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Date: Fri, 1 Jul 2022 09:07:21 +0800
From: Jason Wang <jasowang@...hat.com>
To: Alexander Atanasov <alexander.atanasov@...tuozzo.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>, kernel@...nvz.org,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>,
"Paul E. McKenney" <paulmck@...nel.org>,
Marc Zyngier <maz@...nel.org>,
Halil Pasic <pasic@...ux.ibm.com>,
Cornelia Huck <cohuck@...hat.com>,
Vineeth Vijayan <vneethv@...ux.ibm.com>,
Peter Oberparleiter <oberpar@...ux.ibm.com>,
linux-s390@...r.kernel.org, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
virtualization <virtualization@...ts.linux-foundation.org>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/1] virtio: Restore semantics of vq->broken in virtqueues
On Thu, Jun 30, 2022 at 6:09 PM Alexander Atanasov
<alexander.atanasov@...tuozzo.com> wrote:
>
> Hello,
>
> On 30/06/2022 12:46, Michael S. Tsirkin wrote:
> > On Thu, Jun 30, 2022 at 09:36:46AM +0000, Alexander Atanasov wrote:
> >> virtio: harden vring IRQ (8b4ec69d7e09) changed the use
> >> of vq->broken. As result vring_interrupt handles IRQs for
> >> broken drivers as IRQ_NONE and not IRQ_HANDLED and made impossible
> >> to initiallize vqs before the driver is ready, i.e. in probe method.
> >> Balloon driver does this and it can not load because it fails in
> >> vqs_init with -EIO.
> >>
> >> So instead of changing the original intent ot the flag introduce
> >> a new flag vq->ready which servers the purpose to check of early IRQs
> >> and restore the behaviour of the vq->broken flag.
> >>
> >> Signed-off-by: Alexander Atanasov <alexander.atanasov@...tuozzo.com>
> >
> > Does
> >
> > commit c346dae4f3fbce51bbd4f2ec5e8c6f9b91e93163
> > Author: Jason Wang <jasowang@...hat.com>
> > Date: Wed Jun 22 09:29:40 2022 +0800
> >
> > virtio: disable notification hardening by default
> >
> >
> > solve the problem for you?
>
>
> No, it won't if CONFIG_VIRTIO_HARDEN_NOTIFICATION is enabled - balloon
> still won't be able to init vqs.
>
> The problem is in virtqueue_add_split and virtqueue_add_packed - can not
> set driver_ok without queues.
>
> The return value of the vring_interrupt gets different - and iirc
> IRQ_NONE for broken device can lead to interrupt storms - i am not sure
> if that is valid for virtio devices yet but for real harware most
> likely.
Valid but the interrupt will be noted and disabled by the kernel then.
> Either way if you have a mix of drivers working differently
> depending on return of the handler it would get really messy.
Yes, IRQ_HANDLED may break the driver that shares a single IRQ.
>
> RR's original intent was to flag a driver as bad why reuse it like that ?
It's somehow the same, we want to prevent the driver from using the
malicious or buggy device.
Anyhow, I think using a dedicated variable is better.
We are discussing a better approach for hardening the notifications.
But in case, this will be merged:
Acked-by: Jason Wang <jasowang@...hat.com>
Thanks
>
>
> >> drivers/virtio/virtio_ring.c | 20 ++++++++++++++------
> >> include/linux/virtio.h | 2 +-
> >> include/linux/virtio_config.h | 10 +++++-----
> >> 3 files changed, 20 insertions(+), 12 deletions(-)
> >>
> >> Cc: Thomas Gleixner <tglx@...utronix.de>
> >> Cc: Peter Zijlstra <peterz@...radead.org>
> >> Cc: "Paul E. McKenney" <paulmck@...nel.org>
> >> Cc: Marc Zyngier <maz@...nel.org>
> >> Cc: Halil Pasic <pasic@...ux.ibm.com>
> >> Cc: Cornelia Huck <cohuck@...hat.com>
> >> Cc: Vineeth Vijayan <vneethv@...ux.ibm.com>
> >> Cc: Peter Oberparleiter <oberpar@...ux.ibm.com>
> >> Cc: linux-s390@...r.kernel.org
> >> Cc: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> >>
> >>
> >> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> >> index 13a7348cedff..dca3cc774584 100644
> >> --- a/drivers/virtio/virtio_ring.c
> >> +++ b/drivers/virtio/virtio_ring.c
> >> @@ -100,6 +100,9 @@ struct vring_virtqueue {
> >> /* Other side has made a mess, don't try any more. */
> >> bool broken;
> >>
> >> + /* the queue is ready to handle interrupts */
> >> + bool ready;
> >> +
> >> /* Host supports indirect buffers */
