kernel/irq/affinity.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2016 Thomas Gleixner.
  * Copyright (C) 2016-2017 Christoph Hellwig.
  */
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/cpu.h>
 #include <linux/sort.h>

 static void irq_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
 				unsigned int cpus_per_vec)
 {
 	const struct cpumask *siblmsk;
 	int cpu, sibl;

 	for ( ; cpus_per_vec > 0; ) {
 		cpu = cpumask_first(nmsk);

 		/* Should not happen, but I'm too lazy to think about it */
 		if (cpu >= nr_cpu_ids)
 			return;

 		cpumask_clear_cpu(cpu, nmsk);
 		cpumask_set_cpu(cpu, irqmsk);
 		cpus_per_vec--;

 		/* If the cpu has siblings, use them first */
 		siblmsk = topology_sibling_cpumask(cpu);
 		for (sibl = -1; cpus_per_vec > 0; ) {
 			sibl = cpumask_next(sibl, siblmsk);
 			if (sibl >= nr_cpu_ids)
 				break;
 			if (!cpumask_test_and_clear_cpu(sibl, nmsk))
 				continue;
 			cpumask_set_cpu(sibl, irqmsk);
 			cpus_per_vec--;
 		}
 	}
 }

 static cpumask_var_t *alloc_node_to_cpumask(void)
 {
 	cpumask_var_t *masks;
 	int node;

 	masks = kcalloc(nr_node_ids, sizeof(cpumask_var_t), GFP_KERNEL);
 	if (!masks)
 		return NULL;

 	for (node = 0; node < nr_node_ids; node++) {
 		if (!zalloc_cpumask_var(&masks[node], GFP_KERNEL))
 			goto out_unwind;
 	}

 	return masks;

 out_unwind:
 	while (--node >= 0)
 		free_cpumask_var(masks[node]);
 	kfree(masks);
 	return NULL;
 }

 static void free_node_to_cpumask(cpumask_var_t *masks)
 {
 	int node;

 	for (node = 0; node < nr_node_ids; node++)
 		free_cpumask_var(masks[node]);
 	kfree(masks);
 }

 static void build_node_to_cpumask(cpumask_var_t *masks)
 {
 	int cpu;

 	for_each_possible_cpu(cpu)
 		cpumask_set_cpu(cpu, masks[cpu_to_node(cpu)]);
 }

 static int get_nodes_in_cpumask(cpumask_var_t *node_to_cpumask,
 				const struct cpumask *mask, nodemask_t *nodemsk)
 {
 	int n, nodes = 0;

 	/* Calculate the number of nodes in the supplied affinity mask */
 	for_each_node(n) {
 		if (cpumask_intersects(mask, node_to_cpumask[n])) {
 			node_set(n, *nodemsk);
 			nodes++;
 		}
 	}
 	return nodes;
 }

 struct node_vectors {
 	unsigned id;

 	union {
 		unsigned nvectors;
 		unsigned ncpus;
 	};
 };

 static int ncpus_cmp_func(const void *l, const void *r)
 {
 	const struct node_vectors *ln = l;
 	const struct node_vectors *rn = r;

 	return ln->ncpus - rn->ncpus;
 }

 /*
  * Allocate vector number for each node, so that for each node:
  *
  * 1) the allocated number is >= 1
  *
  * 2) the allocated numbver is <= active CPU number of this node
  *
  * The actual allocated total vectors may be less than @numvecs when
  * active total CPU number is less than @numvecs.
  *
  * Active CPUs means the CPUs in '@cpu_mask AND @node_to_cpumask[]'
  * for each node.
  */
 static void alloc_nodes_vectors(unsigned int numvecs,
 				cpumask_var_t *node_to_cpumask,
 				const struct cpumask *cpu_mask,
 				const nodemask_t nodemsk,
 				struct cpumask *nmsk,
 				struct node_vectors *node_vectors)
 {
 	unsigned n, remaining_ncpus = 0;

 	for (n = 0; n < nr_node_ids; n++) {
 		node_vectors[n].id = n;
 		node_vectors[n].ncpus = UINT_MAX;
 	}

 	for_each_node_mask(n, nodemsk) {
 		unsigned ncpus;

 		cpumask_and(nmsk, cpu_mask, node_to_cpumask[n]);
 		ncpus = cpumask_weight(nmsk);

 		if (!ncpus)
 			continue;
 		remaining_ncpus += ncpus;
 		node_vectors[n].ncpus = ncpus;
 	}

 	numvecs = min_t(unsigned, remaining_ncpus, numvecs);

 	sort(node_vectors, nr_node_ids, sizeof(node_vectors[0]),
 	     ncpus_cmp_func, NULL);

