On Fri, 26 Mar 2010 14:39:56 +0100
Borislav Petkov <bp@xxxxxxxxx> wrote:
> From: Borislav Petkov <borislav.petkov@xxxxxxx>
>
> Starting with F10h, revE, AMD processors add support for a dynamic
> core boosting feature called Core Performance Boost. When a specific
> condition is present, a subset of the cores on a system are boosted
> beyond their P0 operating frequency to speed up the performance of
> single-threaded applications.
>
> In the normal case, the system comes out of reset with core boosting
> enabled. This patch adds a sysfs knob with which core boosting can be
> switched on or off for benchmarking purposes.
>
> While at it, cleanup the driver init codepath and update copyrights.
>
> ...
>
> +static void _cpb_toggle_msrs(bool t)
> +{
> + int cpu;
> +
> + rdmsr_on_cpus(cpu_online_mask, MSR_K7_HWCR, msrs);
> +
> + for_each_cpu(cpu, cpu_online_mask) {
> + struct msr *reg = per_cpu_ptr(msrs, cpu);
> + if (t)
> + reg->l &= ~BIT(25);
> + else
> + reg->l |= BIT(25);
> + }
> + wrmsr_on_cpus(cpu_online_mask, MSR_K7_HWCR, msrs);
> +}
What prevents cpu_online_mask from changing while this is happening?
> @@ -1422,15 +1490,34 @@ static int __cpuinit powernowk8_init(void)
> supported_cpus++;
> }
>
> - if (supported_cpus == num_online_cpus()) {
> - printk(KERN_INFO PFX "Found %d %s "
> - "processors (%d cpu cores) (" VERSION ")\n",
> - num_online_nodes(),
> - boot_cpu_data.x86_model_id, supported_cpus);
> - return cpufreq_register_driver(&cpufreq_amd64_driver);
> + if (supported_cpus != num_online_cpus())
> + return -ENODEV;
> +
> + printk(KERN_INFO PFX "Found %d %s (%d cpu cores) (" VERSION ")\n",
> + num_online_nodes(), boot_cpu_data.x86_model_id, supported_cpus);
> +
> + if (boot_cpu_has(X86_FEATURE_CPB)) {
> +
> + cpb_capable = true;
> +
> + msrs = msrs_alloc();
> + if (!msrs) {
> + printk(KERN_ERR "%s: Error allocating msrs!\n", __func__);
> + return -ENOMEM;
> + }
> +
> + rdmsr_on_cpus(cpu_online_mask, MSR_K7_HWCR, msrs);
> +
> + for_each_cpu(cpu, cpu_online_mask) {
> + struct msr *reg = per_cpu_ptr(msrs, cpu);
> + cpb_enabled |= !(!!(reg->l & BIT(25)));
> + }
Ditto.
I assume these changes get applied to new CPUs as they come online?
> ...
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