of the L2CTLR register
>> specify the number of cores present and not the number of processors. We
>> have correctly been reporting the number of cores, so just fix the
>> comment to match the TRM.
>>
>> Signed-off-by: Alistair Francis <alistair.fran...@xilinx.com>
>
> Ah! This isn't actually what I want, I want something more like this
> (untested):
>
> commit ce9d9795ebff42e1f742e7dc3786e52524807c65
> Author: Alistair Francis <alist...@alistair23.me>
> Date: Thu Mar 1 20:19:23 2018 -0800
>
> target/arm: Report the number of cores in the cluster
>
> Previously we assumed that we only has a single cluster, which meant we
> could get away with reporting smp_cpus to the guest. There are cases
> where we have two clusters (Xilinx's ZynqMP is a good example) so
> reporting the number of smp_cpus is incorrect. Instead count the cores
> in the cluster.
>
> Signed-off-by: Alistair Francis <alist...@alistair23.me>
>
> diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c
> index 9743bdc..e7b1f3c 100644
> --- a/target/arm/cpu64.c
> +++ b/target/arm/cpu64.c
> @@ -42,8 +42,24 @@ static inline void unset_feature(CPUARMState *env,
> int feature)
> #ifndef CONFIG_USER_ONLY
> static uint64_t a57_a53_l2ctlr_read(CPUARMState *env, const ARMCPRegInfo *ri)
> {
> - /* Number of processors is in [25:24]; otherwise we RAZ */
> - return (smp_cpus - 1) << 24;
> + CPUState *cpu;
> + CPUState *cpu_prev = NULL;
> + int num_cores = 0;
> +
> + /* Figure out the number of cores in the cluster */
> + for (cpu = first_cpu; cpu; cpu = CPU_NEXT(cpu)) {
> + /* Only increase the core count if the CPU we are on is the same
> + * class as the caller and the previous cpu.
> + */
> + if ((CPU_GET_CLASS(cpu) == CPU_GET_CLASS(cpu_prev)) &&
> + (CPU_GET_CLASS(cpu) == CPU_GET_CLASS(CPU(env)))) {
> + num_cores++;
> + }
> + cpu_prev = cpu;
> + }
> +
> + /* Number of cores is in [25:24]; otherwise we RAZ */
> + return num_cores << 24;
> }
> #endif
This seems a bit ad-hoc (it will give the wrong answer if we have
two clusters both of the same kind of CPU, for instance).
Maybe it would be better to have a "cluster-size" property on
the CPU (with the default being number of cores in whole system) ?
thanks
-- PMM