 	/*
 	 * Allocate vectors for each node according to the ratio of this
 	 * node's nr_cpus to remaining un-assigned ncpus. 'numvecs' is
 	 * bigger than number of active numa nodes. Always start the
 	 * allocation from the node with minimized nr_cpus.
 	 *
 	 * This way guarantees that each active node gets allocated at
 	 * least one vector, and the theory is simple: over-allocation
 	 * is only done when this node is assigned by one vector, so
 	 * other nodes will be allocated >= 1 vector, since 'numvecs' is
 	 * bigger than number of numa nodes.
 	 *
 	 * One perfect invariant is that number of allocated vectors for
 	 * each node is <= CPU count of this node:
 	 *
 	 * 1) suppose there are two nodes: A and B
 	 * 	ncpu(X) is CPU count of node X
 	 * 	vecs(X) is the vector count allocated to node X via this
 	 * 	algorithm
 	 *
 	 * 	ncpu(A) <= ncpu(B)
 	 * 	ncpu(A) + ncpu(B) = N
 	 * 	vecs(A) + vecs(B) = V
 	 *
 	 * 	vecs(A) = max(1, round_down(V * ncpu(A) / N))
 	 * 	vecs(B) = V - vecs(A)
 	 *
 	 * 	both N and V are integer, and 2 <= V <= N, suppose
 	 * 	V = N - delta, and 0 <= delta <= N - 2
 	 *
 	 * 2) obviously vecs(A) <= ncpu(A) because:
 	 *
 	 * 	if vecs(A) is 1, then vecs(A) <= ncpu(A) given
 	 * 	ncpu(A) >= 1
 	 *
 	 * 	otherwise,
 	 * 		vecs(A) <= V * ncpu(A) / N <= ncpu(A), given V <= N
 	 *
 	 * 3) prove how vecs(B) <= ncpu(B):
 	 *
 	 * 	if round_down(V * ncpu(A) / N) == 0, vecs(B) won't be
 	 * 	over-allocated, so vecs(B) <= ncpu(B),
 	 *
 	 * 	otherwise:
 	 *
 	 * 	vecs(A) =
 	 * 		round_down(V * ncpu(A) / N) =
 	 * 		round_down((N - delta) * ncpu(A) / N) =
 	 * 		round_down((N * ncpu(A) - delta * ncpu(A)) / N)	 >=
 	 * 		round_down((N * ncpu(A) - delta * N) / N)	 =
 	 * 		cpu(A) - delta
 	 *
 	 * 	then:
 	 *
 	 * 	vecs(A) - V >= ncpu(A) - delta - V
 	 * 	=>
 	 * 	V - vecs(A) <= V + delta - ncpu(A)
 	 * 	=>
 	 * 	vecs(B) <= N - ncpu(A)
 	 * 	=>
 	 * 	vecs(B) <= cpu(B)
 	 *
 	 * For nodes >= 3, it can be thought as one node and another big
 	 * node given that is exactly what this algorithm is implemented,
 	 * and we always re-calculate 'remaining_ncpus' & 'numvecs', and
 	 * finally for each node X: vecs(X) <= ncpu(X).
 	 *
 	 */
 	for (n = 0; n < nr_node_ids; n++) {
 		unsigned nvectors, ncpus;

 		if (node_vectors[n].ncpus == UINT_MAX)
 			continue;

