[PATCH 03/40] vdpa: probe descriptor group index for data vqs

[Si-Wei Liu <si-wei.liu@oracle.com>]

Getting it ahead at initialization time instead of start time allows
decision making independent of device status, while reducing failure
possibility in starting device or during migration.

Adding function vhost_vdpa_probe_desc_group() for that end. This
function will be used to probe the descriptor group for data vqs.

Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
---
 net/vhost-vdpa.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 887c329..0cf3147 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -1688,6 +1688,95 @@ out:
     return r;
 }
 
+static int vhost_vdpa_probe_desc_group(int device_fd, uint64_t features,
+                                       int vq_index, int64_t *desc_grpidx,
+                                       Error **errp)
+{
+    uint64_t backend_features;
+    int64_t vq_group, desc_group;
+    uint8_t saved_status = 0;
+    uint8_t status = 0;
+    int r;
+
+    ERRP_GUARD();
+
+    r = ioctl(device_fd, VHOST_GET_BACKEND_FEATURES, &backend_features);
+    if (unlikely(r < 0)) {
+        error_setg_errno(errp, errno, "Cannot get vdpa backend_features");
+        return r;
+    }
+
+    if (!(backend_features & BIT_ULL(VHOST_BACKEND_F_IOTLB_ASID))) {
+        return 0;
+    }
+
+    if (!(backend_features & BIT_ULL(VHOST_BACKEND_F_DESC_ASID))) {
+        return 0;
+    }
+
+    r = ioctl(device_fd, VHOST_VDPA_GET_STATUS, &saved_status);
+    if (unlikely(r)) {
+        error_setg_errno(errp, -r, "Cannot get device status");
+        goto out;
+    }
+
+    r = ioctl(device_fd, VHOST_VDPA_SET_STATUS, &status);
+    if (unlikely(r)) {
+        error_setg_errno(errp, -r, "Cannot reset device");
+        goto out;
+    }
+
+    r = ioctl(device_fd, VHOST_SET_FEATURES, &features);
+    if (unlikely(r)) {
+        error_setg_errno(errp, errno, "Cannot set features");
+    }
+
+    status = VIRTIO_CONFIG_S_ACKNOWLEDGE |
+             VIRTIO_CONFIG_S_DRIVER |
+             VIRTIO_CONFIG_S_FEATURES_OK;
+
+    r = ioctl(device_fd, VHOST_VDPA_SET_STATUS, &status);
+    if (unlikely(r)) {
+        error_setg_errno(errp, -r, "Cannot set device status");
+        goto out;
+    }
+
+    vq_group = vhost_vdpa_get_vring_group(device_fd, vq_index, errp);
+    if (unlikely(vq_group < 0)) {
+        if (vq_group != -ENOTSUP) {
+            r = vq_group;
+            goto out;
+        }
+
+        /*
+         * The kernel report VHOST_BACKEND_F_IOTLB_ASID if the vdpa frontend
+         * support ASID even if the parent driver does not.
+         */
+        error_free(*errp);
+        *errp = NULL;
+        r = 0;
+        goto out;
+    }
+
+    desc_group = vhost_vdpa_get_vring_desc_group(device_fd, vq_index,
+                                                 errp);
+    if (unlikely(desc_group < 0)) {
+        r = desc_group;
+        goto out;
+    } else if (desc_group != vq_group) {
+        *desc_grpidx = desc_group;
+    }
+    r = 1;
+
+out:
+    status = 0;
+    ioctl(device_fd, VHOST_VDPA_SET_STATUS, &status);
+    if (saved_status) {
+        ioctl(device_fd, VHOST_VDPA_SET_STATUS, &saved_status);
+    }
+    return r;
+}
+
 static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
                                        const char *device,
                                        const char *name,
-- 
1.8.3.1