linux-kernel - [PATCH 8/8] x86/intel_rdt/mba: Add schemata file support for MBA

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Date:   Mon,  3 Apr 2017 14:57:32 -0700
From:   Vikas Shivappa <vikas.shivappa@...ux.intel.com>
To:     vikas.shivappa@...el.com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     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
Subject: [PATCH 8/8] x86/intel_rdt/mba: Add schemata file support for MBA

Add support to update the MBA bandwidth values for the domains. The MBA
bandwidth values are specified by updating the schemata.

We do the following to parse the bandwidth(bw) value from
schemata and update the PQOS_MSRS:

  1. check the bw to satisfy the minimum and max bandwidth requirements.

  2. To meet the granularity requirement intermediate values are rounded
     to the next control step available on the hardware.

  3. map the bw to delay values and write the delay values to
     corresponding domain PQOS_MSRs which are indexed from 0xD50. For
     linear scale the delay value = 100 - bw. Currently no Intel SKUs
     support non-linear delay values.

Signed-off-by: Vikas Shivappa <vikas.shivappa@...ux.intel.com>
---
 arch/x86/include/asm/intel_rdt.h         |  1 +
 arch/x86/kernel/cpu/intel_rdt.c          |  2 ++
 arch/x86/kernel/cpu/intel_rdt_schemata.c | 46 ++++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/arch/x86/include/asm/intel_rdt.h b/arch/x86/include/asm/intel_rdt.h
index 6fc82a3..7a77fec 100644
--- a/arch/x86/include/asm/intel_rdt.h
+++ b/arch/x86/include/asm/intel_rdt.h
@@ -162,6 +162,7 @@ struct rdt_resource {
 void rdt_get_cache_infofile(struct rdt_resource *r);
 void rdt_get_mba_infofile(struct rdt_resource *r);
 int parse_cbm(char *buf, struct rdt_resource *r, struct rdt_domain *d);
+int parse_bw(char *buf, struct rdt_resource *r,  struct rdt_domain *d);
 
 extern struct mutex rdtgroup_mutex;
 
diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
index 2c18142..34bcfbc 100644
--- a/arch/x86/kernel/cpu/intel_rdt.c
+++ b/arch/x86/kernel/cpu/intel_rdt.c
@@ -106,7 +106,9 @@ struct rdt_resource rdt_resources_all[] = {
 		.name		= "MB",
 		.domains	= domain_init(RDT_RESOURCE_MBA),
 		.msr_base	= IA32_MBA_THRTL_BASE,
+		.parse_ctrlval	= parse_bw,
 		.msr_update	= mba_wrmsr,
+		.format_str	= "%d=%*d",
 		.cache_level	= 3,
 		.cbm_idx_multi	= 1,
 		.cbm_idx_offset = 0
diff --git a/arch/x86/kernel/cpu/intel_rdt_schemata.c b/arch/x86/kernel/cpu/intel_rdt_schemata.c
index 03f9a70..9154695 100644
--- a/arch/x86/kernel/cpu/intel_rdt_schemata.c
+++ b/arch/x86/kernel/cpu/intel_rdt_schemata.c
@@ -29,6 +29,52 @@
 #include <asm/intel_rdt.h>
 
 /*
+ * Check whether MBA bandwidth percentage value is correct.
+ * The value is checked against the minimum  and max bandwidth
+ * values specified by the hardware. The allocated b/w
+ * percentage is rounded off the next control step
+ * available on the hardware.
+ */
+static bool bw_validate(char *buf, unsigned long *data, struct rdt_resource *r)
+{
+	unsigned long bw, m;
+	int ret;
+
+	/*
+	 * Only linear delay values is supported for current Intel SKUs.
+	 */
+	if (!r->delay_linear)
+		return false;
+
+	ret = kstrtoul(buf, 10, &bw);
+	if (ret)
+		return false;
+
+	if (bw < r->min_bw || bw > r->default_ctrl)
+		return false;
+
+	m = (bw + r->bw_gran - 1) / r->bw_gran;
+	*data = m * r->bw_gran;
+
+	return true;
+}
+
+int parse_bw(char *buf, struct rdt_resource *r, struct rdt_domain *d)
+{
+	unsigned long data;
+
+	if (d->have_new_ctrl)
+		return -EINVAL;
+
+	if (!bw_validate(buf, &data, r))
+		return -EINVAL;
+	d->new_ctrl = data;
+	d->have_new_ctrl = true;
+
+	return 0;
+}
+
+/*
  * Check whether a cache bit mask is valid. The SDM says:
  *	Please note that all (and only) contiguous '1' combinations
  *	are allowed (e.g. FFFFH, 0FF0H, 003CH, etc.).
-- 
1.9.1