[RFC PATCH v2 38/45] arm64: smp: Abstract SGI and LPI operations

[Vladimir Murzin]

SGI and LPI backed IPIs require different setup, enable, disable and
send operations. These differences are currently handled by repeatedly
checking percpu_ipi_descs. As the implementation specific logic grows,
these checks make the common IPI code increasingly difficult to
follow.

Introduce an operations structure for each implementation to
encapsulate the specific of SGI and LPI handling, leaving the common
IPI paths generic.

Signed-off-by: Vladimir Murzin <vladimir.murzin at arm.com>
---
 arch/arm64/kernel/smp.c | 163 +++++++++++++++++++++++++---------------
 1 file changed, 101 insertions(+), 62 deletions(-)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 6e5b673613ca..3dd4bc02caed 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -75,11 +75,18 @@ static DEFINE_PER_CPU_READ_MOSTLY(struct ipi_descs, pcpu_ipi_desc);
 
 #define get_ipi_desc(__cpu, __ipi) (per_cpu_ptr(&pcpu_ipi_desc, __cpu)->descs[__ipi])
 
-static bool percpu_ipi_descs __ro_after_init;
+struct ipi_irq_ops {
+	void (*setup)(int ipi, int ncpus);
+	void (*disable)(int cpu, int ipi);
+	void (*enable)(int cpu, int ipi);
+	void (*send)(const cpumask_t *mask, unsigned int nr);
+};
+
+static const struct ipi_irq_ops *ipi_ops __ro_after_init;
 
 static bool crash_stop;
 
-static void ipi_setup(int cpu);
+static void ipi_enable(int cpu);
 
 #ifdef CONFIG_HOTPLUG_CPU
 static void ipi_teardown(int cpu);
@@ -240,7 +247,7 @@ asmlinkage notrace void secondary_start_kernel(void)
 	 */
 	notify_cpu_starting(cpu);
 
-	ipi_setup(cpu);
+	ipi_enable(cpu);
 
 	numa_add_cpu(cpu);
 
@@ -916,13 +923,7 @@ static void __noreturn ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs
 
 static void arm64_send_ipi(const cpumask_t *mask, unsigned int nr)
 {
-	unsigned int cpu;
-
-	if (!percpu_ipi_descs)
-		__ipi_send_mask(get_ipi_desc(0, nr), mask);
-	else
-		for_each_cpu(cpu, mask)
-			__ipi_send_single(get_ipi_desc(cpu, nr), cpu);
+	ipi_ops->send(mask, nr);
 }
 
 static void arm64_backtrace_ipi(cpumask_t *mask)
@@ -1048,53 +1049,13 @@ static bool ipi_should_be_nmi(enum ipi_msg_type ipi)
 	}
 }
 
-static void ipi_setup(int cpu)
-{
-	int i;
-
-	if (WARN_ON_ONCE(!ipi_irq_base))
-		return;
-
-	for (i = 0; i < nr_ipi; i++) {
-		if (!percpu_ipi_descs) {
-			if (ipi_should_be_nmi(i)) {
-				prepare_percpu_nmi(ipi_irq_base + i);
-				enable_percpu_nmi(ipi_irq_base + i, 0);
-			} else {
-				enable_percpu_irq(ipi_irq_base + i, 0);
-			}
-		} else {
-			enable_irq(irq_desc_get_irq(get_ipi_desc(cpu, i)));
-		}
-	}
-}
-
-#ifdef CONFIG_HOTPLUG_CPU
-static void ipi_teardown(int cpu)
+static void ipi_sgi_setup(int ipi, int ncpus)
 {
-	int i;
+	int err, irq, cpu;
 
-	if (WARN_ON_ONCE(!ipi_irq_base))
+	if (WARN_ON_ONCE(ncpus))
 		return;
 
-	for (i = 0; i < nr_ipi; i++) {
-		if (!percpu_ipi_descs) {
-			if (ipi_should_be_nmi(i)) {
-				disable_percpu_nmi(ipi_irq_base + i);
-				teardown_percpu_nmi(ipi_irq_base + i);
-			} else {
-				disable_percpu_irq(ipi_irq_base + i);
-			}
-		} else {
-			disable_irq(irq_desc_get_irq(get_ipi_desc(cpu, i)));
-		}
-	}
-}
-#endif
-
-static void ipi_setup_sgi(int ipi)
-{
-	int err, irq, cpu;
 
 	irq = ipi_irq_base + ipi;
 
