x86/intel_rdt: Update percpu closid immeditately on CPUs affected by changee

If CPUs are moved to or removed from a rdtgroup, the percpu closid storage
is updated. If tasks running on an affected CPU use the percpu closid then
the PQR_ASSOC MSR is only updated when the task runs through a context
switch. Up to the context switch the CPUs operate on the wrong closid. This
state is potentially unbound.

Make the change immediately effective by invoking a smp function call on
the affected CPUs which stores the new closid in the perpu storage and
calls the rdt_sched_in() function which updates the MSR, if the current
task uses the percpu closid.

[ tglx: Made it work and massaged changelog once more ]

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Cc: "Ravi V Shankar" <ravi.v.shankar@intel.com>
Cc: "Tony Luck" <tony.luck@intel.com>
Cc: "Sai Prakhya" <sai.praneeth.prakhya@intel.com>
Cc: "Vikas Shivappa" <vikas.shivappa@linux.intel.com>
Cc: "Ingo Molnar" <mingo@elte.hu>
Cc: "H. Peter Anvin" <h.peter.anvin@intel.com>
Link: http://lkml.kernel.org/r/1478912558-55514-3-git-send-email-fenghua.yu@intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index d6bad092f542475e03fb4f2910a51aaf260e266f..98edba4310333038b2976d736c0e3afcb483a89b 100644 (file)
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -191,12 +191,40 @@ static int rdtgroup_cpus_show(struct kernfs_open_file *of,
        return ret;
 }
 
+/*
+ * This is safe against intel_rdt_sched_in() called from __switch_to()
+ * because __switch_to() is executed with interrupts disabled. A local call
+ * from rdt_update_percpu_closid() is proteced against __switch_to() because
+ * preemption is disabled.
+ */
+static void rdt_update_cpu_closid(void *v)
+{
+       this_cpu_write(cpu_closid, *(int *)v);
+       /*
+        * We cannot unconditionally write the MSR because the current
+        * executing task might have its own closid selected. Just reuse
+        * the context switch code.
+        */
+       intel_rdt_sched_in();
+}
+
+/* Update the per cpu closid and eventually the PGR_ASSOC MSR */
+static void rdt_update_percpu_closid(const struct cpumask *cpu_mask, int closid)
+{
+       int cpu = get_cpu();
+
+       if (cpumask_test_cpu(cpu, cpu_mask))
+               rdt_update_cpu_closid(&closid);
+       smp_call_function_many(cpu_mask, rdt_update_cpu_closid, &closid, 1);
+       put_cpu();
+}
+
 static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of,
                                   char *buf, size_t nbytes, loff_t off)
 {
        cpumask_var_t tmpmask, newmask;
        struct rdtgroup *rdtgrp, *r;
-       int ret, cpu;
+       int ret;
 
        if (!buf)
                return -EINVAL;
@@ -236,8 +264,7 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of,
                /* Give any dropped cpus to rdtgroup_default */
                cpumask_or(&rdtgroup_default.cpu_mask,
                           &rdtgroup_default.cpu_mask, tmpmask);
-               for_each_cpu(cpu, tmpmask)
-                       per_cpu(cpu_closid, cpu) = 0;
+               rdt_update_percpu_closid(tmpmask, rdtgroup_default.closid);
        }
 
        /*
@@ -251,8 +278,7 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of,
                                continue;
                        cpumask_andnot(&r->cpu_mask, &r->cpu_mask, tmpmask);
                }
-               for_each_cpu(cpu, tmpmask)
-                       per_cpu(cpu_closid, cpu) = rdtgrp->closid;
+               rdt_update_percpu_closid(tmpmask, rdtgroup_default.closid);
        }
 
        /* Done pushing/pulling - update this group with new mask */
@@ -780,18 +806,6 @@ static int reset_all_cbms(struct rdt_resource *r)
        return 0;
 }
 
-/*
- * MSR_IA32_PQR_ASSOC is scoped per logical CPU, so all updates
- * are always in thread context.
- */
-static void rdt_reset_pqr_assoc_closid(void *v)
-{
-       struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
-
-       state->closid = 0;
-       wrmsr(MSR_IA32_PQR_ASSOC, state->rmid, 0);
-}
-
 /*
  * Forcibly remove all of subdirectories under root.
  */
@@ -799,7 +813,6 @@ static void rmdir_all_sub(void)
 {
        struct rdtgroup *rdtgrp, *tmp;
        struct task_struct *p, *t;
-       int cpu;
 
        /* move all tasks to default resource group */
        read_lock(&tasklist_lock);
@@ -807,14 +820,6 @@ static void rmdir_all_sub(void)
                t->closid = 0;
        read_unlock(&tasklist_lock);
 
-       get_cpu();
-       /* Reset PQR_ASSOC MSR on this cpu. */
-       rdt_reset_pqr_assoc_closid(NULL);
-       /* Reset PQR_ASSOC MSR on the rest of cpus. */
-       smp_call_function_many(cpu_online_mask, rdt_reset_pqr_assoc_closid,
-                              NULL, 1);
-       put_cpu();
-
        list_for_each_entry_safe(rdtgrp, tmp, &rdt_all_groups, rdtgroup_list) {
                /* Remove each rdtgroup other than root */
                if (rdtgrp == &rdtgroup_default)
@@ -828,15 +833,13 @@ static void rmdir_all_sub(void)
                cpumask_or(&rdtgroup_default.cpu_mask,
                           &rdtgroup_default.cpu_mask, &rdtgrp->cpu_mask);
 
+               rdt_update_percpu_closid(&rdtgrp->cpu_mask,
+                                        rdtgroup_default.closid);
+
                kernfs_remove(rdtgrp->kn);
                list_del(&rdtgrp->rdtgroup_list);
                kfree(rdtgrp);
        }
-
-       /* Reset all per cpu closids to the default value */
-       for_each_cpu(cpu, &rdtgroup_default.cpu_mask)
-               per_cpu(cpu_closid, cpu) = 0;
-
        kernfs_remove(kn_info);
 }
 
@@ -943,7 +946,6 @@ static int rdtgroup_rmdir(struct kernfs_node *kn)
 {
        struct task_struct *p, *t;
        struct rdtgroup *rdtgrp;
-       int cpu, ret = 0;
 
        rdtgrp = rdtgroup_kn_lock_live(kn);
        if (!rdtgrp) {
@@ -962,8 +964,7 @@ static int rdtgroup_rmdir(struct kernfs_node *kn)
        /* Give any CPUs back to the default group */
        cpumask_or(&rdtgroup_default.cpu_mask,
                   &rdtgroup_default.cpu_mask, &rdtgrp->cpu_mask);
-       for_each_cpu(cpu, &rdtgrp->cpu_mask)
-               per_cpu(cpu_closid, cpu) = 0;
+       rdt_update_percpu_closid(&rdtgrp->cpu_mask, rdtgroup_default.closid);
 
        rdtgrp->flags = RDT_DELETED;
        closid_free(rdtgrp->closid);
@@ -977,8 +978,7 @@ static int rdtgroup_rmdir(struct kernfs_node *kn)
        kernfs_remove(rdtgrp->kn);
 
        rdtgroup_kn_unlock(kn);
-
-       return ret;
+       return 0;
 }
 
 static struct kernfs_syscall_ops rdtgroup_kf_syscall_ops = {