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Subject[PATCH 06/32] x86/intel_rdt: Hot cpu support for Cache Allocation
Date
From: Vikas Shivappa <vikas.shivappa@linux.intel.com>

This patch adds hot plug cpu support for Intel Cache allocation. Support
includes updating the cache bitmask MSRs IA32_L3_QOS_n when a new CPU
package comes online or goes offline. The IA32_L3_QOS_n MSRs are one per
Class of service on each CPU package. The new package's MSRs are
synchronized with the values of existing MSRs. Also the software cache
for IA32_PQR_ASSOC MSRs are reset during hot cpu notifications.

Signed-off-by: Vikas Shivappa <vikas.shivappa@linux.intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
---
arch/x86/kernel/cpu/intel_rdt.c | 76 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 76 insertions(+)

diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
index 8379df8..31f8588 100644
--- a/arch/x86/kernel/cpu/intel_rdt.c
+++ b/arch/x86/kernel/cpu/intel_rdt.c
@@ -24,6 +24,7 @@

#include <linux/slab.h>
#include <linux/err.h>
+#include <linux/cpu.h>
#include <linux/sched.h>
#include <asm/pqr_common.h>
#include <asm/intel_rdt.h>
@@ -234,6 +235,75 @@ static inline bool rdt_cpumask_update(int cpu)
return false;
}

+/*
+ * cbm_update_msrs() - Updates all the existing IA32_L3_MASK_n MSRs
+ * which are one per CLOSid on the current package.
+ */
+static void cbm_update_msrs(void *dummy)
+{
+ int maxid = boot_cpu_data.x86_cache_max_closid;
+ struct rdt_remote_data info;
+ unsigned int i;
+
+ for (i = 0; i < maxid; i++) {
+ if (cctable[i].clos_refcnt) {
+ info.msr = CBM_FROM_INDEX(i);
+ info.val = cctable[i].l3_cbm;
+ msr_cpu_update(&info);
+ }
+ }
+}
+
+static inline void intel_rdt_cpu_start(int cpu)
+{
+ struct intel_pqr_state *state = &per_cpu(pqr_state, cpu);
+
+ state->closid = 0;
+ mutex_lock(&rdt_group_mutex);
+ if (rdt_cpumask_update(cpu))
+ smp_call_function_single(cpu, cbm_update_msrs, NULL, 1);
+ mutex_unlock(&rdt_group_mutex);
+}
+
+static void intel_rdt_cpu_exit(unsigned int cpu)
+{
+ int i;
+
+ mutex_lock(&rdt_group_mutex);
+ if (!cpumask_test_and_clear_cpu(cpu, &rdt_cpumask)) {
+ mutex_unlock(&rdt_group_mutex);
+ return;
+ }
+
+ cpumask_and(&tmp_cpumask, topology_core_cpumask(cpu), cpu_online_mask);
+ cpumask_clear_cpu(cpu, &tmp_cpumask);
+ i = cpumask_any(&tmp_cpumask);
+
+ if (i < nr_cpu_ids)
+ cpumask_set_cpu(i, &rdt_cpumask);
+ mutex_unlock(&rdt_group_mutex);
+}
+
+static int intel_rdt_cpu_notifier(struct notifier_block *nb,
+ unsigned long action, void *hcpu)
+{
+ unsigned int cpu = (unsigned long)hcpu;
+
+ switch (action) {
+ case CPU_DOWN_FAILED:
+ case CPU_ONLINE:
+ intel_rdt_cpu_start(cpu);
+ break;
+ case CPU_DOWN_PREPARE:
+ intel_rdt_cpu_exit(cpu);
+ break;
+ default:
+ break;
+ }
+
+ return NOTIFY_OK;
+}
+
static int __init intel_rdt_late_init(void)
{
struct cpuinfo_x86 *c = &boot_cpu_data;
@@ -261,9 +331,15 @@ static int __init intel_rdt_late_init(void)
goto out_err;
}

+ cpu_notifier_register_begin();
+
for_each_online_cpu(i)
rdt_cpumask_update(i);

+ __hotcpu_notifier(intel_rdt_cpu_notifier, 0);
+
+ cpu_notifier_register_done();
+
static_key_slow_inc(&rdt_enable_key);
pr_info("Intel cache allocation enabled\n");
out_err:
--
2.5.0
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