[PATCH v4 13/28] x86, irq: Add alloc_reserved_irq_and_cfg_at()

[Yinghai Lu <yinghai@xxxxxxxxxx>]

For ioapic hot-add support, it would be easy if we have continuous
irq numbers for new added ioapic controller.

We can reserve irq range at first, then allocate those
pre-reserved one when it is needed.

Add alloc_reserved_irq_and_cfg_at() to really allocate irq_desc and cfg,
because pre-reserved only mark bits in allocate_irqs bit maps.

Also fallback to alloc_irq_and_cfg_at(), and it is needed as
we do not actually reserved irq for io apic irq yet.

This patch is x86 arch code.

-v2: update changelog by adding reasons, requested by Konrad.
-v3: according to tglx, separate to another patch, and use
     alloc_reserved_... instead of realloc_...
     also add handling for one possible path in
       alloc_reserved_irq_and_cfg_at().

Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <sebastian@xxxxxxxxxxxxx>
---
 arch/x86/kernel/apic/io_apic.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index ef2d530..c883da9 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -301,6 +301,29 @@ static void free_irq_at(unsigned int at, struct irq_cfg *cfg)
 	irq_free_desc(at);
 }
 
+static struct irq_cfg *alloc_reserved_irq_and_cfg_at(unsigned int at, int node)
+{
+	struct irq_cfg *cfg;
+	int res;
+
+	res = irq_alloc_reserved_desc_at(at, node);
+
+	if (res >= 0) {
+		cfg = irq_desc_get_chip_data(irq_to_desc(at));
+		if (cfg)
+			return cfg;
+
+		cfg = alloc_irq_cfg(at, node);
+		if (cfg)
+			irq_set_chip_data(at, cfg);
+		else
+			irq_free_desc(at);
+
+		return cfg;
+	}
+
+	return alloc_irq_and_cfg_at(at, node);
+}
 
 struct io_apic {
 	unsigned int index;
@@ -3352,7 +3375,7 @@ int arch_setup_ht_irq(unsigned int irq, struct pci_dev *dev)
 static int
 io_apic_setup_irq_pin(unsigned int irq, int node, struct io_apic_irq_attr *attr)
 {
-	struct irq_cfg *cfg = alloc_irq_and_cfg_at(irq, node);
+	struct irq_cfg *cfg = alloc_reserved_irq_and_cfg_at(irq, node);
 	int ret;
 
 	if (!cfg)
-- 
1.8.1.4

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