linux-kernel - [PATCH 5.7 296/376] irqchip/sifive-plic: Setup cpuhp once after boot CPU handler is present

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Message-Id: <20200619141724.352736298@linuxfoundation.org>
Date:   Fri, 19 Jun 2020 16:33:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Anup Patel <anup.patel@....com>,
        Marc Zyngier <maz@...nel.org>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>
Subject: [PATCH 5.7 296/376] irqchip/sifive-plic: Setup cpuhp once after boot CPU handler is present

From: Anup Patel <anup.patel@....com>

commit 2234ae846ccb9ebdf4c391824cb79e73674dceda upstream.

For multiple PLIC instances, the plic_init() is called once for each
PLIC instance. Due to this we have two issues:
1. cpuhp_setup_state() is called multiple times
2. plic_starting_cpu() can crash for boot CPU if cpuhp_setup_state()
   is called before boot CPU PLIC handler is available.

Address both issues by only initializing the HP notifiers when
the boot CPU setup is complete.

Fixes: f1ad1133b18f ("irqchip/sifive-plic: Add support for multiple PLICs")
Signed-off-by: Anup Patel <anup.patel@....com>
Signed-off-by: Marc Zyngier <maz@...nel.org>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
Acked-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/r/20200518091441.94843-3-anup.patel@wdc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/irqchip/irq-sifive-plic.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -76,6 +76,7 @@ struct plic_handler {
 	void __iomem		*enable_base;
 	struct plic_priv	*priv;
 };
+static bool plic_cpuhp_setup_done;
 static DEFINE_PER_CPU(struct plic_handler, plic_handlers);
 
 static inline void plic_toggle(struct plic_handler *handler,
@@ -285,6 +286,7 @@ static int __init plic_init(struct devic
 	int error = 0, nr_contexts, nr_handlers = 0, i;
 	u32 nr_irqs;
 	struct plic_priv *priv;
+	struct plic_handler *handler;
 
 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 	if (!priv)
@@ -315,7 +317,6 @@ static int __init plic_init(struct devic
 
 	for (i = 0; i < nr_contexts; i++) {
 		struct of_phandle_args parent;
-		struct plic_handler *handler;
 		irq_hw_number_t hwirq;
 		int cpu, hartid;
 
@@ -369,9 +370,18 @@ done:
 		nr_handlers++;
 	}
 
-	cpuhp_setup_state(CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
+	/*
+	 * We can have multiple PLIC instances so setup cpuhp state only
+	 * when context handler for current/boot CPU is present.
+	 */
+	handler = this_cpu_ptr(&plic_handlers);
+	if (handler->present && !plic_cpuhp_setup_done) {
+		cpuhp_setup_state(CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
 				  "irqchip/sifive/plic:starting",
 				  plic_starting_cpu, plic_dying_cpu);
+		plic_cpuhp_setup_done = true;
+	}
+
 	pr_info("mapped %d interrupts with %d handlers for %d contexts.\n",
 		nr_irqs, nr_handlers, nr_contexts);
 	set_handle_irq(plic_handle_irq);