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Subject[PATCH v4 14/18] x86/intel_rdt: Add cpus file
Date
From: Tony Luck <tony.luck@intel.com>

Now we populate each directory with a read/write (mode 0644) file
named "cpus". This is used to over-ride the resources available
to processes in the default resource group when running on specific
CPUs. Each "cpus" file reads as a cpumask showing which CPUs belong
to this resource group. Initially all online CPUs are assigned to
the default group. They can be added to other groups by writing a
cpumask to the "cpus" file in the directory for the resource group
(which will remove them from the previous group to which they were
assigned). CPU online/offline operations will delete CPUs that go
offline from whatever group they are in and add new CPUs to the
default group.

If there are CPUs assigned to a group when the directory is removed,
they are returned to the default group.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
---
arch/x86/include/asm/intel_rdt.h | 5 ++
arch/x86/kernel/cpu/intel_rdt.c | 12 +++
arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 127 +++++++++++++++++++++++++++++++
3 files changed, 144 insertions(+)

diff --git a/arch/x86/include/asm/intel_rdt.h b/arch/x86/include/asm/intel_rdt.h
index 7eb8078..6ab31ba 100644
--- a/arch/x86/include/asm/intel_rdt.h
+++ b/arch/x86/include/asm/intel_rdt.h
@@ -9,13 +9,16 @@
* @kn: kernfs node
* @rdtgroup_list: linked list for all rdtgroups
* @closid: closid for this rdtgroup
+ * @cpu_mask: CPUs assigned to this rdtgroup
* @flags: status bits
* @waitcount: how many cpus expect to find this
+ * group when they acquire rdtgroup_mutex
*/
struct rdtgroup {
struct kernfs_node *kn;
struct list_head rdtgroup_list;
int closid;
+ struct cpumask cpu_mask;
int flags;
atomic_t waitcount;
};
@@ -148,6 +151,8 @@ union cpuid_0x10_1_edx {
unsigned int full;
};

+DECLARE_PER_CPU_READ_MOSTLY(int, cpu_closid);
+
void rdt_cbm_update(void *arg);
struct rdtgroup *rdtgroup_kn_lock_live(struct kernfs_node *kn);
void rdtgroup_kn_unlock(struct kernfs_node *kn);
diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
index 3d4a125..556a426 100644
--- a/arch/x86/kernel/cpu/intel_rdt.c
+++ b/arch/x86/kernel/cpu/intel_rdt.c
@@ -36,6 +36,8 @@
/* Mutex to protect rdtgroup access. */
DEFINE_MUTEX(rdtgroup_mutex);

+DEFINE_PER_CPU_READ_MOSTLY(int, cpu_closid);
+
#define domain_init(name) LIST_HEAD_INIT(rdt_resources_all[name].domains)

struct rdt_resource rdt_resources_all[] = {
@@ -242,8 +244,11 @@ static int intel_rdt_online_cpu(unsigned int cpu)
struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);

mutex_lock(&rdtgroup_mutex);
+ per_cpu(cpu_closid, cpu) = 0;
for_each_rdt_resource(r)
update_domain(cpu, r, 1);
+ /* The cpu is set in default rdtgroup after online. */
+ cpumask_set_cpu(cpu, &rdtgroup_default.cpu_mask);
state->closid = 0;
wrmsr(MSR_IA32_PQR_ASSOC, state->rmid, 0);
mutex_unlock(&rdtgroup_mutex);
@@ -254,10 +259,17 @@ static int intel_rdt_online_cpu(unsigned int cpu)
static int intel_rdt_offline_cpu(unsigned int cpu)
{
struct rdt_resource *r;
+ struct rdtgroup *rdtgrp;
+ struct list_head *l;

mutex_lock(&rdtgroup_mutex);
for_each_rdt_resource(r)
update_domain(cpu, r, 0);
+ list_for_each(l, &rdt_all_groups) {
+ rdtgrp = list_entry(l, struct rdtgroup, rdtgroup_list);
+ if (cpumask_test_and_clear_cpu(cpu, &rdtgrp->cpu_mask))
+ break;
+ }
mutex_unlock(&rdtgroup_mutex);

return 0;
diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index 9e0044d..f2d7a3a 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -20,6 +20,7 @@

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

+#include <linux/cpu.h>
#include <linux/fs.h>
#include <linux/sysfs.h>
#include <linux/kernfs.h>
@@ -180,6 +181,117 @@ static struct kernfs_ops rdtgroup_kf_single_ops = {
.seq_show = rdtgroup_seqfile_show,
};

