On 1/13/21 2:57 PM, Adrian Moreno wrote:

On 12/20/20 10:13 PM, Maxime Coquelin wrote:

quoted

This patch introduce new callbacks for getting
and setting Virtio features, and implements them
for the different backend types.

Signed-off-by: Maxime Coquelin <redacted>
---
 drivers/net/virtio/virtio_user/vhost.h        |   2 +
 drivers/net/virtio/virtio_user/vhost_kernel.c | 150 +++++++++---------
 .../net/virtio/virtio_user/vhost_kernel_tap.c |  23 +++
 .../net/virtio/virtio_user/vhost_kernel_tap.h |   1 +
 drivers/net/virtio/virtio_user/vhost_user.c   |  63 +++++++-
 drivers/net/virtio/virtio_user/vhost_vdpa.c   |  38 +++--
 .../net/virtio/virtio_user/virtio_user_dev.c  |   5 +-
 drivers/net/virtio/virtio_user_ethdev.c       |   3 +-
 8 files changed, 188 insertions(+), 97 deletions(-)

...

quoted

diff --git a/drivers/net/virtio/virtio_user/vhost_user.c b/drivers/net/virtio/virtio_user/vhost_user.c
index 5ab15318ac..d204fa1eb0 100644
--- a/drivers/net/virtio/virtio_user/vhost_user.c
+++ b/drivers/net/virtio/virtio_user/vhost_user.c

@@ -143,6 +143,62 @@ vhost_user_set_owner(struct virtio_user_dev *dev)
 	return 0;
 }
 
+static int
+vhost_user_get_features(struct virtio_user_dev *dev, uint64_t *features)
+{
+	int ret;
+	struct vhost_user_msg msg = {
+		.request = VHOST_USER_GET_FEATURES,
+		.flags = VHOST_USER_VERSION,
+	};
+
+	ret = vhost_user_write(dev->vhostfd, &msg, NULL, 0);
+	if (ret < 0)
+		goto err;
+
+	ret = vhost_user_read(dev->vhostfd, &msg);
+	if (ret < 0)
+		goto err;
+
+	if (msg.request != VHOST_USER_GET_FEATURES) {
+		PMD_DRV_LOG(ERR, "Unexpected request type (%d)", msg.request);
+		goto err;
+	}
+
+	if (msg.size != sizeof(*features)) {
+		PMD_DRV_LOG(ERR, "Unexpected payload size (%d)", msg.size);
+		goto err;
+	}
+
+	*features = msg.payload.u64;
+
+	return 0;
+err:
+	PMD_DRV_LOG(ERR, "Failed to get backend features");
+

On possibly socket-related errors, it's sometimes useful to print
sterror(errno). WDYT?

quoted

+	return -1;
+}

I agree, I will do it in vhost_user_read/vhost_user_write.
Actually I have a already done it in vhost_user_write after earlier
comment from Chenbo.

Thanks,
Maxime