Re: [PATCH 2/2] virtio: console: add locking around c_ovq operations
From: Asias He <hidden>
Date: 2013-03-29 00:29:01
On Thu, Mar 28, 2013 at 04:58:33PM +0530, Amit Shah wrote:
When multiple ovq operations are being performed (lots of open/close operations on virtio_console fds), the __send_control_msg() function can get confused without locking. A simple recipe to cause badness is: * create a QEMU VM with two virtio-serial ports * in the guest, do while true;do echo abc >/dev/vport0p1;done while true;do echo edf >/dev/vport0p2;done In one run, this caused a panic in __send_control_msg(). In another, I got virtio_console virtio0: control-o:id 0 is not a head! This also results repeated messages similar to these on the host: qemu-kvm: virtio-serial-bus: Unexpected port id 478762112 for device virtio-serial-bus.0 qemu-kvm: virtio-serial-bus: Unexpected port id 478762368 for device virtio-serial-bus.0 Reported-by: FuXiangChun <redacted> Signed-off-by: Amit Shah <redacted>
So, probably this will not apply on virtio-next because of the virtqueue_add_outbuf change. Anyway, Reviewed-by: Asias He [off-list ref]
quoted hunk ↗ jump to hunk
--- drivers/char/virtio_console.c | 5 +++++ 1 file changed, 5 insertions(+)diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index 7e9bc1d..410866c 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c@@ -150,6 +150,7 @@ struct ports_device { /* To protect the vq operations for the control channel */ spinlock_t c_ivq_lock; + spinlock_t c_ovq_lock; /* The current config space is stored here */ struct virtio_console_config config;@@ -569,11 +570,14 @@ static ssize_t __send_control_msg(struct ports_device *portdev, u32 port_id, vq = portdev->c_ovq; sg_init_one(sg, &cpkt, sizeof(cpkt)); + + spin_lock_irq(&portdev->c_ovq_lock); if (virtqueue_add_buf(vq, sg, 1, 0, &cpkt, GFP_ATOMIC) == 0) { virtqueue_kick(vq); while (!virtqueue_get_buf(vq, &len)) cpu_relax(); } + spin_unlock_irq(&portdev->c_ovq_lock); return 0; }@@ -1987,6 +1991,7 @@ static int virtcons_probe(struct virtio_device *vdev) unsigned int nr_added_bufs; spin_lock_init(&portdev->c_ivq_lock); + spin_lock_init(&portdev->c_ovq_lock); INIT_WORK(&portdev->control_work, &control_work_handler); nr_added_bufs = fill_queue(portdev->c_ivq,-- 1.8.1.4 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
-- Asias