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Subject[PATCH 24/28] x86/intel_rdt/cqm: Add sched_in support
Date
OS associates an RMID/CLOSid to a task by writing the per CPU
IA32_PQR_ASSOC MSR when a task is scheduled in.

The sched_in code will stay as no-op unless we are running on Intel SKU
which supports either resource control or monitoring and we also enable
them by mounting the resctrl fs. The per cpu CLOSid/RMID values are
cached and the write is performed only when a task with a different
CLOSid/RMID is scheduled in.

Signed-off-by: Vikas Shivappa <vikas.shivappa@linux.intel.com>
---
arch/x86/include/asm/intel_rdt_sched.h | 50 ++++++++++++++++++++--------------
arch/x86/kernel/cpu/intel_rdt.h | 4 ---
2 files changed, 29 insertions(+), 25 deletions(-)

diff --git a/arch/x86/include/asm/intel_rdt_sched.h b/arch/x86/include/asm/intel_rdt_sched.h
index 8c5be01..3badc0a 100644
--- a/arch/x86/include/asm/intel_rdt_sched.h
+++ b/arch/x86/include/asm/intel_rdt_sched.h
@@ -15,7 +15,8 @@
*
* The upper 32 bits of IA32_PQR_ASSOC contain closid and the
* lower 10 bits rmid. The update to IA32_PQR_ASSOC always
- * contains both parts, so we need to cache them.
+ * contains both parts, so we need to cache them. This also
+ * stores the user configured per cpu CLOSID and RMID.
*
* The cache also helps to avoid pointless updates if the value does
* not change.
@@ -30,38 +31,45 @@ struct intel_pqr_state {

DECLARE_STATIC_KEY_FALSE(rdt_enable_key);
DECLARE_STATIC_KEY_FALSE(rdt_alloc_enable_key);
+DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key);

/*
- * __intel_rdt_sched_in() - Writes the task's CLOSid to IA32_PQR_MSR
+ * __intel_rdt_sched_in() - Writes the task's CLOSid/RMID to IA32_PQR_MSR
*
* Following considerations are made so that this has minimal impact
* on scheduler hot path:
* - This will stay as no-op unless we are running on an Intel SKU
- * which supports resource control and we enable by mounting the
- * resctrl file system.
- * - Caches the per cpu CLOSid values and does the MSR write only
- * when a task with a different CLOSid is scheduled in.
- *
+ * which supports resource control or monitoring and we enable by
+ * mounting the resctrl file system.
+ * - Caches the per cpu CLOSid/RMID values and does the MSR write only
+ * when a task with a different CLOSid/RMID is scheduled in.
+ * - We allocate RMIDs/CLOSids globally in order to keep this as
+ * simple as possible.
* Must be called with preemption disabled.
*/
-static inline void __intel_rdt_sched_in(void)
+static void __intel_rdt_sched_in(void)
{
+ struct intel_pqr_state newstate = this_cpu_read(rdt_cpu_default);
+ struct intel_pqr_state *curstate = this_cpu_ptr(&pqr_state);
+
+ /*
+ * If this task has a closid/rmid assigned, use it.
+ * Else use the closid/rmid assigned to this cpu.
+ */
if (static_branch_likely(&rdt_alloc_enable_key)) {
- struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
- u32 closid;
+ if (current->closid)
+ newstate.closid = current->closid;
+ }

- /*
- * If this task has a closid assigned, use it.
- * Else use the closid assigned to this cpu.
- */
- closid = current->closid;
- if (closid == 0)
- closid = this_cpu_read(rdt_cpu_default.closid);
+ if (static_branch_likely(&rdt_mon_enable_key)) {
+ if (current->rmid)
+ newstate.rmid = current->rmid;
+ }

- if (closid != state->closid) {
- state->closid = closid;
- wrmsr(IA32_PQR_ASSOC, state->rmid, closid);
- }
+ if (newstate.closid != curstate->closid ||
+ newstate.rmid != curstate->rmid) {
+ *curstate = newstate;
+ wrmsr(IA32_PQR_ASSOC, newstate.rmid, newstate.closid);
}
}

diff --git a/arch/x86/kernel/cpu/intel_rdt.h b/arch/x86/kernel/cpu/intel_rdt.h
index 92a5d30..7fcaa5f 100644
--- a/arch/x86/kernel/cpu/intel_rdt.h
+++ b/arch/x86/kernel/cpu/intel_rdt.h
@@ -22,8 +22,6 @@
#define RMID_VAL_ERROR BIT_ULL(63)
#define RMID_VAL_UNAVAIL BIT_ULL(62)

-DECLARE_STATIC_KEY_FALSE(rdt_enable_key);
-
/**
* struct mon_evt - Entry in the event list of a resource
* @evtid: event id
@@ -61,8 +59,6 @@ struct rmid_read {
extern bool rdt_mon_capable;
extern unsigned int rdt_mon_features;

-DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key);
-
enum rdt_group_type {
RDTCTRL_GROUP = 0,
RDTMON_GROUP,
--
1.9.1
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