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Subject[PATCH] x86/intel_rdt: Implement "update" mode when writing schemata file
Date
From: Tony Luck <tony.luck@intel.com>

The schemata file can have multiple lines and it is cumbersome to
update from shell scripts.

Remove code that requires that the user provide values for every
resource (in the right order). If the user provides values for
just a few resources, update them and leave the rest unchanged.

Side benefit: we now check which values were updated and only send
IPIs to cpus that actually have updates.

Cc: Vikas Shivappa <vikas.shivappa@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Tested-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
---
Documentation/x86/intel_rdt_ui.txt | 14 ++++++
arch/x86/include/asm/intel_rdt.h | 10 ++---
arch/x86/kernel/cpu/intel_rdt.c | 2 -
arch/x86/kernel/cpu/intel_rdt_schemata.c | 73 +++++++++++++-------------------
4 files changed, 48 insertions(+), 51 deletions(-)

diff --git a/Documentation/x86/intel_rdt_ui.txt b/Documentation/x86/intel_rdt_ui.txt
index 51cf6fa5591f..3ea198460469 100644
--- a/Documentation/x86/intel_rdt_ui.txt
+++ b/Documentation/x86/intel_rdt_ui.txt
@@ -129,6 +129,20 @@ schemata format is always:

L2:<cache_id0>=<cbm>;<cache_id1>=<cbm>;...

+Reading/writing the schemata file
+---------------------------------
+Reading the schemata file will show the state of all resources
+on all domains. When writing you only need to specify those values
+which you wish to change. E.g.
+
+# cat schemata
+L3DATA:0=fffff;1=fffff;2=fffff;3=fffff
+L3CODE:0=fffff;1=fffff;2=fffff;3=fffff
+# echo "L3DATA:2=3c0;" > schemata
+# cat schemata
+L3DATA:0=fffff;1=fffff;2=3c0;3=fffff
+L3CODE:0=fffff;1=fffff;2=fffff;3=fffff
+
Example 1
---------
On a two socket machine (one L3 cache per socket) with just four bits
diff --git a/arch/x86/include/asm/intel_rdt.h b/arch/x86/include/asm/intel_rdt.h
index 0d64397cee58..d7705270c401 100644
--- a/arch/x86/include/asm/intel_rdt.h
+++ b/arch/x86/include/asm/intel_rdt.h
@@ -76,10 +76,7 @@ struct rftype {
* @min_cbm_bits: Minimum number of consecutive bits to be set
* in a cache bit mask
* @domains: All domains for this resource
- * @num_domains: Number of domains active
* @msr_base: Base MSR address for CBMs
- * @tmp_cbms: Scratch space when updating schemata
- * @num_tmp_cbms: Number of CBMs in tmp_cbms
* @cache_level: Which cache level defines scope of this domain
* @cbm_idx_multi: Multiplier of CBM index
* @cbm_idx_offset: Offset of CBM index. CBM index is computed by:
@@ -94,10 +91,7 @@ struct rdt_resource {
int min_cbm_bits;
u32 max_cbm;
struct list_head domains;
- int num_domains;
int msr_base;
- u32 *tmp_cbms;
- int num_tmp_cbms;
int cache_level;
int cbm_idx_multi;
int cbm_idx_offset;
@@ -109,12 +103,16 @@ struct rdt_resource {
* @id: unique id for this instance
* @cpu_mask: which cpus share this resource
* @cbm: array of cache bit masks (indexed by CLOSID)
+ * @new_cbm: new cbm value to be loaded
+ * @have_new_cbm: did user provide new_cbm for this domain
*/
struct rdt_domain {
struct list_head list;
int id;
struct cpumask cpu_mask;
u32 *cbm;
+ u32 new_cbm;
+ bool have_new_cbm;
};

/**
diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
index 5a533fefefa0..329b8876b984 100644
--- a/arch/x86/kernel/cpu/intel_rdt.c
+++ b/arch/x86/kernel/cpu/intel_rdt.c
@@ -309,7 +309,6 @@ static void domain_add_cpu(int cpu, struct rdt_resource *r)

cpumask_set_cpu(cpu, &d->cpu_mask);
list_add_tail(&d->list, add_pos);
- r->num_domains++;
}

static void domain_remove_cpu(int cpu, struct rdt_resource *r)
@@ -325,7 +324,6 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r)

cpumask_clear_cpu(cpu, &d->cpu_mask);
if (cpumask_empty(&d->cpu_mask)) {
- r->num_domains--;
kfree(d->cbm);
list_del(&d->list);
kfree(d);
diff --git a/arch/x86/kernel/cpu/intel_rdt_schemata.c b/arch/x86/kernel/cpu/intel_rdt_schemata.c
index f369cb8db0d5..c8e054f4f269 100644
--- a/arch/x86/kernel/cpu/intel_rdt_schemata.c
+++ b/arch/x86/kernel/cpu/intel_rdt_schemata.c
@@ -56,7 +56,7 @@ static bool cbm_validate(unsigned long var, struct rdt_resource *r)
* Read one cache bit mask (hex). Check that it is valid for the current
* resource type.
*/
-static int parse_cbm(char *buf, struct rdt_resource *r)
+static int parse_cbm(char *buf, struct rdt_resource *r, struct rdt_domain *d)
{
unsigned long data;
int ret;
@@ -66,7 +66,8 @@ static int parse_cbm(char *buf, struct rdt_resource *r)
return ret;
if (!cbm_validate(data, r))
return -EINVAL;
- r->tmp_cbms[r->num_tmp_cbms++] = data;
+ d->new_cbm = data;
+ d->have_new_cbm = true;

