lkml.org 
[lkml]   [2011]   [Dec]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH v3 2/3] hvc_init(): Enforce one-time initialization.
On (Tue) 06 Dec 2011 [09:05:38], Miche Baker-Harvey wrote:
> Amit,
>
> Ah, indeed. I am not using MSI-X, so virtio_pci::vp_try_to_find_vqs()
> calls vp_request_intx() and sets up an interrupt callback. From
> there, when an interrupt occurs, the stack looks something like this:
>
> virtio_pci::vp_interrupt()
> virtio_pci::vp_vring_interrupt()
> virtio_ring::vring_interrupt()
> vq->vq.callback() <-- in this case, that's virtio_console::control_intr()
> workqueue::schedule_work()
> workqueue::queue_work()
> queue_work_on(get_cpu()) <-- queues the work on the current CPU.
>
> I'm not doing anything to keep multiple control message from being
> sent concurrently to the guest, and we will take those interrupts on
> any CPU. I've confirmed that the two instances of
> handle_control_message() are occurring on different CPUs.

Hi Miche,

Here's a quick-and-dirty hack that should help. I've not tested this,
and it's not yet signed-off-by. Let me know if this helps.

From 16708fa247c0dd34aa55d78166d65e463f9be6d6 Mon Sep 17 00:00:00 2001
Message-Id: <16708fa247c0dd34aa55d78166d65e463f9be6d6.1324015123.git.amit.shah@redhat.com>
From: Amit Shah <amit.shah@redhat.com>
Date: Fri, 16 Dec 2011 11:27:04 +0530
Subject: [PATCH 1/1] virtio: console: Serialise control work

We currently allow multiple instances of the control work handler to run
in parallel. This isn't expected to work; serialise access by disabling
interrupts on new packets from the Host and enable them when all the
existing ones are consumed.
---
drivers/char/virtio_console.c | 6 ++++++
1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 8e3c46d..72d396c 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1466,6 +1466,7 @@ static void control_work_handler(struct work_struct *work)
portdev = container_of(work, struct ports_device, control_work);
vq = portdev->c_ivq;

+ start:
spin_lock(&portdev->cvq_lock);
while ((buf = virtqueue_get_buf(vq, &len))) {
spin_unlock(&portdev->cvq_lock);
@@ -1483,6 +1484,10 @@ static void control_work_handler(struct work_struct *work)
}
}
spin_unlock(&portdev->cvq_lock);
+ if (unlikely(!virtqueue_enable_cb(vq))) {
+ virtqueue_disable_cb(vq);
+ goto start;
+ }
}

static void out_intr(struct virtqueue *vq)
@@ -1533,6 +1538,7 @@ static void control_intr(struct virtqueue *vq)
{
struct ports_device *portdev;

+ virtqueue_disable_cb(vq);
portdev = vq->vdev->priv;
schedule_work(&portdev->control_work);
}
--
1.7.7.4


Amit


\
 
 \ /
  Last update: 2011-12-16 07:03    [W:0.312 / U:0.676 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site