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Message-ID: <157919867745.21002.3239982207630090516.stgit@gimli.home>
Date: Thu, 16 Jan 2020 11:17:57 -0700
From: Alex Williamson <alex.williamson@...hat.com>
To: yan.y.zhao@...el.com
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 1/3] vfio/type1: Convert vfio_iommu.lock from mutex to
rwsem
As a first step reducing lock contention, maintain the same locking
granularity using a rwsem rather than a mutex.
Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
---
drivers/vfio/vfio_iommu_type1.c | 51 ++++++++++++++++++++-------------------
1 file changed, 26 insertions(+), 25 deletions(-)
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 2ada8e6cdb88..7ae58350af5b 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -28,6 +28,7 @@
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/rbtree.h>
+#include <linux/rwsem.h>
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>
#include <linux/slab.h>
@@ -64,7 +65,7 @@ struct vfio_iommu {
struct list_head domain_list;
struct list_head iova_list;
struct vfio_domain *external_domain; /* domain for external user */
- struct mutex lock;
+ struct rw_semaphore lock;
struct rb_root dma_list;
struct blocking_notifier_head notifier;
unsigned int dma_avail;
@@ -538,7 +539,7 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
if (!iommu->v2)
return -EACCES;
- mutex_lock(&iommu->lock);
+ down_write(&iommu->lock);
/* Fail if notifier list is empty */
if (!iommu->notifier.head) {
@@ -602,7 +603,7 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
phys_pfn[j] = 0;
}
pin_done:
- mutex_unlock(&iommu->lock);
+ up_write(&iommu->lock);
return ret;
}
@@ -621,7 +622,7 @@ static int vfio_iommu_type1_unpin_pages(void *iommu_data,
if (!iommu->v2)
return -EACCES;
- mutex_lock(&iommu->lock);
+ down_write(&iommu->lock);
do_accounting = !IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu);
for (i = 0; i < npage; i++) {
@@ -636,7 +637,7 @@ static int vfio_iommu_type1_unpin_pages(void *iommu_data,
}
unpin_exit:
- mutex_unlock(&iommu->lock);
+ up_write(&iommu->lock);
return i > npage ? npage : (i > 0 ? i : -EINVAL);
}
@@ -829,10 +830,10 @@ static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
struct vfio_domain *domain;
unsigned long bitmap = ULONG_MAX;
- mutex_lock(&iommu->lock);
+ down_write(&iommu->lock);
list_for_each_entry(domain, &iommu->domain_list, next)
bitmap &= domain->domain->pgsize_bitmap;
- mutex_unlock(&iommu->lock);
+ up_write(&iommu->lock);
/*
* In case the IOMMU supports page sizes smaller than PAGE_SIZE
@@ -870,7 +871,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
WARN_ON(mask & PAGE_MASK);
again:
- mutex_lock(&iommu->lock);
+ down_write(&iommu->lock);
/*
* vfio-iommu-type1 (v1) - User mappings were coalesced together to
@@ -945,7 +946,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
* Vendor drivers MUST unpin pages in response to an
* invalidation.
*/
- mutex_unlock(&iommu->lock);
+ up_write(&iommu->lock);
blocking_notifier_call_chain(&iommu->notifier,
VFIO_IOMMU_NOTIFY_DMA_UNMAP,
&nb_unmap);
@@ -956,7 +957,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
}
unlock:
- mutex_unlock(&iommu->lock);
+ up_write(&iommu->lock);
/* Report how much was unmapped */
unmap->size = unmapped;
@@ -1081,7 +1082,7 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
if (iova + size - 1 < iova || vaddr + size - 1 < vaddr)
return -EINVAL;
- mutex_lock(&iommu->lock);
+ down_write(&iommu->lock);
if (vfio_find_dma(iommu, iova, size)) {
ret = -EEXIST;
@@ -1150,7 +1151,7 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
ret = vfio_pin_map_dma(iommu, dma, size);
out_unlock:
- mutex_unlock(&iommu->lock);
+ up_write(&iommu->lock);
return ret;
}
@@ -1645,18 +1646,18 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
LIST_HEAD(iova_copy);
LIST_HEAD(group_resv_regions);
- mutex_lock(&iommu->lock);
+ down_write(&iommu->lock);
list_for_each_entry(d, &iommu->domain_list, next) {
if (find_iommu_group(d, iommu_group)) {
- mutex_unlock(&iommu->lock);
+ up_write(&iommu->lock);
return -EINVAL;
}
}
if (iommu->external_domain) {
if (find_iommu_group(iommu->external_domain, iommu_group)) {
- mutex_unlock(&iommu->lock);
+ up_write(&iommu->lock);
return -EINVAL;
}
}
@@ -1693,7 +1694,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
list_add(&group->next,
&iommu->external_domain->group_list);
- mutex_unlock(&iommu->lock);
+ up_write(&iommu->lock);
return 0;
}
@@ -1815,7 +1816,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
done:
/* Delete the old one and insert new iova list */
vfio_iommu_iova_insert_copy(iommu, &iova_copy);
- mutex_unlock(&iommu->lock);
+ up_write(&iommu->lock);
vfio_iommu_resv_free(&group_resv_regions);
return 0;
@@ -1829,7 +1830,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
out_free:
kfree(domain);
kfree(group);
- mutex_unlock(&iommu->lock);
+ up_write(&iommu->lock);
return ret;
}
@@ -1969,7 +1970,7 @@ static void vfio_iommu_type1_detach_group(void *iommu_data,
struct vfio_group *group;
LIST_HEAD(iova_copy);
- mutex_lock(&iommu->lock);
+ down_write(&iommu->lock);
if (iommu->external_domain) {
group = find_iommu_group(iommu->external_domain, iommu_group);
@@ -2033,7 +2034,7 @@ static void vfio_iommu_type1_detach_group(void *iommu_data,
vfio_iommu_iova_free(&iova_copy);
detach_group_done:
- mutex_unlock(&iommu->lock);
+ up_write(&iommu->lock);
}
static void *vfio_iommu_type1_open(unsigned long arg)
@@ -2062,7 +2063,7 @@ static void *vfio_iommu_type1_open(unsigned long arg)
INIT_LIST_HEAD(&iommu->iova_list);
iommu->dma_list = RB_ROOT;
iommu->dma_avail = dma_entry_limit;
- mutex_init(&iommu->lock);
+ init_rwsem(&iommu->lock);
BLOCKING_INIT_NOTIFIER_HEAD(&iommu->notifier);
return iommu;
@@ -2114,14 +2115,14 @@ static int vfio_domains_have_iommu_cache(struct vfio_iommu *iommu)
struct vfio_domain *domain;
int ret = 1;
- mutex_lock(&iommu->lock);
+ down_write(&iommu->lock);
list_for_each_entry(domain, &iommu->domain_list, next) {
if (!(domain->prot & IOMMU_CACHE)) {
ret = 0;
break;
}
}
- mutex_unlock(&iommu->lock);
+ up_write(&iommu->lock);
return ret;
}
@@ -2155,7 +2156,7 @@ static int vfio_iommu_iova_build_caps(struct vfio_iommu *iommu,
size_t size;
int iovas = 0, i = 0, ret;
- mutex_lock(&iommu->lock);
+ down_write(&iommu->lock);
list_for_each_entry(iova, &iommu->iova_list, list)
iovas++;
@@ -2189,7 +2190,7 @@ static int vfio_iommu_iova_build_caps(struct vfio_iommu *iommu,
kfree(cap_iovas);
out_unlock:
- mutex_unlock(&iommu->lock);
+ up_write(&iommu->lock);
return ret;
}
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