return 0;
}
@@ -74,8 +75,8 @@ static int parse_cbm(char *buf, struct rdt_resource *r)
/*
* For each domain in this resource we expect to find a series of:
* id=mask
- * separated by ";". The "id" is in decimal, and must appear in the
- * right order.
+ * separated by ";". The "id" is in decimal, and must match one of
+ * the "id"s for this resource.
*/
static int parse_line(char *line, struct rdt_resource *r)
{
@@ -83,21 +84,21 @@ static int parse_line(char *line, struct rdt_resource *r)
struct rdt_domain *d;
unsigned long dom_id;

+next:
+ if (!line || line[0] == '\0')
+ return 0;
+ dom = strsep(&line, ";");
+ id = strsep(&dom, "=");
+ if (!dom || kstrtoul(id, 10, &dom_id))
+ return -EINVAL;
list_for_each_entry(d, &r->domains, list) {
- dom = strsep(&line, ";");
- if (!dom)
- return -EINVAL;
- id = strsep(&dom, "=");
- if (kstrtoul(id, 10, &dom_id) || dom_id != d->id)
- return -EINVAL;
- if (parse_cbm(dom, r))
- return -EINVAL;
+ if (d->id == dom_id) {
+ if (parse_cbm(dom, r, d))
+ return -EINVAL;
+ goto next;
+ }
}
-
- /* Any garbage at the end of the line? */
- if (line && line[0])
- return -EINVAL;
- return 0;
+ return -EINVAL;
}

static int update_domains(struct rdt_resource *r, int closid)
@@ -105,7 +106,7 @@ static int update_domains(struct rdt_resource *r, int closid)
struct msr_param msr_param;
cpumask_var_t cpu_mask;
struct rdt_domain *d;
- int cpu, idx = 0;
+ int cpu;

if (!zalloc_cpumask_var(&cpu_mask, GFP_KERNEL))
return -ENOMEM;
@@ -115,9 +116,13 @@ static int update_domains(struct rdt_resource *r, int closid)
msr_param.res = r;

list_for_each_entry(d, &r->domains, list) {
- cpumask_set_cpu(cpumask_any(&d->cpu_mask), cpu_mask);
- d->cbm[msr_param.low] = r->tmp_cbms[idx++];
+ if (d->have_new_cbm && d->new_cbm != d->cbm[closid]) {
+ cpumask_set_cpu(cpumask_any(&d->cpu_mask), cpu_mask);
+ d->cbm[closid] = d->new_cbm;
+ }
}
+ if (cpumask_empty(cpu_mask))
+ goto done;
cpu = get_cpu();
/* Update CBM on this cpu if it's in cpu_mask. */
if (cpumask_test_cpu(cpu, cpu_mask))
@@ -126,6 +131,7 @@ static int update_domains(struct rdt_resource *r, int closid)
smp_call_function_many(cpu_mask, rdt_cbm_update, &msr_param, 1);
put_cpu();

+done:
free_cpumask_var(cpu_mask);

return 0;
@@ -135,10 +141,10 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
struct rdtgroup *rdtgrp;
+ struct rdt_domain *dom;
struct rdt_resource *r;
char *tok, *resname;
int closid, ret = 0;
- u32 *l3_cbms = NULL;

/* Valid input requires a trailing newline */
if (nbytes == 0 || buf[nbytes - 1] != '\n')
@@ -153,16 +159,9 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,

closid = rdtgrp->closid;

- /* get scratch space to save all the masks while we validate input */
- for_each_enabled_rdt_resource(r) {
- r->tmp_cbms = kcalloc(r->num_domains, sizeof(*l3_cbms),
- GFP_KERNEL);
- if (!r->tmp_cbms) {
- ret = -ENOMEM;
- goto out;
- }
- r->num_tmp_cbms = 0;
- }
+ for_each_enabled_rdt_resource(r)
+ list_for_each_entry(dom, &r->domains, list)
+ dom->have_new_cbm = false;

while ((tok = strsep(&buf, "\n")) != NULL) {
resname = strsep(&tok, ":");
@@ -185,14 +184,6 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
}
}

- /* Did the parser find all the masks we need? */
- for_each_enabled_rdt_resource(r) {
- if (r->num_tmp_cbms != r->num_domains) {
- ret = -EINVAL;
- goto out;
- }
- }
-
for_each_enabled_rdt_resource(r) {
ret = update_domains(r, closid);
if (ret)
@@ -201,10 +192,6 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,

out:
rdtgroup_kn_unlock(of->kn);
- for_each_enabled_rdt_resource(r) {
- kfree(r->tmp_cbms);
- r->tmp_cbms = NULL;
- }
return ret ?: nbytes;
}

--
2.7.4
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