 		WARN_ON_ONCE(numvecs == 0);

 		ncpus = node_vectors[n].ncpus;
 		nvectors = max_t(unsigned, 1,
 				 numvecs * ncpus / remaining_ncpus);
 		WARN_ON_ONCE(nvectors > ncpus);

 		node_vectors[n].nvectors = nvectors;

 		remaining_ncpus -= ncpus;
 		numvecs -= nvectors;
 	}
 }

 static int __irq_build_affinity_masks(unsigned int startvec,
 				      unsigned int numvecs,
 				      unsigned int firstvec,
 				      cpumask_var_t *node_to_cpumask,
 				      const struct cpumask *cpu_mask,
 				      struct cpumask *nmsk,
 				      struct irq_affinity_desc *masks)
 {
 	unsigned int i, n, nodes, cpus_per_vec, extra_vecs, done = 0;
 	unsigned int last_affv = firstvec + numvecs;
 	unsigned int curvec = startvec;
 	nodemask_t nodemsk = NODE_MASK_NONE;
 	struct node_vectors *node_vectors;

 	if (!cpumask_weight(cpu_mask))
 		return 0;

 	nodes = get_nodes_in_cpumask(node_to_cpumask, cpu_mask, &nodemsk);

 	/*
 	 * If the number of nodes in the mask is greater than or equal the
 	 * number of vectors we just spread the vectors across the nodes.
 	 */
 	if (numvecs <= nodes) {
 		for_each_node_mask(n, nodemsk) {
 			cpumask_or(&masks[curvec].mask, &masks[curvec].mask,
 				   node_to_cpumask[n]);
 			if (++curvec == last_affv)
 				curvec = firstvec;
 		}
 		return numvecs;
 	}

 	node_vectors = kcalloc(nr_node_ids,
 			       sizeof(struct node_vectors),
 			       GFP_KERNEL);
 	if (!node_vectors)
 		return -ENOMEM;

 	/* allocate vector number for each node */
 	alloc_nodes_vectors(numvecs, node_to_cpumask, cpu_mask,
 			    nodemsk, nmsk, node_vectors);

 	for (i = 0; i < nr_node_ids; i++) {
 		unsigned int ncpus, v;
 		struct node_vectors *nv = &node_vectors[i];

 		if (nv->nvectors == UINT_MAX)
 			continue;

 		/* Get the cpus on this node which are in the mask */
 		cpumask_and(nmsk, cpu_mask, node_to_cpumask[nv->id]);
 		ncpus = cpumask_weight(nmsk);
 		if (!ncpus)
 			continue;

 		WARN_ON_ONCE(nv->nvectors > ncpus);

 		/* Account for rounding errors */
 		extra_vecs = ncpus - nv->nvectors * (ncpus / nv->nvectors);

 		/* Spread allocated vectors on CPUs of the current node */
 		for (v = 0; v < nv->nvectors; v++, curvec++) {
 			cpus_per_vec = ncpus / nv->nvectors;

 			/* Account for extra vectors to compensate rounding errors */
 			if (extra_vecs) {
 				cpus_per_vec++;
 				--extra_vecs;
 			}

 			/*
 			 * wrapping has to be considered given 'startvec'
 			 * may start anywhere
 			 */
 			if (curvec >= last_affv)
 				curvec = firstvec;
 			irq_spread_init_one(&masks[curvec].mask, nmsk,
 						cpus_per_vec);
 		}
 		done += nv->nvectors;
 	}
 	kfree(node_vectors);
 	return done;
 }

 /*
  * build affinity in two stages:
  *	1) spread present CPU on these vectors
  *	2) spread other possible CPUs on these vectors
  */
 static int irq_build_affinity_masks(unsigned int startvec, unsigned int numvecs,
 				    unsigned int firstvec,
 				    struct irq_affinity_desc *masks)
 {
 	unsigned int curvec = startvec, nr_present = 0, nr_others = 0;
 	cpumask_var_t *node_to_cpumask;
 	cpumask_var_t nmsk, npresmsk;
 	int ret = -ENOMEM;

 	if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL))
 		return ret;

 	if (!zalloc_cpumask_var(&npresmsk, GFP_KERNEL))
 		goto fail_nmsk;

 	node_to_cpumask = alloc_node_to_cpumask();
 	if (!node_to_cpumask)
 		goto fail_npresmsk;

 	/* Stabilize the cpumasks */
 	get_online_cpus();
 	build_node_to_cpumask(node_to_cpumask);

 	/* Spread on present CPUs starting from affd->pre_vectors */
 	ret = __irq_build_affinity_masks(curvec, numvecs, firstvec,
 					 node_to_cpumask, cpu_present_mask,
 					 nmsk, masks);
 	if (ret < 0)
 		goto fail_build_affinity;
 	nr_present = ret;

