[PATCH 08/32] Define CONFIG_INTEL_RDT

[Fenghua Yu]

From: Vikas Shivappa <vikas.shivappa@xxxxxxxxxxxxxxx>

CONFIG_INTEL_RDT is defined. The option provides support for resource
allocation which is a sub-feature of Intel Resource Director Technology
(RDT).

Signed-off-by: Vikas Shivappa <vikas.shivappa@xxxxxxxxxxxxxxx>
Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
---
 arch/x86/Kconfig                 | 12 ++++++++++++
 arch/x86/include/asm/intel_rdt.h | 10 +++++++++-
 arch/x86/kernel/cpu/intel_rdt.c  | 12 +++++++-----
 include/linux/sched.h            |  3 ---
 4 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d9a94da..231d44c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -408,6 +408,18 @@ config GOLDFISH
        def_bool y
        depends on X86_GOLDFISH
 
+config INTEL_RDT
+	bool "Intel Resource Director Technology support"
+	depends on X86_64 && CPU_SUP_INTEL
+	help
+	  This option provides support for resource allocation which is a
+	  sub-feature of Intel Resource Director Technology(RDT).
+	  Current implementation supports L3 cache allocation.
+	  Using this feature a user can specify the amount of L3 cache space
+	  into which an application can fill.
+
+	  Say N if unsure.
+
 if X86_32
 config X86_EXTENDED_PLATFORM
 	bool "Support for extended (non-PC) x86 platforms"
diff --git a/arch/x86/include/asm/intel_rdt.h b/arch/x86/include/asm/intel_rdt.h
index afb6da3..6e20314 100644
--- a/arch/x86/include/asm/intel_rdt.h
+++ b/arch/x86/include/asm/intel_rdt.h
@@ -24,8 +24,16 @@ struct clos_cbm_table {
  * on scheduler hot path:
  * - This will stay as no-op unless we are running on an Intel SKU
  * which supports L3 cache allocation.
+ * - When support is present and enabled, does not do any
+ * IA32_PQR_MSR writes until the user starts really using the feature
+ * ie creates a rdtgroup directory and assigns a cache_mask thats
+ * different from the root rdtgroup's cache_mask.
  * - Caches the per cpu CLOSid values and does the MSR write only
- * when a task with a different CLOSid is scheduled in.
+ * when a task with a different CLOSid is scheduled in. That
+ * means the task belongs to a different rdtgroup.
+ * - Closids are allocated so that different rdtgroup directories
+ * with same cache_mask gets the same CLOSid. This minimizes CLOSids
+ * used and reduces MSR write frequency.
  */
 static inline void intel_rdt_sched_in(void)
 {
diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
index ecaf8e6..525390a 100644
--- a/arch/x86/kernel/cpu/intel_rdt.c
+++ b/arch/x86/kernel/cpu/intel_rdt.c
@@ -108,17 +108,19 @@ static inline bool cache_alloc_supported(struct cpuinfo_x86 *c)
 	return false;
 }
 
-
 void __intel_rdt_sched_in(void *dummy)
 {
 	struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
-	u32 closid = current->closid;
 
-	if (closid == state->closid)
+	/*
+	 * Currently closid is always 0. When  user interface is added,
+	 * closid will come from user interface.
+	 */
+	if (state->closid == 0)
 		return;
 
-	wrmsr(MSR_IA32_PQR_ASSOC, state->rmid, closid);
-	state->closid = closid;
+	wrmsr(MSR_IA32_PQR_ASSOC, state->rmid, 0);
+	state->closid = 0;
 }
 
 /*
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6005bba..253538f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1761,9 +1761,6 @@ struct task_struct {
 	/* cg_list protected by css_set_lock and tsk->alloc_lock */
 	struct list_head cg_list;
 #endif
-#ifdef CONFIG_INTEL_RDT
-	u32 closid;
-#endif
 #ifdef CONFIG_FUTEX
 	struct robust_list_head __user *robust_list;
 #ifdef CONFIG_COMPAT
-- 
2.5.0