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

Eugenio Pérez
2026-03-10T19:17:19Z

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