 	/*
 	 * Spread on non present CPUs starting from the next vector to be
 	 * handled. If the spreading of present CPUs already exhausted the
 	 * vector space, assign the non present CPUs to the already spread
 	 * out vectors.
 	 */
 	if (nr_present >= numvecs)
 		curvec = firstvec;
 	else
 		curvec = firstvec + nr_present;
 	cpumask_andnot(npresmsk, cpu_possible_mask, cpu_present_mask);
 	ret = __irq_build_affinity_masks(curvec, numvecs, firstvec,
 					 node_to_cpumask, npresmsk, nmsk,
 					 masks);
 	if (ret >= 0)
 		nr_others = ret;

  fail_build_affinity:
 	put_online_cpus();

 	if (ret >= 0)
 		WARN_ON(nr_present + nr_others < numvecs);

 	free_node_to_cpumask(node_to_cpumask);

  fail_npresmsk:
 	free_cpumask_var(npresmsk);

  fail_nmsk:
 	free_cpumask_var(nmsk);
 	return ret < 0 ? ret : 0;
 }

 static void default_calc_sets(struct irq_affinity *affd, unsigned int affvecs)
 {
 	affd->nr_sets = 1;
 	affd->set_size[0] = affvecs;
 }

 /**
  * irq_create_affinity_masks - Create affinity masks for multiqueue spreading
  * @nvecs:	The total number of vectors
  * @affd:	Description of the affinity requirements
  *
  * Returns the irq_affinity_desc pointer or NULL if allocation failed.
  */
 struct irq_affinity_desc *
 irq_create_affinity_masks(unsigned int nvecs, struct irq_affinity *affd)
 {
 	unsigned int affvecs, curvec, usedvecs, i;
 	struct irq_affinity_desc *masks = NULL;

 	/*
 	 * Determine the number of vectors which need interrupt affinities
 	 * assigned. If the pre/post request exhausts the available vectors
 	 * then nothing to do here except for invoking the calc_sets()
 	 * callback so the device driver can adjust to the situation.
 	 */
 	if (nvecs > affd->pre_vectors + affd->post_vectors)
 		affvecs = nvecs - affd->pre_vectors - affd->post_vectors;
 	else
 		affvecs = 0;

 	/*
 	 * Simple invocations do not provide a calc_sets() callback. Install
 	 * the generic one.
 	 */
 	if (!affd->calc_sets)
 		affd->calc_sets = default_calc_sets;

 	/* Recalculate the sets */
 	affd->calc_sets(affd, affvecs);

 	if (WARN_ON_ONCE(affd->nr_sets > IRQ_AFFINITY_MAX_SETS))
 		return NULL;

 	/* Nothing to assign? */
 	if (!affvecs)
 		return NULL;

 	masks = kcalloc(nvecs, sizeof(*masks), GFP_KERNEL);
 	if (!masks)
 		return NULL;

 	/* Fill out vectors at the beginning that don't need affinity */
 	for (curvec = 0; curvec < affd->pre_vectors; curvec++)
 		cpumask_copy(&masks[curvec].mask, irq_default_affinity);

 	/*
 	 * Spread on present CPUs starting from affd->pre_vectors. If we
 	 * have multiple sets, build each sets affinity mask separately.
 	 */
 	for (i = 0, usedvecs = 0; i < affd->nr_sets; i++) {
 		unsigned int this_vecs = affd->set_size[i];
 		int ret;

 		ret = irq_build_affinity_masks(curvec, this_vecs,
 					       curvec, masks);
 		if (ret) {
 			kfree(masks);
 			return NULL;
 		}
 		curvec += this_vecs;
 		usedvecs += this_vecs;
 	}

 	/* Fill out vectors at the end that don't need affinity */
 	if (usedvecs >= affvecs)
 		curvec = affd->pre_vectors + affvecs;
 	else
 		curvec = affd->pre_vectors + usedvecs;
 	for (; curvec < nvecs; curvec++)
 		cpumask_copy(&masks[curvec].mask, irq_default_affinity);