> >> bool indirect;
> >>
> >> @@ -1688,7 +1691,8 @@ static struct virtqueue *vring_create_virtqueue_packed(
> >> vq->we_own_ring = true;
> >> vq->notify = notify;
> >> vq->weak_barriers = weak_barriers;
> >> - vq->broken = true;
> >> + vq->broken = false;
> >> + vq->ready = false;
> >> vq->last_used_idx = 0;
> >> vq->event_triggered = false;
> >> vq->num_added = 0;
> >> @@ -2134,7 +2138,10 @@ irqreturn_t vring_interrupt(int irq, void *_vq)
> >> return IRQ_NONE;
> >> }
> >>
> >> - if (unlikely(vq->broken)) {
> >> + if (unlikely(vq->broken))
> >> + return IRQ_HANDLED;
> >> +
> >> + if (unlikely(!vq->ready)) {
> >> dev_warn_once(&vq->vq.vdev->dev,
> >> "virtio vring IRQ raised before DRIVER_OK");
> >> return IRQ_NONE;
> >> @@ -2180,7 +2187,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
> >> vq->we_own_ring = false;
> >> vq->notify = notify;
> >> vq->weak_barriers = weak_barriers;
> >> - vq->broken = true;
> >> + vq->broken = false;
> >> + vq->ready = false;
> >> vq->last_used_idx = 0;
> >> vq->event_triggered = false;
> >> vq->num_added = 0;
> >> @@ -2405,7 +2413,7 @@ EXPORT_SYMBOL_GPL(virtio_break_device);
> >> * (probing and restoring). This function should only be called by the
> >> * core, not directly by the driver.
> >> */
> >> -void __virtio_unbreak_device(struct virtio_device *dev)
> >> +void __virtio_device_ready(struct virtio_device *dev)
> >> {
> >> struct virtqueue *_vq;
> >>
> >> @@ -2414,11 +2422,11 @@ void __virtio_unbreak_device(struct virtio_device *dev)
> >> struct vring_virtqueue *vq = to_vvq(_vq);
> >>
> >> /* Pairs with READ_ONCE() in virtqueue_is_broken(). */
> >> - WRITE_ONCE(vq->broken, false);
> >> + WRITE_ONCE(vq->ready, true);
> >> }
> >> spin_unlock(&dev->vqs_list_lock);
> >> }
> >> -EXPORT_SYMBOL_GPL(__virtio_unbreak_device);
> >> +EXPORT_SYMBOL_GPL(__virtio_device_ready);
> >>
> >> dma_addr_t virtqueue_get_desc_addr(struct virtqueue *_vq)
> >> {
> >> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> >> index d8fdf170637c..538c5959949a 100644
> >> --- a/include/linux/virtio.h
> >> +++ b/include/linux/virtio.h
> >> @@ -131,7 +131,7 @@ void unregister_virtio_device(struct virtio_device *dev);
> >> bool is_virtio_device(struct device *dev);
> >>
> >> void virtio_break_device(struct virtio_device *dev);
> >> -void __virtio_unbreak_device(struct virtio_device *dev);
> >> +void __virtio_device_ready(struct virtio_device *dev);
> >>
> >> void virtio_config_changed(struct virtio_device *dev);
> >> #ifdef CONFIG_PM_SLEEP
> >> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> >> index 49c7c32815f1..35cf1b26e05a 100644
> >> --- a/include/linux/virtio_config.h
> >> +++ b/include/linux/virtio_config.h
> >> @@ -259,21 +259,21 @@ void virtio_device_ready(struct virtio_device *dev)
> >>
> >> /*
> >> * The virtio_synchronize_cbs() makes sure vring_interrupt()
> >> - * will see the driver specific setup if it sees vq->broken
> >> + * will see the driver specific setup if it sees vq->ready
> >> * as false (even if the notifications come before DRIVER_OK).
> >> */
> >> virtio_synchronize_cbs(dev);
> >> - __virtio_unbreak_device(dev);
> >> + __virtio_device_ready(dev);
> >> /*
> >> - * The transport should ensure the visibility of vq->broken
> >> + * The transport should ensure the visibility of vq->ready
> >> * before setting DRIVER_OK. See the comments for the transport
> >> * specific set_status() method.
> >> *
> >> * A well behaved device will only notify a virtqueue after
> >> * DRIVER_OK, this means the device should "see" the coherenct
> >> - * memory write that set vq->broken as false which is done by
> >> + * memory write that set vq->ready as true which is done by
> >> * the driver when it sees DRIVER_OK, then the following
> >> - * driver's vring_interrupt() will see vq->broken as false so
> >> + * driver's vring_interrupt() will see vq->true as true so
> >> * we won't lose any notification.
> >> */
> >> dev->config->set_status(dev, status | VIRTIO_CONFIG_S_DRIVER_OK);
> >> --
> >> 2.25.1
>
> --
> Regards,
> Alexander Atanasov
>
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