linux-kernel - Re: [PATCH] virtio_console: Add support for multiple ports for generic guest and host communication

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Date:	Tue, 29 Sep 2009 14:56:56 +0200
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	Amit Shah <amit.shah@...hat.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Alan Cox <alan@...ux.intel.com>,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] virtio_console: Add support for multiple ports for generic guest and host communication

Am Dienstag 29 September 2009 14:20:06 schrieb Amit Shah:
> Christian tested the patch on s390 and found that the output was
> very slow. He tracked it down to put_chars never getting init'ed
> to the final value.
> 
> Signed-off-by: Amit Shah <amit.shah@...hat.com>

Thanks. This fix is 
Acked-by: Christian Borntraeger <borntraeger@...ibm.com>
Tested-by: Christian Borntraeger <borntraeger@...ibm.com> 

I am a bit reluctant to Ack the whole change, since my preference would have
been to not merge virtio serial/console and instead keeping both separate.
We have already managed to clutter all other virtio drivers with tons of 
configuration stuff and feature bits - and every driver uses a different model
for configuration and commands (feature bits, config space, config_change 
indication, extra config virtqueue, commands embedded into the data....).
Using a different device ID for a different use seem like a better way to me.

On the other hand, this patch allows more than one console (I have not tested
this feature) and with this fix applied I dont see any obvious problems.

For the console part I can give a 
Acked-by: Christian Borntraeger <borntraeger@...ibm.com> (console)

Ignoring my preference for having a separate driver and devids, I have no 
opinion about the generic communication stuff - no ack or nack.

> ---
>  drivers/char/virtio_console.c |    8 ++++++++
>  1 files changed, 8 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index 37513e8..598bc0d 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -571,6 +571,14 @@ int init_port_console(struct virtio_console_port
>  *port) * The Host's telling us this port is a console port. Hook it
>  	 * up with an hvc console.
>  	 *
> +	 * We had set the virtio_cons put_chars implementation to
> +	 * put_chars for early_init. Now that we're done with the
> +	 * early init phase, replace it with our cons_put_chars
> +	 * implementation.
> +	 */
> +	virtio_cons.put_chars = cons_put_chars;
> +
> +	/*
>  	 * To set up and manage our virtual console, we call
>  	 * hvc_alloc().
>  	 *

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