By avoiding cross-CPU usage of the per-cpu iova cache, we can forgo
having a spinlock inside the per-cpu struct. The only place where we
actually may touch another CPU's data is when performing a cache flush
after running out of memory. Here, we can instead schedule a task to run
on the other CPU to do the flush before trying again.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
drivers/iommu/iova.c | 29 ++++++-----------------------
1 file changed, 6 insertions(+), 23 deletions(-)
diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index e23001bfcfee..36cdc8eeab1c 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -390,6 +390,11 @@ free_iova(struct iova_domain *iovad, unsigned long pfn)
}
EXPORT_SYMBOL_GPL(free_iova);
+static void free_this_cached_iovas(void *info)
+{
+ free_cpu_cached_iovas(smp_processor_id(), info);
+}
+
/**
* alloc_iova_fast - allocates an iova from rcache
* @iovad: - iova domain in question
@@ -413,17 +418,12 @@ alloc_iova_fast(struct iova_domain *iovad, unsigned long size,
retry:
new_iova = alloc_iova(iovad, size, limit_pfn, true);
if (!new_iova) {
- unsigned int cpu;
-
if (flushed_rcache)
return 0;
/* Try replenishing IOVAs by flushing rcache. */
flushed_rcache = true;
- preempt_disable();
- for_each_online_cpu(cpu)
- free_cpu_cached_iovas(cpu, iovad);
- preempt_enable();
+ on_each_cpu(free_this_cached_iovas, iovad, true);
goto retry;
}
@@ -647,7 +647,6 @@ struct iova_magazine {
};
struct iova_cpu_rcache {
- spinlock_t lock;
struct iova_magazine *loaded;
struct iova_magazine *prev;
};
@@ -729,7 +728,6 @@ static void init_iova_rcaches(struct iova_domain *iovad)
continue;
for_each_possible_cpu(cpu) {
cpu_rcache = per_cpu_ptr(rcache->cpu_rcaches, cpu);
- spin_lock_init(&cpu_rcache->lock);
cpu_rcache->loaded = iova_magazine_alloc(GFP_KERNEL);
cpu_rcache->prev = iova_magazine_alloc(GFP_KERNEL);
}
@@ -749,10 +747,8 @@ static bool __iova_rcache_insert(struct iova_domain *iovad,
struct iova_magazine *mag_to_free = NULL;
struct iova_cpu_rcache *cpu_rcache;
bool can_insert = false;
- unsigned long flags;
cpu_rcache = get_cpu_ptr(rcache->cpu_rcaches);
- spin_lock_irqsave(&cpu_rcache->lock, flags);
if (!iova_magazine_full(cpu_rcache->loaded)) {
can_insert = true;
@@ -780,7 +776,6 @@ static bool __iova_rcache_insert(struct iova_domain *iovad,
if (can_insert)
iova_magazine_push(cpu_rcache->loaded, iova_pfn);
- spin_unlock_irqrestore(&cpu_rcache->lock, flags);
put_cpu_ptr(rcache->cpu_rcaches);
if (mag_to_free) {
@@ -813,10 +808,8 @@ static unsigned long __iova_rcache_get(struct iova_rcache *rcache,
struct iova_cpu_rcache *cpu_rcache;
unsigned long iova_pfn = 0;
bool has_pfn = false;
- unsigned long flags;
cpu_rcache = get_cpu_ptr(rcache->cpu_rcaches);
- spin_lock_irqsave(&cpu_rcache->lock, flags);
if (!iova_magazine_empty(cpu_rcache->loaded)) {
has_pfn = true;
@@ -836,7 +829,6 @@ static unsigned long __iova_rcache_get(struct iova_rcache *rcache,
if (has_pfn)
iova_pfn = iova_magazine_pop(cpu_rcache->loaded, limit_pfn);
- spin_unlock_irqrestore(&cpu_rcache->lock, flags);
put_cpu_ptr(rcache->cpu_rcaches);
return iova_pfn;
@@ -866,17 +858,11 @@ static void free_cpu_iova_rcache(unsigned int cpu, struct iova_domain *iovad,
struct iova_rcache *rcache)
{
struct iova_cpu_rcache *cpu_rcache = per_cpu_ptr(rcache->cpu_rcaches, cpu);
- unsigned long flags;
-
- spin_lock_irqsave(&cpu_rcache->lock, flags);
-
iova_magazine_free_pfns(cpu_rcache->loaded, iovad);
iova_magazine_free(cpu_rcache->loaded);
iova_magazine_free_pfns(cpu_rcache->prev, iovad);
iova_magazine_free(cpu_rcache->prev);
-
- spin_unlock_irqrestore(&cpu_rcache->lock, flags);
}
/*
@@ -910,16 +896,13 @@ void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain *iovad)
{
struct iova_cpu_rcache *cpu_rcache;
struct iova_rcache *rcache;
- unsigned long flags;
int i;
for (i = 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) {
rcache = &iovad->rcaches[i];
cpu_rcache = per_cpu_ptr(rcache->cpu_rcaches, cpu);
- spin_lock_irqsave(&cpu_rcache->lock, flags);
iova_magazine_free_pfns(cpu_rcache->loaded, iovad);
iova_magazine_free_pfns(cpu_rcache->prev, iovad);
- spin_unlock_irqrestore(&cpu_rcache->lock, flags);
}
}
--
2.8.1
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