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    SubjectRe: [PATCH] virtio_console: Add support for multiple ports for generic guest and host communication
    On (Tue) Sep 29 2009 [14:03:08], Christian Borntraeger wrote:
    > Am Dienstag 29 September 2009 11:24:31 schrieb Amit Shah:
    > > -static void hvc_handle_input(struct virtqueue *vq)
    > > +/* The operations for our console. */
    > > +static struct hv_ops virtio_cons = {
    > > + .get_chars = cons_get_chars,
    > > + .put_chars = cons_put_chars,
    > > + .notifier_add = cons_notifier_add_vio,
    > > + .notifier_del = cons_notifier_del_vio,
    > > + .notifier_hangup = cons_notifier_del_vio,
    > > +};
    > [...]
    > > +int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int))
    > > +{
    > > + virtio_cons.put_chars = put_chars;
    > > + return hvc_instantiate(0, 0, &virtio_cons);
    > > +}
    > [...]
    > > +static int __devinit virtcons_probe(struct virtio_device *vdev)
    > [...]
    > > - /* Start using the new console output. */
    > > - virtio_cons.get_chars = get_chars;
    > > - virtio_cons.put_chars = put_chars;
    >
    > Ok, that wont work for systems that use virtio_cons_early_init. The early
    > put_chars method was replaced by the final one, but these hunks changed that
    > behaviour. Something like the following restores the old behaviour: (only
    > tested on s390)

    Thanks for the testing as well as the patch! Sadly I can only test this
    on qemu and x86, so this is very welcome.

    However:

    > Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
    > If you agree, you can merge this snipped into your big patch.
    >
    > ---
    > drivers/char/virtio_console.c | 3 +++
    > 1 file changed, 3 insertions(+)
    >
    > Index: linux-2.6/drivers/char/virtio_console.c
    > ===================================================================
    > --- linux-2.6.orig/drivers/char/virtio_console.c
    > +++ linux-2.6/drivers/char/virtio_console.c
    > @@ -590,6 +590,9 @@ int init_port_console(struct virtio_cons
    > pr_err("%s: Could not alloc hvc for virtio console port, ret = %d\n",
    > __func__, ret);
    > port->hvc = NULL;
    > + } else {
    > + /* get rid of early put char variants */
    > + virtio_cons.put_chars = cons_put_chars;
    > }
    > return ret;
    > }

    I changed it to look like this, which initializes the final value even
    when hvc_alloc fails. It should work for you I guess.

    I'll merge this in my patch when I send it next.

    Can you please ack the patch?

    Thanks,

    Amit


    From 462aa408c2a1140137d0890ca8043f37b447410d Mon Sep 17 00:00:00 2001
    From: Amit Shah <amit.shah@redhat.com>
    Date: Tue, 29 Sep 2009 17:46:41 +0530
    Subject: [PATCH] virtio_console: fix put_chars after early-init

    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@redhat.com>
    ---
    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().
    *
    --
    1.6.2.5


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