redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

iommu/iova: Add flush counters to Flush-Queue implementation 

There are two counters:

	* fq_flush_start_cnt  - Increased when a TLB flush
	                        is started.

	* fq_flush_finish_cnt - Increased when a TLB flush
				is finished.

The fq_flush_start_cnt is assigned to every Flush-Queue
entry on its creation. When freeing entries from the
Flush-Queue, the value in the entry is compared to the
fq_flush_finish_cnt. The entry can only be freed when its
value is less than the value of fq_flush_finish_cnt.

The reason for these counters it to take advantage of IOMMU
TLB flushes that happened on other CPUs. These already
flushed the TLB for Flush-Queue entries on other CPUs so
that they can already be freed without flushing the TLB
again.

This makes it less likely that the Flush-Queue is full and
saves IOMMU TLB flushes.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
hifive-unleashed-5.1
Joerg Roedel 2017-08-10 16:14:59 +02:00
parent 1928210107
commit fb418dab8a
2 changed files with 33 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
drivers/iommu/iova.c
View File

@ -75,6 +75,9 @@ int init_iova_flush_queue(struct iova_domain *iovad,
{
int cpu;
atomic64_set(&iovad->fq_flush_start_cnt, 0);
atomic64_set(&iovad->fq_flush_finish_cnt, 0);
iovad->fq = alloc_percpu(struct iova_fq);
if (!iovad->fq)
return -ENOMEM;
@ -482,20 +485,30 @@ static inline unsigned fq_ring_add(struct iova_fq *fq)
static void fq_ring_free(struct iova_domain *iovad, struct iova_fq *fq)
{
u64 counter = atomic64_read(&iovad->fq_flush_finish_cnt);
unsigned idx;
fq_ring_for_each(idx, fq) {
if (fq->entries[idx].counter >= counter)
break;
if (iovad->entry_dtor)
iovad->entry_dtor(fq->entries[idx].data);
free_iova_fast(iovad,
fq->entries[idx].iova_pfn,
fq->entries[idx].pages);
}
fq->head = 0;
fq->tail = 0;
fq->head = (fq->head + 1) % IOVA_FQ_SIZE;
}
}
static void iova_domain_flush(struct iova_domain *iovad)
{
atomic64_inc(&iovad->fq_flush_start_cnt);
iovad->flush_cb(iovad);
atomic64_inc(&iovad->fq_flush_finish_cnt);
}
static void fq_destroy_all_entries(struct iova_domain *iovad)
@ -526,8 +539,15 @@ void queue_iova(struct iova_domain *iovad,
struct iova_fq *fq = get_cpu_ptr(iovad->fq);
unsigned idx;
/*
* First remove all entries from the flush queue that have already been
* flushed out on another CPU. This makes the fq_full() check below less
* likely to be true.
*/
fq_ring_free(iovad, fq);
if (fq_full(fq)) {
iovad->flush_cb(iovad);
iova_domain_flush(iovad);
fq_ring_free(iovad, fq);
}
@ -536,6 +556,7 @@ void queue_iova(struct iova_domain *iovad,
fq->entries[idx].iova_pfn = pfn;
fq->entries[idx].pages = pages;
fq->entries[idx].data = data;
fq->entries[idx].counter = atomic64_read(&iovad->fq_flush_start_cnt);
put_cpu_ptr(iovad->fq);
}

8
include/linux/iova.h
View File

@ -14,6 +14,7 @@
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/rbtree.h>
#include <linux/atomic.h>
#include <linux/dma-mapping.h>
/* iova structure */
@ -52,6 +53,7 @@ struct iova_fq_entry {
unsigned long iova_pfn;
unsigned long pages;
unsigned long data;
u64 counter; /* Flush counter when this entrie was added */
};
/* Per-CPU Flush Queue structure */
@ -77,6 +79,12 @@ struct iova_domain {
iova entry */
struct iova_fq __percpu *fq; /* Flush Queue */
atomic64_t fq_flush_start_cnt; /* Number of TLB flushes that
have been started */
atomic64_t fq_flush_finish_cnt; /* Number of TLB flushes that
have been finished */
};
static inline unsigned long iova_size(struct iova *iova)