vhost: use USER_DS in vhost_worker thread
On some architectures address spaces are set up in a way that this is
not necessary to work properly but on some others (like s390) it is.
Make sure we operate on the user address space to allow copy_xxx_user()
from the vhost_worker() thread by setting it explicitly before calling
use_mm() and revert it after unuse_mm().
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 94dbd25..112156f 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -191,7 +191,9 @@
struct vhost_dev *dev = data;
struct vhost_work *work = NULL;
unsigned uninitialized_var(seq);
+ mm_segment_t oldfs = get_fs();
+ set_fs(USER_DS);
use_mm(dev->mm);
for (;;) {
@@ -229,6 +231,7 @@
}
unuse_mm(dev->mm);
+ set_fs(oldfs);
return 0;
}