 	/* Mark the managed interrupts */
 	for (i = affd->pre_vectors; i < nvecs - affd->post_vectors; i++)
 		masks[i].is_managed = 1;

 	return masks;
 }

 /**
  * irq_calc_affinity_vectors - Calculate the optimal number of vectors
  * @minvec:	The minimum number of vectors available
  * @maxvec:	The maximum number of vectors available
  * @affd:	Description of the affinity requirements
  */
 unsigned int irq_calc_affinity_vectors(unsigned int minvec, unsigned int maxvec,
 				       const struct irq_affinity *affd)
 {
 	unsigned int resv = affd->pre_vectors + affd->post_vectors;
 	unsigned int set_vecs;

 	if (resv > minvec)
 		return 0;

 	if (affd->calc_sets) {
 		set_vecs = maxvec - resv;
 	} else {
 		get_online_cpus();
 		set_vecs = cpumask_weight(cpu_possible_mask);
 		put_online_cpus();
 	}

 	return resv + min(set_vecs, maxvec - resv);
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright (C) 2016 Thomas Gleixner.
	* Copyright (C) 2016-2017 Christoph Hellwig.
	*/
	#include <linux/interrupt.h>
	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/cpu.h>
	#include <linux/sort.h>

	static void irq_spread_init_one(struct cpumask irqmsk, struct cpumask nmsk,
	unsigned int cpus_per_vec)
	{
	const struct cpumask *siblmsk;
	int cpu, sibl;

	for ( ; cpus_per_vec > 0; ) {
	cpu = cpumask_first(nmsk);

	/* Should not happen, but I'm too lazy to think about it */
	if (cpu >= nr_cpu_ids)
	return;

	cpumask_clear_cpu(cpu, nmsk);
	cpumask_set_cpu(cpu, irqmsk);
	cpus_per_vec--;

	/* If the cpu has siblings, use them first */
	siblmsk = topology_sibling_cpumask(cpu);
	for (sibl = -1; cpus_per_vec > 0; ) {
	sibl = cpumask_next(sibl, siblmsk);
	if (sibl >= nr_cpu_ids)
	break;
	if (!cpumask_test_and_clear_cpu(sibl, nmsk))
	continue;
	cpumask_set_cpu(sibl, irqmsk);
	cpus_per_vec--;
	}
	}
	}

	static cpumask_var_t *alloc_node_to_cpumask(void)
	{
	cpumask_var_t *masks;
	int node;

	masks = kcalloc(nr_node_ids, sizeof(cpumask_var_t), GFP_KERNEL);
	if (!masks)
	return NULL;

	for (node = 0; node < nr_node_ids; node++) {
	if (!zalloc_cpumask_var(&masks[node], GFP_KERNEL))
	goto out_unwind;
	}

	return masks;

	out_unwind:
	while (--node >= 0)
	free_cpumask_var(masks[node]);
	kfree(masks);
	return NULL;
	}

	static void free_node_to_cpumask(cpumask_var_t *masks)
	{
	int node;

	for (node = 0; node < nr_node_ids; node++)
	free_cpumask_var(masks[node]);
	kfree(masks);
	}

	static void build_node_to_cpumask(cpumask_var_t *masks)
	{
	int cpu;

	for_each_possible_cpu(cpu)
	cpumask_set_cpu(cpu, masks[cpu_to_node(cpu)]);
	}

	static int get_nodes_in_cpumask(cpumask_var_t *node_to_cpumask,
	const struct cpumask mask, nodemask_t nodemsk)
	{
	int n, nodes = 0;

	/* Calculate the number of nodes in the supplied affinity mask */
	for_each_node(n) {
	if (cpumask_intersects(mask, node_to_cpumask[n])) {
	node_set(n, *nodemsk);
	nodes++;
	}
	}
	return nodes;
	}

	struct node_vectors {
	unsigned id;

	union {
	unsigned nvectors;
	unsigned ncpus;
	};
	};

	static int ncpus_cmp_func(const void l, const void r)
	{
	const struct node_vectors *ln = l;
	const struct node_vectors *rn = r;

	return ln->ncpus - rn->ncpus;
	}

	/*
	* Allocate vector number for each node, so that for each node:
	*
	* 1) the allocated number is >= 1
	*
	* 2) the allocated numbver is <= active CPU number of this node
	*
	* The actual allocated total vectors may be less than @numvecs when
	* active total CPU number is less than @numvecs.
	*
	* Active CPUs means the CPUs in '@cpu_mask AND @node_to_cpumask[]'
	* for each node.
	*/
	static void alloc_nodes_vectors(unsigned int numvecs,
	cpumask_var_t *node_to_cpumask,
	const struct cpumask *cpu_mask,
	const nodemask_t nodemsk,
	struct cpumask *nmsk,
	struct node_vectors *node_vectors)
	{
	unsigned n, remaining_ncpus = 0;