@@ -1112,7 +1073,50 @@ static void ipi_setup_sgi(int ipi)
 	irq_set_status_flags(irq, IRQ_HIDDEN);
 }
 
-static void ipi_setup_lpi(int ipi, int ncpus)
+static void ipi_sgi_enable(int cpu, int ipi)
+{
+	if (ipi_should_be_nmi(ipi)) {
+		prepare_percpu_nmi(ipi_irq_base + ipi);
+		enable_percpu_nmi(ipi_irq_base + ipi, 0);
+	} else {
+		enable_percpu_irq(ipi_irq_base + ipi, 0);
+	}
+}
+
+static void ipi_sgi_disable(int cpu, int ipi)
+{
+	if (ipi_should_be_nmi(ipi)) {
+		disable_percpu_nmi(ipi_irq_base + ipi);
+		teardown_percpu_nmi(ipi_irq_base + ipi);
+	} else {
+		disable_percpu_irq(ipi_irq_base + ipi);
+	}
+}
+
+static void ipi_sgi_send(const cpumask_t *mask, unsigned int nr)
+{
+	__ipi_send_mask(get_ipi_desc(0, nr), mask);
+}
+
+static const struct ipi_irq_ops ipi_sgi_ops = {
+	.disable = ipi_sgi_disable,
+	.enable = ipi_sgi_enable,
+	.setup = ipi_sgi_setup,
+	.send = ipi_sgi_send,
+};
+
+
+static void ipi_lpi_enable(int cpu, int ipi)
+{
+	enable_irq(irq_desc_get_irq(get_ipi_desc(cpu, ipi)));
+}
+
+static void ipi_lpi_disable(int cpu, int ipi)
+{
+	disable_irq(irq_desc_get_irq(get_ipi_desc(cpu, ipi)));
+}
+
+static void ipi_lpi_setup(int ipi, int ncpus)
 {
 	for (int cpu = 0; cpu < ncpus; cpu++) {
 		int err, irq;
@@ -1132,6 +1136,44 @@ static void ipi_setup_lpi(int ipi, int ncpus)
 	}
 }
 
+static void ipi_lpi_send(const cpumask_t *mask, unsigned int nr) {
+	int cpu;
+
+	for_each_cpu(cpu, mask)
+		__ipi_send_single(get_ipi_desc(cpu, nr), cpu);
+}
+
+static const struct ipi_irq_ops ipi_lpi_ops = {
+	.disable = ipi_lpi_disable,
+	.enable = ipi_lpi_enable,
+	.setup = ipi_lpi_setup,
+	.send = ipi_lpi_send,
+};
+
+static void ipi_enable(int cpu)
+{
+	int ipi;
+
+	if (WARN_ON_ONCE(!ipi_irq_base))
+		return;
+
+	for (ipi = 0; ipi < nr_ipi; ipi++)
+		ipi_ops->enable(cpu, ipi);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static void ipi_teardown(int cpu)
+{
+	int ipi;
+
+	if (WARN_ON_ONCE(!ipi_irq_base))
+		return;
+
+	for (ipi = 0; ipi < nr_ipi; ipi++)
+		ipi_ops->disable(cpu, ipi);
+}
+#endif
+
 void __init set_smp_ipi_range_percpu(int ipi_base, int n, int ncpus)
 {
 	int i;
@@ -1139,18 +1181,15 @@ void __init set_smp_ipi_range_percpu(int ipi_base, int n, int ncpus)
 	WARN_ON(n < MAX_IPI);
 	nr_ipi = min(n, MAX_IPI);
 
-	percpu_ipi_descs = !!ncpus;
 	ipi_irq_base = ipi_base;
 
-	for (i = 0; i < nr_ipi; i++) {
-		if (!percpu_ipi_descs)
-			ipi_setup_sgi(i);
-		else
-			ipi_setup_lpi(i, ncpus);
-	}
+	ipi_ops = ncpus ? &ipi_lpi_ops : &ipi_sgi_ops;
+
+	for (i = 0; i < nr_ipi; i++)
+		ipi_ops->setup(i, ncpus);
 
 	/* Setup the boot CPU immediately */
-	ipi_setup(smp_processor_id());
+	ipi_enable(smp_processor_id());
 }
 
 void arch_smp_send_reschedule(int cpu)
-- 
2.34.1