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From:   Frederic Weisbecker <frederic@kernel.org>
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        linux-pm@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Frederic Weisbecker <frederic@kernel.org>
Subject: [PATCH 5/7] cpuidle: Introduce CPUIDLE_FLAG_POLLING_HARD
Date:   Fri, 24 Nov 2023 23:32:24 +0100
Message-ID: <20231124223226.24249-6-frederic@kernel.org>
In-Reply-To: <20231124223226.24249-1-frederic@kernel.org>
References: <20231124223226.24249-1-frederic@kernel.org>
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From: Peter Zijlstra <peterz@infradead.org>

Provide a way to tell the cpuidle core about states polling/monitoring
TIF_NEED_RESCHED on the hardware level, monitor/mwait users being the
only examples in use.

This will allow cpuidle core to manage TIF_NR_POLLING on behalf of all
kinds of TIF_NEED_RESCHED polling states while keeping a necessary
distinction for the governors between software loops polling on
TIF_NEED_RESCHED and hardware monitored writes to thread flags.

[fweisbec: _ Initialize flag from acpi_processor_setup_cstates() instead
             of acpi_processor_setup_lpi_states(), as the latter seem to
             be about arm64...
           _ Rename CPUIDLE_FLAG_NO_IPI to CPUIDLE_FLAG_POLLING_HARD]

Not-yet-signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
 drivers/acpi/processor_idle.c | 3 +++
 drivers/idle/intel_idle.c     | 5 ++++-
 include/linux/cpuidle.h       | 3 ++-
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 3a34a8c425fe..a77a4d4b0dad 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -814,6 +814,9 @@ static int acpi_processor_setup_cstates(struct acpi_processor *pr)
 			if (cx->type != ACPI_STATE_C3)
 				drv->safe_state_index = count;
 		}
+
+		if (cx->entry_method == ACPI_CSTATE_FFH)
+			state->flags |= CPUIDLE_FLAG_POLLING_HARD;
 		/*
 		 * Halt-induced C1 is not good for ->enter_s2idle, because it
 		 * re-enables interrupts on exit.  Moreover, C1 is generally not
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 3e01a6b23e75..bc56624fe0b5 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -1563,7 +1563,8 @@ static void __init intel_idle_init_cstates_acpi(struct cpuidle_driver *drv)
 		if (cx->type > ACPI_STATE_C1)
 			state->target_residency *= 3;
 
-		state->flags = MWAIT2flg(cx->address);
+		state->flags = MWAIT2flg(cx->address) | CPUIDLE_FLAG_POLLING_HARD;
+
 		if (cx->type > ACPI_STATE_C2)
 			state->flags |= CPUIDLE_FLAG_TLB_FLUSHED;
 
@@ -1836,6 +1837,8 @@ static bool __init intel_idle_verify_cstate(unsigned int mwait_hint)
 
 static void state_update_enter_method(struct cpuidle_state *state, int cstate)
 {
+	state->flags |= CPUIDLE_FLAG_POLLING_HARD;
+
 	if (state->flags & CPUIDLE_FLAG_INIT_XSTATE) {
 		/*
 		 * Combining with XSTATE with IBRS or IRQ_ENABLE flags
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index 66b59868622c..873fdf200dc3 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -78,13 +78,14 @@ struct cpuidle_state {
 
 /* Idle State Flags */
 #define CPUIDLE_FLAG_NONE       	(0x00)
-#define CPUIDLE_FLAG_POLLING_SOFT		BIT(0) /* polling state */
+#define CPUIDLE_FLAG_POLLING_SOFT	BIT(0) /* software need_resched() polling state */
 #define CPUIDLE_FLAG_COUPLED		BIT(1) /* state applies to multiple cpus */
 #define CPUIDLE_FLAG_TIMER_STOP 	BIT(2) /* timer is stopped on this state */
 #define CPUIDLE_FLAG_UNUSABLE		BIT(3) /* avoid using this state */
 #define CPUIDLE_FLAG_OFF		BIT(4) /* disable this state by default */
 #define CPUIDLE_FLAG_TLB_FLUSHED	BIT(5) /* idle-state flushes TLBs */
 #define CPUIDLE_FLAG_RCU_IDLE		BIT(6) /* idle-state takes care of RCU */
+#define CPUIDLE_FLAG_POLLING_HARD	BIT(7) /* hardware need_resched() polling state */
 
 struct cpuidle_device_kobj;
 struct cpuidle_state_kobj;
-- 
2.42.1