	for (n = 0; n < nr_node_ids; n++) {
	node_vectors[n].id = n;
	node_vectors[n].ncpus = UINT_MAX;
	}

	for_each_node_mask(n, nodemsk) {
	unsigned ncpus;

	cpumask_and(nmsk, cpu_mask, node_to_cpumask[n]);
	ncpus = cpumask_weight(nmsk);

	if (!ncpus)
	continue;
	remaining_ncpus += ncpus;
	node_vectors[n].ncpus = ncpus;
	}

	numvecs = min_t(unsigned, remaining_ncpus, numvecs);

	sort(node_vectors, nr_node_ids, sizeof(node_vectors[0]),
	ncpus_cmp_func, NULL);

	/*
	* Allocate vectors for each node according to the ratio of this
	* node's nr_cpus to remaining un-assigned ncpus. 'numvecs' is
	* bigger than number of active numa nodes. Always start the
	* allocation from the node with minimized nr_cpus.
	*
	* This way guarantees that each active node gets allocated at
	* least one vector, and the theory is simple: over-allocation
	* is only done when this node is assigned by one vector, so
	* other nodes will be allocated >= 1 vector, since 'numvecs' is
	* bigger than number of numa nodes.
	*
	* One perfect invariant is that number of allocated vectors for
	* each node is <= CPU count of this node:
	*
	* 1) suppose there are two nodes: A and B
	* ncpu(X) is CPU count of node X
	* vecs(X) is the vector count allocated to node X via this
	* algorithm
	*
	* ncpu(A) <= ncpu(B)
	* ncpu(A) + ncpu(B) = N
	* vecs(A) + vecs(B) = V
	*
	* vecs(A) = max(1, round_down(V * ncpu(A) / N))
	* vecs(B) = V - vecs(A)
	*
	* both N and V are integer, and 2 <= V <= N, suppose
	* V = N - delta, and 0 <= delta <= N - 2
	*
	* 2) obviously vecs(A) <= ncpu(A) because:
	*
	* if vecs(A) is 1, then vecs(A) <= ncpu(A) given
	* ncpu(A) >= 1
	*
	* otherwise,
	* vecs(A) <= V * ncpu(A) / N <= ncpu(A), given V <= N
	*
	* 3) prove how vecs(B) <= ncpu(B):
	*
	* if round_down(V * ncpu(A) / N) == 0, vecs(B) won't be
	* over-allocated, so vecs(B) <= ncpu(B),
	*
	* otherwise:
	*
	* vecs(A) =
	* round_down(V * ncpu(A) / N) =
	* round_down((N - delta) * ncpu(A) / N) =
	* round_down((N * ncpu(A) - delta * ncpu(A)) / N) >=
	* round_down((N * ncpu(A) - delta * N) / N) =
	* cpu(A) - delta
	*
	* then:
	*
	* vecs(A) - V >= ncpu(A) - delta - V
	* =>
	* V - vecs(A) <= V + delta - ncpu(A)
	* =>
	* vecs(B) <= N - ncpu(A)
	* =>
	* vecs(B) <= cpu(B)
	*
	* For nodes >= 3, it can be thought as one node and another big
	* node given that is exactly what this algorithm is implemented,
	* and we always re-calculate 'remaining_ncpus' & 'numvecs', and
	* finally for each node X: vecs(X) <= ncpu(X).
	*
	*/
	for (n = 0; n < nr_node_ids; n++) {
	unsigned nvectors, ncpus;

	if (node_vectors[n].ncpus == UINT_MAX)
	continue;

	WARN_ON_ONCE(numvecs == 0);

	ncpus = node_vectors[n].ncpus;
	nvectors = max_t(unsigned, 1,
	numvecs * ncpus / remaining_ncpus);
	WARN_ON_ONCE(nvectors > ncpus);

	node_vectors[n].nvectors = nvectors;

	remaining_ncpus -= ncpus;
	numvecs -= nvectors;
	}
	}

	static int __irq_build_affinity_masks(unsigned int startvec,
	unsigned int numvecs,
	unsigned int firstvec,
	cpumask_var_t *node_to_cpumask,
	const struct cpumask *cpu_mask,
	struct cpumask *nmsk,
	struct irq_affinity_desc *masks)
	{
	unsigned int i, n, nodes, cpus_per_vec, extra_vecs, done = 0;
	unsigned int last_affv = firstvec + numvecs;
	unsigned int curvec = startvec;
	nodemask_t nodemsk = NODE_MASK_NONE;
	struct node_vectors *node_vectors;

	if (!cpumask_weight(cpu_mask))
	return 0;

	nodes = get_nodes_in_cpumask(node_to_cpumask, cpu_mask, &nodemsk);

