Attachment 918736 Details for Bug 616772 – Proposed patch

[patch] Proposed patch

0001-virtio-serial-expose-a-guest_writable-callback-for-u.patch (text/plain), 2.60 KB, created by Amit Shah on 2014-07-17 14:39:51 UTC

(hide)

Description:

Filename:

MIME Type:

Creator: Amit Shah

Created: 2014-07-17 14:39:51 UTC

Size: 2.60 KB

patch

obsolete

>From 7ecde509d5c62583651c1dd028925a8654ab3eb8 Mon Sep 17 00:00:00 2001
>Message-Id: <7ecde509d5c62583651c1dd028925a8654ab3eb8.1405607848.git.amit.shah@redhat.com>
>From: Amit Shah <amit.shah@redhat.com>
>Date: Thu, 17 Jul 2014 20:02:45 +0530
>Subject: [PATCH 1/1] virtio: serial: expose a 'guest_writable' callback for
> users
>
>Users of virtio-serial may want to know when a port becomes writable.  A
>port can stop accepting writes if the guest port is open but not being
>read from.  In this case, data gets queued up in the virtqueue, and
>after the vq is full, writes to the port do not succeed.
>
>When the guest reads off a vq element, and adds a new one for the host
>to put data in, we can tell users the port is available for more writes,
>via the new ->guest_writable() callback.
>
>Requested-by: Alon Levy <alevy@redhat.com>
>Signed-off-by: Amit Shah <amit.shah@redhat.com>
>---
> hw/char/virtio-serial-bus.c       | 18 ++++++++++++++++++
> include/hw/virtio/virtio-serial.h |  3 +++
> 2 files changed, 21 insertions(+)
>
>diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
>index 23123b7..4ae00f1 100644
>--- a/hw/char/virtio-serial-bus.c
>+++ b/hw/char/virtio-serial-bus.c
>@@ -445,6 +445,24 @@ static void handle_output(VirtIODevice *vdev, VirtQueue *vq)
> 
> static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
> {
>+    /*
>+     * Users of virtio-serial would like to know when guest becomes
>+     * writable again -- i.e. if a vq had stuff queued up and the
>+     * guest wasn't reading at all, the host would not be able to
>+     * write to the vq anymore.  Once the guest reads off something,
>+     * we can start queueing things up again.
>+     */
>+    VirtIOSerial *vser;
>+    VirtIOSerialPort *port;
>+    VirtIOSerialPortClass *vsc;
>+
>+    vser = VIRTIO_SERIAL(vdev);
>+    port = find_port_by_vq(vser, vq);
>+    vsc = VIRTIO_SERIAL_PORT_GET_CLASS(port);
>+
>+    if (vsc->guest_writable) {
>+        vsc->guest_writable(port);
>+    }
> }
> 
> static uint32_t get_features(VirtIODevice *vdev, uint32_t features)
>diff --git a/include/hw/virtio/virtio-serial.h b/include/hw/virtio/virtio-serial.h
>index 4746312..3fd696b 100644
>--- a/include/hw/virtio/virtio-serial.h
>+++ b/include/hw/virtio/virtio-serial.h
>@@ -98,6 +98,9 @@ typedef struct VirtIOSerialPortClass {
>         /* Guest is now ready to accept data (virtqueues set up). */
>     void (*guest_ready)(VirtIOSerialPort *port);
> 
>+        /* Guest vq became writable again */
>+    void (*guest_writable)(VirtIOSerialPort *port);
>+
>     /*
>      * Guest wrote some data to the port. This data is handed over to
>      * the app via this callback.  The app can return a size less than
>-- 
>1.9.3
>

Flags:

amit.shah: review? (alevy)

Actions: View | Diff

Attachments on bug 616772: 918736