[PATCH v3 1/3] vdpa: Return -EIO if device ack is VIRTIO_NET_ERR in _load_mac()

[Hawkins Jiawei]

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_mac() 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: f73c0c43ac ("vdpa: extract vhost_vdpa_net_load_mac from 
vhost_vdpa_net_load")
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, 3 insertions(+), 2 deletions(-)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index e19ab063fa..ee273c40ca 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -646,8 +646,9 @@ static int vhost_vdpa_net_load_mac(VhostVDPAState *s, const 
VirtIONet *n)
         if (unlikely(dev_written < 0)) {
             return dev_written;
         }
-
-        return *s->status != VIRTIO_NET_OK;
+        if (*s->status != VIRTIO_NET_OK) {
+            return -EIO;
+        }
     }
 
     return 0;
-- 
2.25.1