linux-kernel - [PATCH v2 28/33] x86/intel_rdt_rdtgroup.c: Read and write cpus

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Date:   Thu,  8 Sep 2016 02:57:22 -0700
From:   "Fenghua Yu" <fenghua.yu@...el.com>
To:     "Thomas Gleixner" <tglx@...utronix.de>,
        "H. Peter Anvin" <h.peter.anvin@...el.com>,
        "Ingo Molnar" <mingo@...e.hu>, "Tony Luck" <tony.luck@...el.com>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "Tejun Heo" <tj@...nel.org>, "Borislav Petkov" <bp@...e.de>,
        "Stephane Eranian" <eranian@...gle.com>,
        "Marcelo Tosatti" <mtosatti@...hat.com>,
        "David Carrillo-Cisneros" <davidcc@...gle.com>,
        "Shaohua Li" <shli@...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 v2 28/33] 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 | 92 ++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)

diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index 71231ba..6c3161a 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -59,6 +59,10 @@ static struct dentry *rdt_mount(struct file_system_type *fs_type,
 			 void *data);
 static void rdt_kill_sb(struct super_block *sb);
 
+static int rdtgroup_cpus_show(struct seq_file *s, void *v);
+static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of,
+			char *buf, size_t nbytes, loff_t off);
+
 /* rdtgroup core interface files */
 static struct rftype rdtgroup_root_base_files[] = {
 	{
@@ -1189,3 +1193,91 @@ static void rdt_kill_sb(struct super_block *sb)
 
 	mutex_unlock(&rdtgroup_mutex);
 }
+
+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);
+	if (!rdtgrp)
+		return -ENODEV;
+
+	seq_printf(s, "%*pb\n", cpumask_pr_args(&rdtgrp->cpu_mask));
+	rdtgroup_kn_unlock(of->kn);
+
+	return 0;
+}
+
+static int cpus_validate(struct cpumask *cpumask, struct rdtgroup *rdtgrp)
+{
+	int old_cpumask_bit, new_cpumask_bit;
+	int cpu;
+
+	for_each_online_cpu(cpu) {
+		old_cpumask_bit = cpumask_test_cpu(cpu, &rdtgrp->cpu_mask);
+		new_cpumask_bit = cpumask_test_cpu(cpu, cpumask);
+		/* Cannot clear a "cpus" bit in a rdtgroup. */
+		if (old_cpumask_bit == 1 && new_cpumask_bit == 0)
+			return -EINVAL;
+	}
+
+	/* If a cpu is not online, cannot set it. */
+	for_each_cpu(cpu, cpumask) {
+		if (!cpu_online(cpu))
+			return -EINVAL;
+	}
+
+	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;
+	int ret = 0;
+
+	if (!buf)
+		return -EINVAL;
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+	if (!rdtgrp)
+		return -ENODEV;
+
+	if (list_empty(&rdtgroup_lists)) {
+		ret = -EINVAL;
+		goto end;
+	}
+
+	ret = __bitmap_parse(buf, strlen(buf), 0, bitmap, nr_cpu_ids);
+	if (ret)
+		goto end;
+
+	cpumask = to_cpumask(bitmap);
+	ret = cpus_validate(cpumask, rdtgrp);
+	if (ret)
+		goto end;
+
+	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 ret ?: nbytes;
+}
-- 
2.5.0