Re: [Qemu-devel] [PATCH v5] tap: setting error appropriately when calling net_init_tap_one()

[Jason Wang]

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 
Suggested-by: Igor Mammedov 
Suggested-by: Jason Wang 
Signed-off-by: Jay Zhou 
---
  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, );
  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();

  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.

[Qemu-devel] [PATCH v5] tap: setting error appropriately when calling net_init_tap_one()

[Jay Zhou]

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 
Suggested-by: Igor Mammedov 
Suggested-by: Jason Wang 
Signed-off-by: Jay Zhou 
---
 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, );
 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();
 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) {
-- 
1.8.3.1