linux-kernel - [PATCH 28/32] x86/intel_rdt_rdtgroup.c: Read and write cpus

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Message-Id: <1468371785-53231-29-git-send-email-fenghua.yu@intel.com>
Date:	Tue, 12 Jul 2016 18:03:01 -0700
From:	"Fenghua Yu" <fenghua.yu@...el.com>
To:	"Thomas Gleixner" <tglx@...utronix.de>,
	"Ingo Molnar" <mingo@...e.hu>,
	"H. Peter Anvin" <h.peter.anvin@...el.com>,
	"Tony Luck" <tony.luck@...el.com>, "Tejun Heo" <tj@...nel.org>,
	"Borislav Petkov" <bp@...e.de>,
	"Stephane Eranian" <eranian@...gle.com>,
	"Peter Zijlstra" <peterz@...radead.org>,
	"Marcelo Tosatti" <mtosatti@...hat.com>,
	"David Carrillo-Cisneros" <davidcc@...gle.com>,
	"Ravi V Shankar" <ravi.v.shankar@...el.com>,
	"Vikas Shivappa" <vikas.shivappa@...ux.intel.com>,
	"Sai Prakhya" <sai.praneeth.prakhya@...el.com>
Cc:	"linux-kernel" <linux-kernel@...r.kernel.org>,
	"x86" <x86@...nel.org>, "Fenghua Yu" <fenghua.yu@...el.com>
Subject: [PATCH 28/32] x86/intel_rdt_rdtgroup.c: Read and write cpus

From: Fenghua Yu <fenghua.yu@...el.com>

Normally each task is associated with one rdtgroup and we use the schema
for that rdtgroup whenever the task is running. The user can designate
some cpus to always use the same schema, regardless of which task is
running. To do that the user write a cpumask bit string to the "cpus"
file.

A cpu can only be listed in one rdtgroup. If the user specifies a cpu
that is currently assigned to a different rdtgroup, it is removed
from that rdtgroup.

See Documentation/x86/intel_rdt_ui.txt

Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
---
 arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 54 ++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index 91ea3509..b5f42f5 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -767,6 +767,60 @@ void rdtgroup_exit(struct task_struct *tsk)
 
 static struct rdtgroup *rdtgroup_kn_lock_live(struct kernfs_node *kn);
 static void rdtgroup_kn_unlock(struct kernfs_node *kn);
+static int rdtgroup_cpus_show(struct seq_file *s, void *v)
+{
+	struct kernfs_open_file *of = s->private;
+	struct rdtgroup *rdtgrp;
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+	seq_printf(s, "%*pb\n", cpumask_pr_args(&rdtgrp->cpu_mask));
+	rdtgroup_kn_unlock(of->kn);
+
+	return 0;
+}
+
+static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of,
+			char *buf, size_t nbytes, loff_t off)
+{
+	struct rdtgroup *rdtgrp;
+	unsigned long bitmap[BITS_TO_LONGS(NR_CPUS)];
+	struct cpumask *cpumask;
+	int cpu;
+	struct list_head *l;
+	struct rdtgroup *r;
+
+	if (!buf)
+		return -EINVAL;
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+	if (!rdtgrp)
+		return -ENODEV;
+
+	if (list_empty(&rdtgroup_lists))
+		goto end;
+
+	__bitmap_parse(buf, strlen(buf), 0, bitmap, nr_cpu_ids);
+
+	cpumask = to_cpumask(bitmap);
+
+	list_for_each(l, &rdtgroup_lists) {
+		r = list_entry(l, struct rdtgroup, rdtgroup_list);
+		if (r == rdtgrp)
+			continue;
+
+		for_each_cpu_and(cpu, &r->cpu_mask, cpumask)
+			cpumask_clear_cpu(cpu, &r->cpu_mask);
+	}
+
+	cpumask_copy(&rdtgrp->cpu_mask, cpumask);
+	for_each_cpu(cpu, cpumask)
+		per_cpu(cpu_rdtgroup, cpu) = rdtgrp;
+
+end:
+	rdtgroup_kn_unlock(of->kn);
+
+	return nbytes;
+}
 
 static struct rftype rdtgroup_partition_base_files[] = {
 	{
-- 
2.5.0