[PATCH v3 3/3] vdpa: Return -EIO if device ack is VIRTIO_NET_ERR in _load_offloads()

[Hawkins Jiawei <yin31149@gmail.com>]

According to VirtIO standard, "The class, command and
command-specific-data are set by the driver,
and the device sets the ack byte.
There is little it can do except issue a diagnostic
if ack is not VIRTIO_NET_OK."

Therefore, QEMU should stop sending the queued SVQ commands and
cancel the device startup if the device's ack is not VIRTIO_NET_OK.

Yet the problem is that, vhost_vdpa_net_load_offloads() returns 1 based on
`*s->status != VIRTIO_NET_OK` when the device's ack is VIRTIO_NET_ERR.
As a result, net->nc->info->load() also returns 1, this makes
vhost_net_start_one() incorrectly assume the device state is
successfully loaded by vhost_vdpa_net_load() and return 0, instead of
goto `fail` label to cancel the device startup, as vhost_net_start_one()
only cancels the device startup when net->nc->info->load() returns a
negative value.

This patch fixes this problem by returning -EIO when the device's
ack is not VIRTIO_NET_OK.

Fixes: 0b58d3686a ("vdpa: Add vhost_vdpa_net_load_offloads()")
Signed-off-by: Hawkins Jiawei <yin31149@gmail.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Eugenio Pérez <eperezma@redhat.com>
---
v3:
 - split the fixes suggested by Eugenio
 - return -EIO suggested by Michael

v2: https://lore.kernel.org/all/69010e9ebb5e3729aef595ed92840f43e48e53e5.1687875592.git.yin31149@gmail.com/
 - fix the same bug in vhost_vdpa_net_load_offloads()

v1: https://lore.kernel.org/all/07a1133d6c989394b342e35d8202257771e76769.1686746406.git.yin31149@gmail.com/

 net/vhost-vdpa.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 03d87e85c8..36aa2d7f8c 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -712,8 +712,11 @@ static int vhost_vdpa_net_load_offloads(VhostVDPAState *s,
     if (unlikely(dev_written < 0)) {
         return dev_written;
     }
+    if (*s->status != VIRTIO_NET_OK) {
+        return -EIO;
+    }
 
-    return *s->status != VIRTIO_NET_OK;
+    return 0;
 }
 
 static int vhost_vdpa_net_load(NetClientState *nc)
-- 
2.25.1