+static int rdtgroup_cpus_show(struct kernfs_open_file *of,
+ struct seq_file *s, void *v)
+{
+ struct rdtgroup *rdtgrp;
+ int ret = 0;
+
+ rdtgrp = rdtgroup_kn_lock_live(of->kn);
+
+ if (rdtgrp)
+ seq_printf(s, "%*pb\n", cpumask_pr_args(&rdtgrp->cpu_mask));
+ else
+ ret = -ENOENT;
+ rdtgroup_kn_unlock(of->kn);
+
+ return ret;
+}
+
+static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ struct rdtgroup *rdtgrp, *r;
+ cpumask_var_t tmpmask, newmask;
+ int ret, cpu;
+
+ if (!buf)
+ return -EINVAL;
+
+ if (!alloc_cpumask_var(&tmpmask, GFP_KERNEL))
+ return -ENOMEM;
+ if (!alloc_cpumask_var(&newmask, GFP_KERNEL)) {
+ free_cpumask_var(tmpmask);
+ return -ENOMEM;
+ }
+ rdtgrp = rdtgroup_kn_lock_live(of->kn);
+ if (!rdtgrp) {
+ ret = -ENOENT;
+ goto unlock;
+ }
+
+ ret = cpumask_parse(buf, newmask);
+ if (ret)
+ goto unlock;
+
+ get_online_cpus();
+ /* check that user didn't specify any offline cpus */
+ cpumask_andnot(tmpmask, newmask, cpu_online_mask);
+ if (cpumask_weight(tmpmask)) {
+ ret = -EINVAL;
+ goto end;
+ }
+
+ /* Are trying to drop some cpus from this group? */
+ cpumask_andnot(tmpmask, &rdtgrp->cpu_mask, newmask);
+ if (cpumask_weight(tmpmask)) {
+ /* Can't drop from default group */
+ if (rdtgrp == &rdtgroup_default) {
+ ret = -EINVAL;
+ goto end;
+ }
+ /* 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;
+ }
+
+ /*
+ * If we added cpus, remove them from previous group that owned them
+ * and update per-cpu rdtgroup pointers to refer to us
+ */
+ cpumask_andnot(tmpmask, newmask, &rdtgrp->cpu_mask);
+ if (cpumask_weight(tmpmask)) {
+ struct list_head *l;
+
+ list_for_each(l, &rdt_all_groups) {
+ r = list_entry(l, struct rdtgroup, rdtgroup_list);
+ if (r == rdtgrp)
+ continue;
+ cpumask_andnot(&r->cpu_mask, &r->cpu_mask, tmpmask);
+ }
+ for_each_cpu(cpu, tmpmask)
+ per_cpu(cpu_closid, cpu) = rdtgrp->closid;
+ }
+
+ /* Done pushing/pulling - update this group with new mask */
+ cpumask_copy(&rdtgrp->cpu_mask, newmask);
+
+end:
+ put_online_cpus();
+unlock:
+ rdtgroup_kn_unlock(of->kn);
+ free_cpumask_var(tmpmask);
+ free_cpumask_var(newmask);
+
+ return ret ?: nbytes;
+}
+
+/* Files in each rdtgroup */
+static struct rftype rdtgroup_base_files[] = {
+ {
+ .name = "cpus",
+ .mode = 0644,
+ .kf_ops = &rdtgroup_kf_single_ops,
+ .write = rdtgroup_cpus_write,
+ .seq_show = rdtgroup_cpus_show,
+ },
+ {
+ /* NULL terminated */
+ }
+};
+
static int rdt_num_closid_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
@@ -545,6 +657,10 @@ static int rdtgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
if (ret)
goto out_destroy;

+ ret = rdtgroup_add_files(kn, rdtgroup_base_files);
+ if (ret)
+ goto out_destroy;
+
kernfs_activate(kn);

ret = 0;
@@ -582,6 +698,10 @@ static int rdtgroup_rmdir(struct kernfs_node *kn)
return -EPERM;
}

+ /* Give any CPUs back to the default group */
+ cpumask_or(&rdtgroup_default.cpu_mask,
+ &rdtgroup_default.cpu_mask, &rdtgrp->cpu_mask);
+
rdtgrp->flags = RDT_DELETED;
closid_free(rdtgrp->closid);
list_del(&rdtgrp->rdtgroup_list);
@@ -618,11 +738,18 @@ static int __init rdtgroup_setup_root(void)
rdtgroup_default.closid = 0;
list_add(&rdtgroup_default.rdtgroup_list, &rdt_all_groups);

+ ret = rdtgroup_add_files(rdt_root->kn, rdtgroup_base_files);
+ if (ret) {
+ kernfs_destroy_root(rdt_root);
+ goto out;
+ }
+
rdtgroup_default.kn = rdt_root->kn;
ret = rdtgroup_create_info_dir(rdtgroup_default.kn);
if (!ret)
kernfs_activate(rdtgroup_default.kn);

+out:
mutex_unlock(&rdtgroup_mutex);

return 0;
--
2.5.0
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