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authorMichael S. Tsirkin <mst@redhat.com>2014-05-28 17:07:02 +0300
committerMichael S. Tsirkin <mst@redhat.com>2014-06-09 16:21:06 +0300
commit98f9ca0a3faa99b7388578d55eccecf272be4038 (patch)
tree991e7bc48ed0cb9da73aefe8cf454a54fcf96435 /drivers/vhost
parent23cc5a991c7a9fb7e6d6550e65cee4f4173111c5 (diff)
downloadop-kernel-dev-98f9ca0a3faa99b7388578d55eccecf272be4038.zip
op-kernel-dev-98f9ca0a3faa99b7388578d55eccecf272be4038.tar.gz
vhost: replace rcu with mutex
All memory accesses are done under some VQ mutex. So lock/unlock all VQs is a faster equivalent of synchronize_rcu() for memory access changes. Some guests cause a lot of these changes, so it's helpful to make them faster. Reported-by: "Gonglei (Arei)" <arei.gonglei@huawei.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'drivers/vhost')
-rw-r--r--drivers/vhost/vhost.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 78987e4..1c05e60 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -593,6 +593,7 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
{
struct vhost_memory mem, *newmem, *oldmem;
unsigned long size = offsetof(struct vhost_memory, regions);
+ int i;
if (copy_from_user(&mem, m, size))
return -EFAULT;
@@ -619,7 +620,14 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
oldmem = rcu_dereference_protected(d->memory,
lockdep_is_held(&d->mutex));
rcu_assign_pointer(d->memory, newmem);
- synchronize_rcu();
+
+ /* All memory accesses are done under some VQ mutex.
+ * So below is a faster equivalent of synchronize_rcu()
+ */
+ for (i = 0; i < d->nvqs; ++i) {
+ mutex_lock(&d->vqs[i]->mutex);
+ mutex_unlock(&d->vqs[i]->mutex);
+ }
kfree(oldmem);
return 0;
}
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