	/*
	* If the number of nodes in the mask is greater than or equal the
	* number of vectors we just spread the vectors across the nodes.
	*/
	if (numvecs <= nodes) {
	for_each_node_mask(n, nodemsk) {
	cpumask_or(&masks[curvec].mask, &masks[curvec].mask,
	node_to_cpumask[n]);
	if (++curvec == last_affv)
	curvec = firstvec;
	}
	return numvecs;
	}

	node_vectors = kcalloc(nr_node_ids,
	sizeof(struct node_vectors),
	GFP_KERNEL);
	if (!node_vectors)
	return -ENOMEM;

	/* allocate vector number for each node */
	alloc_nodes_vectors(numvecs, node_to_cpumask, cpu_mask,
	nodemsk, nmsk, node_vectors);

	for (i = 0; i < nr_node_ids; i++) {
	unsigned int ncpus, v;
	struct node_vectors *nv = &node_vectors[i];

	if (nv->nvectors == UINT_MAX)
	continue;

	/* Get the cpus on this node which are in the mask */
	cpumask_and(nmsk, cpu_mask, node_to_cpumask[nv->id]);
	ncpus = cpumask_weight(nmsk);
	if (!ncpus)
	continue;

	WARN_ON_ONCE(nv->nvectors > ncpus);

	/* Account for rounding errors */
	extra_vecs = ncpus - nv->nvectors * (ncpus / nv->nvectors);

	/* Spread allocated vectors on CPUs of the current node */
	for (v = 0; v < nv->nvectors; v++, curvec++) {
	cpus_per_vec = ncpus / nv->nvectors;

	/* Account for extra vectors to compensate rounding errors */
	if (extra_vecs) {
	cpus_per_vec++;
	--extra_vecs;
	}

	/*
	* wrapping has to be considered given 'startvec'
	* may start anywhere
	*/
	if (curvec >= last_affv)
	curvec = firstvec;
	irq_spread_init_one(&masks[curvec].mask, nmsk,
	cpus_per_vec);
	}
	done += nv->nvectors;
	}
	kfree(node_vectors);
	return done;
	}

	/*
	* build affinity in two stages:
	* 1) spread present CPU on these vectors
	* 2) spread other possible CPUs on these vectors
	*/
	static int irq_build_affinity_masks(unsigned int startvec, unsigned int numvecs,
	unsigned int firstvec,
	struct irq_affinity_desc *masks)
	{
	unsigned int curvec = startvec, nr_present = 0, nr_others = 0;
	cpumask_var_t *node_to_cpumask;
	cpumask_var_t nmsk, npresmsk;
	int ret = -ENOMEM;

	if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL))
	return ret;

	if (!zalloc_cpumask_var(&npresmsk, GFP_KERNEL))
	goto fail_nmsk;

	node_to_cpumask = alloc_node_to_cpumask();
	if (!node_to_cpumask)
	goto fail_npresmsk;

	/* Stabilize the cpumasks */
	get_online_cpus();
	build_node_to_cpumask(node_to_cpumask);

	/* Spread on present CPUs starting from affd->pre_vectors */
	ret = __irq_build_affinity_masks(curvec, numvecs, firstvec,
	node_to_cpumask, cpu_present_mask,
	nmsk, masks);
	if (ret < 0)
	goto fail_build_affinity;
	nr_present = ret;

