Commit-ID: f410770293a1fbc08906474c24104a7a11943eb6
Gitweb: http://git.kernel.org/tip/f410770293a1fbc08906474c24104a7a11943eb6
Author: Fenghua Yu <fenghua.yu@xxxxxxxxx>
AuthorDate: Fri, 11 Nov 2016 17:02:38 -0800
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Tue, 15 Nov 2016 18:35:50 +0100
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@xxxxxxxxx>
Cc: "Ravi V Shankar" <ravi.v.shankar@xxxxxxxxx>
Cc: "Tony Luck" <tony.luck@xxxxxxxxx>
Cc: "Sai Prakhya" <sai.praneeth.prakhya@xxxxxxxxx>
Cc: "Vikas Shivappa" <vikas.shivappa@xxxxxxxxxxxxxxx>
Cc: "Ingo Molnar" <mingo@xxxxxxx>
Cc: "H. Peter Anvin" <h.peter.anvin@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1478912558-55514-3-git-send-email-fenghua.yu@xxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 72 ++++++++++++++++----------------
1 file changed, 36 insertions(+), 36 deletions(-)
diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index d6bad09..98edba4 100644
--- 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 */
@@ -781,25 +807,12 @@ static int reset_all_cbms(struct rdt_resource *r)
}
/*
- * 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.
*/
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 = {
--
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