[RFC PATCH V3 4/5] vhost: introduce helpers to get the size of metadata area

[Jason Wang]

Signed-off-by: Jason Wang <jasow...@redhat.com>
---
 drivers/vhost/vhost.c | 46 ++++++++++++++++++++++++++-----------------
 1 file changed, 28 insertions(+), 18 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 27b5c03feaac..54b43feef8d9 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -489,6 +489,27 @@ bool vhost_dev_has_owner(struct vhost_dev *dev)
 }
 EXPORT_SYMBOL_GPL(vhost_dev_has_owner);
 
+static size_t vhost_get_avail_size(struct vhost_virtqueue *vq, int num)
+{
+       size_t event = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
+
+       return sizeof(*vq->avail) +
+              sizeof(*vq->avail->ring) * num + event;
+}
+
+static size_t vhost_get_used_size(struct vhost_virtqueue *vq, int num)
+{
+       size_t event = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
+
+       return sizeof(*vq->used) +
+              sizeof(*vq->used->ring) * num + event;
+}
+
+static size_t vhost_get_desc_size(struct vhost_virtqueue *vq, int num)
+{
+       return sizeof(*vq->desc) * num;
+}
+
 /* Caller should have device mutex */
 long vhost_dev_set_owner(struct vhost_dev *dev)
 {
@@ -1248,13 +1269,9 @@ static bool vq_access_ok(struct vhost_virtqueue *vq, 
unsigned int num,
                         struct vring_used __user *used)
 
 {
-       size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
-
-       return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
-              access_ok(VERIFY_READ, avail,
-                        sizeof *avail + num * sizeof *avail->ring + s) &&
-              access_ok(VERIFY_WRITE, used,
-                       sizeof *used + num * sizeof *used->ring + s);
+       return access_ok(VERIFY_READ, desc, vhost_get_desc_size(vq, num)) &&
+              access_ok(VERIFY_READ, avail, vhost_get_avail_size(vq, num)) &&
+              access_ok(VERIFY_WRITE, used, vhost_get_used_size(vq, num));
 }
 
 static void vhost_vq_meta_update(struct vhost_virtqueue *vq,
@@ -1306,22 +1323,18 @@ static bool iotlb_access_ok(struct vhost_virtqueue *vq,
 
 int vq_meta_prefetch(struct vhost_virtqueue *vq)
 {
-       size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
        unsigned int num = vq->num;
 
        if (!vq->iotlb)
                return 1;
 
        return iotlb_access_ok(vq, VHOST_ACCESS_RO, (u64)(uintptr_t)vq->desc,
-                              num * sizeof(*vq->desc), VHOST_ADDR_DESC) &&
+                              vhost_get_desc_size(vq, num), VHOST_ADDR_DESC) &&
               iotlb_access_ok(vq, VHOST_ACCESS_RO, (u64)(uintptr_t)vq->avail,
-                              sizeof *vq->avail +
-                              num * sizeof(*vq->avail->ring) + s,
+                              vhost_get_avail_size(vq, num),
                               VHOST_ADDR_AVAIL) &&
               iotlb_access_ok(vq, VHOST_ACCESS_WO, (u64)(uintptr_t)vq->used,
-                              sizeof *vq->used +
-                              num * sizeof(*vq->used->ring) + s,
-                              VHOST_ADDR_USED);
+                              vhost_get_used_size(vq, num), VHOST_ADDR_USED);
 }
 EXPORT_SYMBOL_GPL(vq_meta_prefetch);
 
@@ -1338,13 +1351,10 @@ EXPORT_SYMBOL_GPL(vhost_log_access_ok);
 static bool vq_log_access_ok(struct vhost_virtqueue *vq,
                             void __user *log_base)
 {
-       size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
-
        return vq_memory_access_ok(log_base, vq->umem,
                                   vhost_has_feature(vq, VHOST_F_LOG_ALL)) &&
                (!vq->log_used || log_access_ok(log_base, vq->log_addr,
-                                       sizeof *vq->used +
-                                       vq->num * sizeof *vq->used->ring + s));
+                                 vhost_get_used_size(vq, vq->num)));
 }
 
 /* Can we start vq? */
-- 
2.17.1

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