[RFC v2 03/10] vhost: add VDUSE API version negotiation

["Eugenio Pérez" <eperezma@redhat.com>]

From: Maxime Coquelin <maxime.coquelin@redhat.com>

As preliminary step to support new VDUSE API version
introducing ASID support, this patch adds API version
negotiation to keep compatibility with older kernels.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 lib/vhost/vduse.c | 14 ++++++++++++--
 lib/vhost/vhost.h |  1 +
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/lib/vhost/vduse.c b/lib/vhost/vduse.c
index 49f2f23b9703..fc52b4cd0703 100644
--- a/lib/vhost/vduse.c
+++ b/lib/vhost/vduse.c
@@ -25,7 +25,7 @@
 #include "vhost.h"
 #include "virtio_net_ctrl.h"
 
-#define VHOST_VDUSE_API_VERSION 0
+#define VHOST_VDUSE_API_VERSION 0ULL
 #define VDUSE_CTRL_PATH "/dev/vduse/control"
 
 struct vduse {
@@ -680,7 +680,7 @@ vduse_device_create(const char *path, bool compliant_ol_flags, bool extbuf, bool
 	uint32_t i, max_queue_pairs, total_queues;
 	struct virtio_net *dev;
 	struct virtio_net_config vnet_config = {{ 0 }};
-	uint64_t ver = VHOST_VDUSE_API_VERSION;
+	uint64_t ver;
 	uint64_t features;
 	const char *name = path + strlen("/dev/vduse/");
 	bool reconnect = false;
@@ -700,6 +700,15 @@ vduse_device_create(const char *path, bool compliant_ol_flags, bool extbuf, bool
 		return -1;
 	}
 
+	if (ioctl(control_fd, VDUSE_GET_API_VERSION, &ver)) {
+		VHOST_CONFIG_LOG(name, ERR, "Failed to get API version: %s", strerror(errno));
+		ret = -1;
+		goto out_ctrl_close;
+	}
+
+	ver = RTE_MIN(ver, VHOST_VDUSE_API_VERSION);
+	VHOST_CONFIG_LOG(name, INFO, "Using VDUSE API version %" PRIu64 "", ver);
+
 	if (ioctl(control_fd, VDUSE_SET_API_VERSION, &ver)) {
 		VHOST_CONFIG_LOG(name, ERR, "Failed to set API version: %" PRIu64 ": %s",
 				ver, strerror(errno));
@@ -800,6 +809,7 @@ vduse_device_create(const char *path, bool compliant_ol_flags, bool extbuf, bool
 	strncpy(dev->ifname, path, IF_NAME_SZ - 1);
 	dev->vduse_ctrl_fd = control_fd;
 	dev->vduse_dev_fd = dev_fd;
+	dev->vduse_api_ver = ver;
 
 	ret = vduse_reconnect_log_map(dev, !reconnect);
 	if (ret < 0)
diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h
index fef493016df5..50b09da5ecf7 100644
--- a/lib/vhost/vhost.h
+++ b/lib/vhost/vhost.h
@@ -532,6 +532,7 @@ struct __rte_cache_aligned virtio_net {
 	int			postcopy_listening;
 	int			vduse_ctrl_fd;
 	int			vduse_dev_fd;
+	uint64_t		vduse_api_ver;
 
 	struct vhost_virtqueue	*cvq;
 
-- 
2.53.0