linux-kernel - [PATCH 3/8] x86/intel_rdt/mba: Improvements to handle more RDT resources like MBA

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Date:   Tue, 10 Jan 2017 11:33:03 -0800
From:   Vikas Shivappa <vikas.shivappa@...ux.intel.com>
To:     vikas.shivappa@...el.com, linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, hpa@...or.com, tglx@...utronix.de,
        mingo@...nel.org, peterz@...radead.org, ravi.v.shankar@...el.com,
        tony.luck@...el.com, fenghua.yu@...el.com, h.peter.anvin@...el.com,
        vikas.shivappa@...ux.intel.com
Subject: [PATCH 3/8] x86/intel_rdt/mba: Improvements to handle more RDT resources like MBA

This patch does some changes to get ready to handle more resources like
Memory b/w allocation(MBA).

-Update the control registers only when user changes the controls(cbm for
Cache resources and Mem b/w for memory). Hence not sending IPIs on all
domains when user updates the control vals.
-Introduce next_enabled_resource rather than looping through all
resources while parsing each schemata line. The order of resources
should be anyways the same as the root schemata.
-Return error as soon as we detect a resource not entering all domain
values in schemata rather than waiting till we parse all resources.

Signed-off-by: Vikas Shivappa <vikas.shivappa@...ux.intel.com>
---
 arch/x86/include/asm/intel_rdt.h         | 16 +++++++++++++
 arch/x86/kernel/cpu/intel_rdt_schemata.c | 40 +++++++++++++++++---------------
 2 files changed, 37 insertions(+), 19 deletions(-)

diff --git a/arch/x86/include/asm/intel_rdt.h b/arch/x86/include/asm/intel_rdt.h
index 9f66bf5..e1f8acb 100644
--- a/arch/x86/include/asm/intel_rdt.h
+++ b/arch/x86/include/asm/intel_rdt.h
@@ -156,6 +156,22 @@ enum {
 	     r++)							      \
 		if (r->enabled)
 
+/*
+ * Parameter r must be NULL or pointing to
+ * a valid rdt_resource_all entry.
+ * Points r to the next enabled RDT resource at the end.
+ */
+#define next_enabled_rdt_resource(r)					\
+do {									\
+	if (!r)								\
+		r = rdt_resources_all;					\
+	else								\
+		r++;							\
+	for (; r < rdt_resources_all + RDT_NUM_RESOURCES; r++)		\
+		if (r->enabled)						\
+			break;						\
+} while (0)
+
 /* CPUID.(EAX=10H, ECX=ResID=1).EAX */
 union cpuid_0x10_1_eax {
 	struct {
diff --git a/arch/x86/kernel/cpu/intel_rdt_schemata.c b/arch/x86/kernel/cpu/intel_rdt_schemata.c
index c50f742..054d771 100644
--- a/arch/x86/kernel/cpu/intel_rdt_schemata.c
+++ b/arch/x86/kernel/cpu/intel_rdt_schemata.c
@@ -94,6 +94,10 @@ static int parse_line(char *line, struct rdt_resource *r)
 			return -EINVAL;
 	}
 
+	/* Incorrect number of domains in the line */
+	if (r->num_tmp_ctrl != r->num_domains)
+		return -EINVAL;
+
 	/* Any garbage at the end of the line? */
 	if (line && line[0])
 		return -EINVAL;
@@ -114,9 +118,16 @@ static int update_domains(struct rdt_resource *r, int closid)
 	msr_param.high = msr_param.low + 1;
 	msr_param.res = r;
 
+	/*
+	 * Only update the domains that user has changed.
+	 * There by avoiding unnecessary IPIs.
+	 */
 	list_for_each_entry(d, &r->domains, list) {
-		cpumask_set_cpu(cpumask_any(&d->cpu_mask), cpu_mask);
-		d->ctrl_val[msr_param.low] = r->tmp_ctrl[idx++];
+		if (d->ctrl_val[msr_param.low] != r->tmp_ctrl[idx]) {
+			cpumask_set_cpu(cpumask_any(&d->cpu_mask), cpu_mask);
+			d->ctrl_val[msr_param.low] = r->tmp_ctrl[idx];
+		}
+		idx++;
 	}
 	cpu = get_cpu();
 	/* Update CBM on this cpu if it's in cpu_mask. */
@@ -164,30 +175,21 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
 		r->num_tmp_ctrl = 0;
 	}
 
+	r = NULL;
 	while ((tok = strsep(&buf, "\n")) != NULL) {
 		resname = strsep(&tok, ":");
 		if (!tok) {
 			ret = -EINVAL;
 			goto out;
 		}
-		for_each_enabled_rdt_resource(r) {
-			if (!strcmp(resname, r->name) &&
-			    closid < r->num_closid) {
-				ret = parse_line(tok, r);
-				if (ret)
-					goto out;
-				break;
-			}
-		}
-		if (!r->name) {
-			ret = -EINVAL;
-			goto out;
-		}
-	}
 
-	/* Did the parser find all the masks we need? */
-	for_each_enabled_rdt_resource(r) {
-		if (r->num_tmp_ctrl != r->num_domains) {
+		next_enabled_rdt_resource(r);
+
+		if (!strcmp(resname, r->name)) {
+			ret = parse_line(tok, r);
+			if (ret)
+				goto out;
+		} else {
 			ret = -EINVAL;
 			goto out;
 		}
-- 
1.9.1