linux-kernel - [PATCH 6/7] x86/intel_rdt: Intel haswell CAT enumeration

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Date:	Thu, 12 Mar 2015 16:16:06 -0700
From:	Vikas Shivappa <vikas.shivappa@...ux.intel.com>
To:	vikas.shivappa@...el.com
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org, hpa@...or.com,
	tglx@...utronix.de, mingo@...nel.org, tj@...nel.org,
	peterz@...radead.org, matt.fleming@...el.com, will.auld@...el.com,
	glenn.p.williamson@...el.com, kanaka.d.juvva@...el.com,
	vikas.shivappa@...ux.intel.com
Subject: [PATCH 6/7] x86/intel_rdt: Intel haswell CAT enumeration

CAT(Cache Allocation Technology) on hsw needs to be enumerated
separately. CAT is only supported on certain HSW SKUs.  This patch does
a probe test for hsw CPUs by writing a CLOSid into high 32 bits of
IA32_PQR_MSR and see if the bits stick. The probe test is only done
after confirming that the CPU is HSW.

Signed-off-by: Vikas Shivappa <vikas.shivappa@...ux.intel.com>
---
 arch/x86/kernel/cpu/intel_rdt.c | 42 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
index 0330791..aa78711 100644
--- a/arch/x86/kernel/cpu/intel_rdt.c
+++ b/arch/x86/kernel/cpu/intel_rdt.c
@@ -38,11 +38,53 @@ DEFINE_PER_CPU(unsigned int, x86_cpu_clos);
 #define rdt_for_each_child(pos_css, parent_ir)		\
 	css_for_each_child((pos_css), &(parent_ir)->css)
 
+/*
+ * hsw_probetest() - Have to do probe
+ * test for Intel haswell CPUs as it does not have
+ * CPUID enumeration support for CAT.
+ *
+ * Probes by writing to the high 32 bits(CLOSid)
+ * of the IA32_PQR_MSR and testing if the bits stick.
+ * Then hardcode the max CLOS and max bitmask length on hsw.
+ */
+
+static inline bool hsw_probetest(void)
+{
+	u32 l, h_old, h_new, h_tmp;
+
+	if (rdmsr_safe(MSR_IA32_PQR_ASSOC, &l, &h_old))
+		return false;
+
+	/*
+	 * Default value is always 0 if feature is present.
+	 */
+	h_tmp = h_old ^ 0x1U;
+	if (wrmsr_safe(MSR_IA32_PQR_ASSOC, l, h_tmp) ||
+	    rdmsr_safe(MSR_IA32_PQR_ASSOC, &l, &h_new))
+		return false;
+
+	if (h_tmp != h_new)
+		return false;
+
+	wrmsr_safe(MSR_IA32_PQR_ASSOC, l, h_old);
+
+	boot_cpu_data.x86_cat_closs = 4;
+	boot_cpu_data.x86_cat_cbmlength = 20;
+
+	return true;
+}
+
 static inline bool cat_supported(struct cpuinfo_x86 *c)
 {
 	if (cpu_has(c, X86_FEATURE_CAT_L3))
 		return true;
 
+	/*
+	 * Probe test for Haswell CPUs.
+	 */
+	if (c->x86 == 0x6 && c->x86_model == 0x3f)
+		return hsw_probetest();
+
 	return false;
 }
 
-- 
1.9.1

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