	/*
	* Spread on non present CPUs starting from the next vector to be
	* handled. If the spreading of present CPUs already exhausted the
	* vector space, assign the non present CPUs to the already spread
	* out vectors.
	*/
	if (nr_present >= numvecs)
	curvec = firstvec;
	else
	curvec = firstvec + nr_present;
	cpumask_andnot(npresmsk, cpu_possible_mask, cpu_present_mask);
	ret = __irq_build_affinity_masks(curvec, numvecs, firstvec,
	node_to_cpumask, npresmsk, nmsk,
	masks);
	if (ret >= 0)
	nr_others = ret;

	fail_build_affinity:
	put_online_cpus();

	if (ret >= 0)
	WARN_ON(nr_present + nr_others < numvecs);

	free_node_to_cpumask(node_to_cpumask);

	fail_npresmsk:
	free_cpumask_var(npresmsk);

	fail_nmsk:
	free_cpumask_var(nmsk);
	return ret < 0 ? ret : 0;
	}

	static void default_calc_sets(struct irq_affinity *affd, unsigned int affvecs)
	{
	affd->nr_sets = 1;
	affd->set_size[0] = affvecs;
	}

	/**
	* irq_create_affinity_masks - Create affinity masks for multiqueue spreading
	* @nvecs: The total number of vectors
	* @affd: Description of the affinity requirements
	*
	* Returns the irq_affinity_desc pointer or NULL if allocation failed.
	*/
	struct irq_affinity_desc *
	irq_create_affinity_masks(unsigned int nvecs, struct irq_affinity *affd)
	{
	unsigned int affvecs, curvec, usedvecs, i;
	struct irq_affinity_desc *masks = NULL;

	/*
	* Determine the number of vectors which need interrupt affinities
	* assigned. If the pre/post request exhausts the available vectors
	* then nothing to do here except for invoking the calc_sets()
	* callback so the device driver can adjust to the situation.
	*/
	if (nvecs > affd->pre_vectors + affd->post_vectors)
	affvecs = nvecs - affd->pre_vectors - affd->post_vectors;
	else
	affvecs = 0;

	/*
	* Simple invocations do not provide a calc_sets() callback. Install
	* the generic one.
	*/
	if (!affd->calc_sets)
	affd->calc_sets = default_calc_sets;

	/* Recalculate the sets */
	affd->calc_sets(affd, affvecs);

	if (WARN_ON_ONCE(affd->nr_sets > IRQ_AFFINITY_MAX_SETS))
	return NULL;

	/* Nothing to assign? */
	if (!affvecs)
	return NULL;

	masks = kcalloc(nvecs, sizeof(*masks), GFP_KERNEL);
	if (!masks)
	return NULL;

	/* Fill out vectors at the beginning that don't need affinity */
	for (curvec = 0; curvec < affd->pre_vectors; curvec++)
	cpumask_copy(&masks[curvec].mask, irq_default_affinity);

	/*
	* Spread on present CPUs starting from affd->pre_vectors. If we
	* have multiple sets, build each sets affinity mask separately.
	*/
	for (i = 0, usedvecs = 0; i < affd->nr_sets; i++) {
	unsigned int this_vecs = affd->set_size[i];
	int ret;

	ret = irq_build_affinity_masks(curvec, this_vecs,
	curvec, masks);
	if (ret) {
	kfree(masks);
	return NULL;
	}
	curvec += this_vecs;
	usedvecs += this_vecs;
	}

	/* Fill out vectors at the end that don't need affinity */
	if (usedvecs >= affvecs)
	curvec = affd->pre_vectors + affvecs;
	else
	curvec = affd->pre_vectors + usedvecs;
	for (; curvec < nvecs; curvec++)
	cpumask_copy(&masks[curvec].mask, irq_default_affinity);

	/* Mark the managed interrupts */
	for (i = affd->pre_vectors; i < nvecs - affd->post_vectors; i++)
	masks[i].is_managed = 1;

	return masks;
	}

	/**
	* irq_calc_affinity_vectors - Calculate the optimal number of vectors
	* @minvec: The minimum number of vectors available
	* @maxvec: The maximum number of vectors available
	* @affd: Description of the affinity requirements
	*/
	unsigned int irq_calc_affinity_vectors(unsigned int minvec, unsigned int maxvec,
	const struct irq_affinity *affd)
	{
	unsigned int resv = affd->pre_vectors + affd->post_vectors;
	unsigned int set_vecs;

	if (resv > minvec)
	return 0;

	if (affd->calc_sets) {
	set_vecs = maxvec - resv;
	} else {
	get_online_cpus();
	set_vecs = cpumask_weight(cpu_possible_mask);
	put_online_cpus();
	}

	return resv + min(set_vecs, maxvec - resv);
	}