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DM: handle virtio-console writes when no socket backend is connected

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When virtio-console is used as console port with socket backend,
guest kernel tries to hook it up with hvc console and sets it up.
It doesn't check if a client is connected and can result in ENOTCONN
with virtio-console backend being reset. This will prevent client
connection at a later point. To avoid this, ignore ENOTCONN error.

PS: For Kata, the runtime first launches VM and then proxy which acts
as a client connects to this socket. If this error is not handled,
proxy will never be able to connect as the backend itself will be reset.

Tracked-On: #3189
Signed-off-by: Vijay Dhanraj <vijay.dhanraj@intel.com>
Acked-by: Yu Wang <yu1.wang@intel.com>
This commit is contained in:
Vijay Dhanraj 2019-05-28 17:48:08 -07:00 committed by wenlingz
parent 376fcddff8
commit 19366458f8
1 changed files with 13 additions and 2 deletions
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15
devicemodel/hw/pci/virtio/virtio_console.c
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@ -499,11 +499,22 @@ virtio_console_backend_write(struct virtio_console_port *port, void *arg,
ret = writev(be->fd, iov, niov); ret = writev(be->fd, iov, niov);
if (ret <= 0) { if (ret <= 0) {
/* backend cannot receive more data. For example when pts is /* Case 1:backend cannot receive more data. For example when pts is
* not connected to any client, its tty buffer will become full. * not connected to any client, its tty buffer will become full.
* In this case we just drop data from guest hvc console. * In this case we just drop data from guest hvc console.
*
* Case 2: Backend connection not yet setup. For example, when
* virtio-console is used as console port with socket backend, guest
* kernel tries to hook it up with hvc console and sets it up. It
* doesn't check if a client is connected and can result in ENOTCONN
* with virtio-console backend being reset. This will prevent
* client connection at a later point. To avoid this, ignore
* ENOTCONN error.
*
* PS: For Kata, the runtime first launches VM and then proxy which
* acts as a client connects to this socket.
*/ */
if (ret == -1 && errno == EAGAIN) if (ret == -1 && (errno == EAGAIN || errno == ENOTCONN))
return; return;
virtio_console_reset_backend(be); virtio_console_reset_backend(be);