[PATCH v12 17/25] genirq/matrix: Dynamic bitmap allocation

[Anup Patel]

From: Björn Töpel <bjorn at rivosinc.com>

Some (future) users of the irq matrix allocator, do not know the size
of the matrix bitmaps at compile time.

To avoid wasting memory on unnecessary large bitmaps, size the bitmap
at matrix allocation time.

Signed-off-by: Björn Töpel <bjorn at rivosinc.com>
Signed-off-by: Anup Patel <apatel at ventanamicro.com>
---
 arch/x86/include/asm/hw_irq.h |  2 --
 kernel/irq/matrix.c           | 28 +++++++++++++++++-----------
 2 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
index b02c3cd3c0f6..edebf1020e04 100644
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -16,8 +16,6 @@
 
 #include <asm/irq_vectors.h>
 
-#define IRQ_MATRIX_BITS		NR_VECTORS
-
 #ifndef __ASSEMBLY__
 
 #include <linux/percpu.h>
diff --git a/kernel/irq/matrix.c b/kernel/irq/matrix.c
index 75d0ae490e29..8f222d1cccec 100644
--- a/kernel/irq/matrix.c
+++ b/kernel/irq/matrix.c
@@ -8,8 +8,6 @@
 #include <linux/cpu.h>
 #include <linux/irq.h>
 
-#define IRQ_MATRIX_SIZE	(BITS_TO_LONGS(IRQ_MATRIX_BITS))
-
 struct cpumap {
 	unsigned int		available;
 	unsigned int		allocated;
@@ -17,8 +15,8 @@ struct cpumap {
 	unsigned int		managed_allocated;
 	bool			initialized;
 	bool			online;
-	unsigned long		alloc_map[IRQ_MATRIX_SIZE];
-	unsigned long		managed_map[IRQ_MATRIX_SIZE];
+	unsigned long		*managed_map;
+	unsigned long		alloc_map[];
 };
 
 struct irq_matrix {
@@ -32,8 +30,8 @@ struct irq_matrix {
 	unsigned int		total_allocated;
 	unsigned int		online_maps;
 	struct cpumap __percpu	*maps;
-	unsigned long		scratch_map[IRQ_MATRIX_SIZE];
-	unsigned long		system_map[IRQ_MATRIX_SIZE];
+	unsigned long		*system_map;
+	unsigned long		scratch_map[];
 };
 
 #define CREATE_TRACE_POINTS
@@ -50,24 +48,32 @@ __init struct irq_matrix *irq_alloc_matrix(unsigned int matrix_bits,
 					   unsigned int alloc_start,
 					   unsigned int alloc_end)
 {
+	unsigned int cpu, matrix_size = BITS_TO_LONGS(matrix_bits);
 	struct irq_matrix *m;
 
-	if (matrix_bits > IRQ_MATRIX_BITS)
-		return NULL;
-
-	m = kzalloc(sizeof(*m), GFP_KERNEL);
+	m = kzalloc(struct_size(m, scratch_map, matrix_size * 2), GFP_KERNEL);
 	if (!m)
 		return NULL;
 
+	m->system_map = &m->scratch_map[matrix_size];
+
 	m->matrix_bits = matrix_bits;
 	m->alloc_start = alloc_start;
 	m->alloc_end = alloc_end;
 	m->alloc_size = alloc_end - alloc_start;
-	m->maps = alloc_percpu(*m->maps);
+	m->maps = __alloc_percpu(struct_size(m->maps, alloc_map, matrix_size * 2),
+				 __alignof__(*m->maps));
 	if (!m->maps) {
 		kfree(m);
 		return NULL;
 	}
+
+	for_each_possible_cpu(cpu) {
+		struct cpumap *cm = per_cpu_ptr(m->maps, cpu);
+
+		cm->managed_map = &cm->alloc_map[matrix_size];
+	}
+
 	return m;
 }
 
-- 
2.34.1