Commit 721255b9 authored by Shanker Donthineni's avatar Shanker Donthineni Committed by Thomas Gleixner
Browse files

genirq: Use a maple tree for interrupt descriptor management 



The current implementation uses a static bitmap for interrupt descriptor
allocation and a radix tree to pointer store the pointer for lookup.

However, the size of the bitmap is constrained by the build time macro
MAX_SPARSE_IRQS, which may not be sufficient to support high-end servers,
particularly those with GICv4.1 hardware, which require a large interrupt
space to cover LPIs and vSGIs.

Replace the bitmap and the radix tree with a maple tree, which not only
stores pointers for lookup, but also provides a mechanism to find free
ranges. That removes the build time hardcoded upper limit.

Signed-off-by: default avatarShanker Donthineni <sdonthineni@nvidia.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230519134902.1495562-4-sdonthineni@nvidia.com
parent 5e630aa8

kernel/irq/internals.h

+1 −1
Original line number Diff line number Diff line
@@ -12,7 +12,7 @@ 
#include <linux/sched/clock.h>



#ifdef CONFIG_SPARSE_IRQ

# define MAX_SPARSE_IRQS	(NR_IRQS + 8196)

# define MAX_SPARSE_IRQS	INT_MAX

#else

# define MAX_SPARSE_IRQS	NR_IRQS

#endif

kernel/irq/irqdesc.c

+32 −25
Original line number Diff line number Diff line
@@ -12,8 +12,7 @@ 
#include <linux/export.h>

#include <linux/interrupt.h>

#include <linux/kernel_stat.h>

#include <linux/radix-tree.h>

#include <linux/bitmap.h>

#include <linux/maple_tree.h>

#include <linux/irqdomain.h>

#include <linux/sysfs.h>
@@ -131,17 +130,39 @@ int nr_irqs = NR_IRQS; 
EXPORT_SYMBOL_GPL(nr_irqs);



static DEFINE_MUTEX(sparse_irq_lock);

static DECLARE_BITMAP(allocated_irqs, MAX_SPARSE_IRQS);

static struct maple_tree sparse_irqs = MTREE_INIT_EXT(sparse_irqs,

					MT_FLAGS_ALLOC_RANGE |

					MT_FLAGS_LOCK_EXTERN |

					MT_FLAGS_USE_RCU,

					sparse_irq_lock);



static int irq_find_free_area(unsigned int from, unsigned int cnt)

{

	return bitmap_find_next_zero_area(allocated_irqs, MAX_SPARSE_IRQS,

					  from, cnt, 0);

	MA_STATE(mas, &sparse_irqs, 0, 0);



	if (mas_empty_area(&mas, from, MAX_SPARSE_IRQS, cnt))

		return -ENOSPC;

	return mas.index;

}



static unsigned int irq_find_at_or_after(unsigned int offset)

{

	return find_next_bit(allocated_irqs, nr_irqs, offset);

	unsigned long index = offset;

	struct irq_desc *desc = mt_find(&sparse_irqs, &index, nr_irqs);



	return desc ? irq_desc_get_irq(desc) : nr_irqs;

}



static void irq_insert_desc(unsigned int irq, struct irq_desc *desc)

{

	MA_STATE(mas, &sparse_irqs, irq, irq);

	WARN_ON(mas_store_gfp(&mas, desc, GFP_KERNEL) != 0);

}



static void delete_irq_desc(unsigned int irq)

{

	MA_STATE(mas, &sparse_irqs, irq, irq);

	mas_erase(&mas);

}



#ifdef CONFIG_SPARSE_IRQ
@@ -355,26 +376,14 @@ static void irq_sysfs_del(struct irq_desc *desc) {} 


#endif /* CONFIG_SYSFS */



static RADIX_TREE(irq_desc_tree, GFP_KERNEL);



static void irq_insert_desc(unsigned int irq, struct irq_desc *desc)

{

	radix_tree_insert(&irq_desc_tree, irq, desc);

}



struct irq_desc *irq_to_desc(unsigned int irq)

{

	return radix_tree_lookup(&irq_desc_tree, irq);

	return mtree_load(&sparse_irqs, irq);

}

#ifdef CONFIG_KVM_BOOK3S_64_HV_MODULE

EXPORT_SYMBOL_GPL(irq_to_desc);

#endif



static void delete_irq_desc(unsigned int irq)

{

	radix_tree_delete(&irq_desc_tree, irq);

}



#ifdef CONFIG_SMP

static void free_masks(struct irq_desc *desc)

{
@@ -517,7 +526,6 @@ static int alloc_descs(unsigned int start, unsigned int cnt, int node, 
		irq_sysfs_add(start + i, desc);

		irq_add_debugfs_entry(start + i, desc);

	}

	bitmap_set(allocated_irqs, start, cnt);

	return start;



err:
@@ -557,7 +565,6 @@ int __init early_irq_init(void) 


	for (i = 0; i < initcnt; i++) {

		desc = alloc_desc(i, node, 0, NULL, NULL);

		set_bit(i, allocated_irqs);

		irq_insert_desc(i, desc);

	}

	return arch_early_irq_init();
@@ -612,6 +619,7 @@ static void free_desc(unsigned int irq) 
	raw_spin_lock_irqsave(&desc->lock, flags);

	desc_set_defaults(irq, desc, irq_desc_get_node(desc), NULL, NULL);

	raw_spin_unlock_irqrestore(&desc->lock, flags);

	delete_irq_desc(irq);

}



static inline int alloc_descs(unsigned int start, unsigned int cnt, int node,
@@ -624,8 +632,8 @@ static inline int alloc_descs(unsigned int start, unsigned int cnt, int node, 
		struct irq_desc *desc = irq_to_desc(start + i);



		desc->owner = owner;

		irq_insert_desc(start + i, desc);

	}

	bitmap_set(allocated_irqs, start, cnt);

	return start;

}
@@ -637,7 +645,7 @@ static int irq_expand_nr_irqs(unsigned int nr) 
void irq_mark_irq(unsigned int irq)

{

	mutex_lock(&sparse_irq_lock);

	bitmap_set(allocated_irqs, irq, 1);

	irq_insert_desc(irq, irq_desc + irq);

	mutex_unlock(&sparse_irq_lock);

}
@@ -781,7 +789,6 @@ void irq_free_descs(unsigned int from, unsigned int cnt) 
	for (i = 0; i < cnt; i++)

		free_desc(from + i);



	bitmap_clear(allocated_irqs, from, cnt);

	mutex_unlock(&sparse_irq_lock);

}

EXPORT_SYMBOL_GPL(irq_free_descs);
@@ -844,7 +851,7 @@ EXPORT_SYMBOL_GPL(__irq_alloc_descs); 
 * irq_get_next_irq - get next allocated irq number

 * @offset:	where to start the search

 *

 * Returns next irq number at or after offset or nr_irqs if none is found.

 * Returns next irq number after offset or nr_irqs if none is found.

 */

unsigned int irq_get_next_irq(unsigned int offset)

{