Commit 876b598e authored by Zhang Zekun's avatar Zhang Zekun
Browse files

iommu/iova: Make the rcache depot scale better 

mainline inclusion
from mainline-v6.7-rc1
commit 911aa1245da83ff5e76d33bb612d8b5a3f2ec4a5
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8KS9A
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=911aa1245da83ff5e76d33bb612d8b5a3f2ec4a5



--------------------------------------

The algorithm in the original paper specifies the storage of full
magazines in the depot as an unbounded list rather than a fixed-size
array. It turns out to be pretty straightforward to do this in our
implementation with no significant loss of efficiency. This allows
the depot to scale up to the working set sizes of larger systems,
while also potentially saving some memory on smaller ones too.

Since this involves touching struct iova_magazine with the requisite
care, we may as well reinforce the comment with a proper assertion too.

Reviewed-by: default avatarJohn Garry <john.g.garry@oracle.com>
Reviewed-by: default avatarJerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: default avatarRobin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/f597aa72fc3e1d315bc4574af0ce0ebe5c31cd22.1694535580.git.robin.murphy@arm.com


Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarZhang Zekun <zhangzekun11@huawei.com>
parent 26164f20

drivers/iommu/iova.c

+28 −20
Original line number Diff line number Diff line
@@ -795,14 +795,19 @@ split_and_remove_iova(struct iova_domain *iovad, struct iova *iova, 
/*

 * As kmalloc's buffer size is fixed to power of 2, 127 is chosen to

 * assure size of 'iova_magazine' to be 1024 bytes, so that no memory

 * will be wasted.

 * will be wasted. Since only full magazines are inserted into the depot,

 * we don't need to waste PFN capacity on a separate list head either.

 */

#define IOVA_MAG_SIZE 127



struct iova_magazine {

	union {

		unsigned long size;

		struct iova_magazine *next;

	};

	unsigned long pfns[IOVA_MAG_SIZE];

};

static_assert(!(sizeof(struct iova_magazine) & (sizeof(struct iova_magazine) - 1)));



struct iova_cpu_rcache {

	spinlock_t lock;
@@ -882,6 +887,21 @@ static void iova_magazine_push(struct iova_magazine *mag, unsigned long pfn) 
	mag->pfns[mag->size++] = pfn;

}



static struct iova_magazine *iova_depot_pop(struct iova_rcache *rcache)

{

	struct iova_magazine *mag = rcache->depot;



	rcache->depot = mag->next;

	mag->size = IOVA_MAG_SIZE;

	return mag;

}



static void iova_depot_push(struct iova_rcache *rcache, struct iova_magazine *mag)

{

	mag->next = rcache->depot;

	rcache->depot = mag;

}



static void init_iova_rcaches(struct iova_domain *iovad)

{

	struct iova_cpu_rcache *cpu_rcache;
@@ -892,7 +912,6 @@ static void init_iova_rcaches(struct iova_domain *iovad) 
	for (i = 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) {

		rcache = &iovad->rcaches[i];

		spin_lock_init(&rcache->lock);

		rcache->depot_size = 0;

		rcache->cpu_rcaches = __alloc_percpu(sizeof(*cpu_rcache), cache_line_size());

		if (WARN_ON(!rcache->cpu_rcaches))

			continue;
@@ -915,7 +934,6 @@ static bool __iova_rcache_insert(struct iova_domain *iovad, 
				 struct iova_rcache *rcache,

				 unsigned long iova_pfn)

{

	struct iova_magazine *mag_to_free = NULL;

	struct iova_cpu_rcache *cpu_rcache;

	bool can_insert = false;

	unsigned long flags;
@@ -933,12 +951,7 @@ static bool __iova_rcache_insert(struct iova_domain *iovad, 


		if (new_mag) {

			spin_lock(&rcache->lock);

			if (rcache->depot_size < MAX_GLOBAL_MAGS) {

				rcache->depot[rcache->depot_size++] =

						cpu_rcache->loaded;

			} else {

				mag_to_free = cpu_rcache->loaded;

			}

			iova_depot_push(rcache, cpu_rcache->loaded);

			spin_unlock(&rcache->lock);



			cpu_rcache->loaded = new_mag;
@@ -951,11 +964,6 @@ static bool __iova_rcache_insert(struct iova_domain *iovad, 


	spin_unlock_irqrestore(&cpu_rcache->lock, flags);



	if (mag_to_free) {

		iova_magazine_free_pfns(mag_to_free, iovad);

		iova_magazine_free(mag_to_free);

	}



	return can_insert;

}
@@ -993,9 +1001,9 @@ static unsigned long __iova_rcache_get(struct iova_rcache *rcache, 
		has_pfn = true;

	} else {

		spin_lock(&rcache->lock);

		if (rcache->depot_size > 0) {

		if (rcache->depot) {

			iova_magazine_free(cpu_rcache->loaded);

			cpu_rcache->loaded = rcache->depot[--rcache->depot_size];

			cpu_rcache->loaded = iova_depot_pop(rcache);

			has_pfn = true;

		}

		spin_unlock(&rcache->lock);
@@ -1034,7 +1042,7 @@ static void free_iova_rcaches(struct iova_domain *iovad) 
	struct iova_rcache *rcache;

	struct iova_cpu_rcache *cpu_rcache;

	unsigned int cpu;

	int i, j;

	int i;



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

		rcache = &iovad->rcaches[i];
@@ -1044,8 +1052,8 @@ static void free_iova_rcaches(struct iova_domain *iovad) 
			iova_magazine_free(cpu_rcache->prev);

		}

		free_percpu(rcache->cpu_rcaches);

		for (j = 0; j < rcache->depot_size; ++j)

			iova_magazine_free(rcache->depot[j]);

		while (rcache->depot)

			iova_magazine_free(iova_depot_pop(rcache));

	}

}

include/linux/iova.h

+1 −3
Original line number Diff line number Diff line
@@ -26,12 +26,10 @@ struct iova_magazine; 
struct iova_cpu_rcache;



#define IOVA_RANGE_CACHE_MAX_SIZE 6	/* log of max cached IOVA range size (in pages) */

#define MAX_GLOBAL_MAGS 32	/* magazines per bin */



struct iova_rcache {

	spinlock_t lock;

	unsigned long depot_size;

	struct iova_magazine *depot[MAX_GLOBAL_MAGS];

	struct iova_magazine *depot;

	struct iova_cpu_rcache __percpu *cpu_rcaches;

};