vhost: add helper to parse userspace vring state/file

The next patches add new vhost worker ioctls which will need to get a
vhost_virtqueue from a userspace struct which specifies the vq's index.
This moves the vhost_vring_ioctl code to do this to a helper so it can
be shared.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Message-Id: <20230626232307.97930-14-michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 6cadbc6..12203d3 100644 (file)
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -599,6 +599,27 @@ free_worker:
        return NULL;
 }
 
+static int vhost_get_vq_from_user(struct vhost_dev *dev, void __user *argp,
+                                 struct vhost_virtqueue **vq, u32 *id)
+{
+       u32 __user *idxp = argp;
+       u32 idx;
+       long r;
+
+       r = get_user(idx, idxp);
+       if (r < 0)
+               return r;
+
+       if (idx >= dev->nvqs)
+               return -ENOBUFS;
+
+       idx = array_index_nospec(idx, dev->nvqs);
+
+       *vq = dev->vqs[idx];
+       *id = idx;
+       return 0;
+}
+
 /* Caller should have device mutex */
 long vhost_dev_set_owner(struct vhost_dev *dev)
 {
@@ -1618,21 +1639,15 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
        struct file *eventfp, *filep = NULL;
        bool pollstart = false, pollstop = false;
        struct eventfd_ctx *ctx = NULL;
-       u32 __user *idxp = argp;
        struct vhost_virtqueue *vq;
        struct vhost_vring_state s;
        struct vhost_vring_file f;
        u32 idx;
        long r;
 
-       r = get_user(idx, idxp);
+       r = vhost_get_vq_from_user(d, argp, &vq, &idx);
        if (r < 0)
                return r;
-       if (idx >= d->nvqs)
-               return -ENOBUFS;
-
-       idx = array_index_nospec(idx, d->nvqs);
-       vq = d->vqs[idx];
 
        if (ioctl == VHOST_SET_VRING_NUM ||
            ioctl == VHOST_SET_VRING_ADDR) {