Linux Virtualization - Mar 2010 - [PATCH 0/6] virtio: console: Fixes, abi update

Hello,

These patches fix a couple of small issues: 
 - generate a kobject change event so that udev is woken up on name
   changes
 - fix a crash after hot-unplug of the first console port and a
   subsequent config update

But majorly, it reworks how ports are discovered: instead of numbering
the ports individually in the host and the guest by just incrementing
a number, we now switch to a bitmap in the config space exposed by the
host to identify active ports. This lets us maintain the same
numbering used by the host and also allows for hot-unplug via the
config space. This is needed for proper migration support after
several hot-plug/unplug operations.

I've tested these patches on my testsuite to catch any regression or
correctness issues. I've also tested all the hotplug-related changes
here.

These should go to 2.6.34, so that we don't push out a stable release
with the older interface. Michael, please forward these to Linus if
everyone is OK with these. I also have a git repo at

git://git.kernel.org/pub/scm/linux/kernel/git/amit/vs-kernel.git master

if you prefer to pull the patches.

Amit Shah (6):
  virtio: console: Generate a kobject CHANGE event on adding 'name'
    attribute
  virtio: console: Check if port is valid in resize_console
  virtio: console: Switch to using a port bitmap for port discovery
  virtio: console: Separate out get_config in a separate function
  virtio: console: Handle hot-plug/unplug config actions
  virtio: console: Remove hot-unplug control message

 drivers/char/virtio_console.c  |  238 ++++++++++++++++++++++++----------------
 include/linux/virtio_console.h |   15 ++-
 2 files changed, 156 insertions(+), 97 deletions(-)

When the host lets us know what 'name' a port is assigned, we create the
sysfs 'name' attribute. Generate a 'change' event after this so
that
udev wakes up and acts on the rules for virtio-ports (currently there's
only one rule that creates a symlink from the 'name' to the actual char
device).

Signed-off-by: Amit Shah <amit.shah at redhat.com>
---
 drivers/char/virtio_console.c |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index f404ccf..67b474b 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -947,11 +947,18 @@ static void handle_control_message(struct ports_device
*portdev,
 		 */
 		err = sysfs_create_group(&port->dev->kobj,
 					 &port_attribute_group);
-		if (err)
+		if (err) {
 			dev_err(port->dev,
 				"Error %d creating sysfs device attributes\n",
 				err);
-
+		} else {
+			/*
+			 * Generate a udev event so that appropriate
+			 * symlinks can be created based on udev
+			 * rules.
+			 */
+			kobject_uevent(&port->dev->kobj, KOBJ_CHANGE);
+		}
 		break;
 	case VIRTIO_CONSOLE_PORT_REMOVE:
 		/*
-- 
1.6.2.5

The console port could have been hot-unplugged. Check if it is valid
before working on it.

Signed-off-by: Amit Shah <amit.shah at redhat.com>
---
 drivers/char/virtio_console.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 67b474b..44288ce 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -681,6 +681,10 @@ static void resize_console(struct port *port)
 	struct virtio_device *vdev;
 	struct winsize ws;
 
+	/* The port could have been hot-unplugged */
+	if (!port)
+		return;
+
 	vdev = port->portdev->vdev;
 	if (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_SIZE)) {
 		vdev->config->get(vdev,
-- 
1.6.2.5

On Fri, Mar 19, 2010 at 05:36:42PM +0530, Amit Shah
wrote:
> Hello,
> 
> These patches fix a couple of small issues: 
>  - generate a kobject change event so that udev is woken up on name
>    changes
>  - fix a crash after hot-unplug of the first console port and a
>    subsequent config update
> 
> But majorly, it reworks how ports are discovered: instead of numbering
> the ports individually in the host and the guest by just incrementing
> a number, we now switch to a bitmap in the config space exposed by the
> host to identify active ports. This lets us maintain the same
> numbering used by the host and also allows for hot-unplug via the
> config space. This is needed for proper migration support after
> several hot-plug/unplug operations.
> 
> I've tested these patches on my testsuite to catch any regression or
> correctness issues. I've also tested all the hotplug-related changes
> here.
> 
> These should go to 2.6.34, so that we don't push out a stable release
> with the older interface.
> 
> Michael, please forward these to Linus if
> everyone is OK with these.
I have some concerns with the new ABI.  I also expect Rusty to be back
in a couple of days, maybe he'll find some time to review the patches.
We'll also have to update the spec ...

Would you like me to queue up the first 2 patches meanwhile?
> I also have a git repo at
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/amit/vs-kernel.git master
> 
> if you prefer to pull the patches.
> Amit Shah (6):
>   virtio: console: Generate a kobject CHANGE event on adding 'name'
>     attribute
>   virtio: console: Check if port is valid in resize_console
>   virtio: console: Switch to using a port bitmap for port discovery
>   virtio: console: Separate out get_config in a separate function
>   virtio: console: Handle hot-plug/unplug config actions
>   virtio: console: Remove hot-unplug control message
> 
>  drivers/char/virtio_console.c  |  238
++++++++++++++++++++++++----------------
>  include/linux/virtio_console.h |   15 ++-
>  2 files changed, 156 insertions(+), 97 deletions(-)