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Re: [Qemu-devel] [PATCH v5] tap: setting error appropriately when callin


From: Jason Wang
Subject: Re: [Qemu-devel] [PATCH v5] tap: setting error appropriately when calling net_init_tap_one()
Date: Fri, 2 Mar 2018 17:55:12 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0



On 2018年03月02日 17:04, Jay Zhou wrote:
If netdev_add tap,id=net0,...,vhost=on failed in net_init_tap_one(),
the followed up device_add virtio-net-pci,netdev=net0 will fail
too, prints:

    TUNSETOFFLOAD ioctl() failed: Bad file descriptor TUNSETOFFLOAD
    ioctl() failed: Bad file descriptor

The reason is that the fd of tap is closed when error occured after
calling net_init_tap_one().

The fd should be closed when calling net_init_tap_one failed:
    - if tap_set_sndbuf() failed
    - if tap_set_sndbuf() succeeded but vhost failed to open or
      initialize with vhostforce flag on
    - with wrong vhost command line parameter
The fd should not be closed just because vhost failed to open or
initialize but without vhostforce flag. So the followed up
device_add can fall back to userspace virtio successfully.

Suggested-by: Michael S. Tsirkin <address@hidden>
Suggested-by: Igor Mammedov <address@hidden>
Suggested-by: Jason Wang <address@hidden>
Signed-off-by: Jay Zhou <address@hidden>
---
  include/net/vhost_net.h |  3 +++
  net/tap.c               | 22 +++++++++++++++++-----
  2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
index afc1499..77e4739 100644
--- a/include/net/vhost_net.h
+++ b/include/net/vhost_net.h
@@ -4,6 +4,9 @@
  #include "net/net.h"
  #include "hw/virtio/vhost-backend.h"
+#define VHOST_NET_INIT_FAILED \
+    "vhost-net requested but could not be initialized"
+
  struct vhost_net;
  typedef struct vhost_net VHostNetState;
diff --git a/net/tap.c b/net/tap.c
index 979e622..2b3a36f 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -686,14 +686,23 @@ static void net_init_tap_one(const NetdevTapOptions *tap, 
NetClientState *peer,
          if (vhostfdname) {
              vhostfd = monitor_fd_param(cur_mon, vhostfdname, &err);
              if (vhostfd == -1) {
-                error_propagate(errp, err);
+                if (tap->has_vhostforce && tap->vhostforce) {
+                    error_propagate(errp, err);
+                } else {
+                    warn_report_err(err);
+                }
                  return;
              }
          } else {
              vhostfd = open("/dev/vhost-net", O_RDWR);
              if (vhostfd < 0) {
-                error_setg_errno(errp, errno,
-                                 "tap: open vhost char device failed");
+                if (tap->has_vhostforce && tap->vhostforce) {
+                    error_setg_errno(errp, errno,
+                                     "tap: open vhost char device failed");
+                } else {
+                    warn_report("tap: open vhost char device failed: %s",
+                                strerror(errno));
+                }
                  return;
              }
              fcntl(vhostfd, F_SETFL, O_NONBLOCK);
@@ -702,8 +711,11 @@ static void net_init_tap_one(const NetdevTapOptions *tap, 
NetClientState *peer,
s->vhost_net = vhost_net_init(&options);
          if (!s->vhost_net) {
-            error_setg(errp,
-                       "vhost-net requested but could not be initialized");
+            if (tap->has_vhostforce && tap->vhostforce) {
+                error_setg(errp, VHOST_NET_INIT_FAILED);
+            } else {
+                warn_report(VHOST_NET_INIT_FAILED);
+            }
              return;
          }
      } else if (vhostfdname) {

Applied, thanks.




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