Jason Wang
2022-Jul-01 01:07 UTC
[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 at virtuozzo.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 at virtuozzo.com> > > > > Does > > > > commit c346dae4f3fbce51bbd4f2ec5e8c6f9b91e93163 > > Author: Jason Wang <jasowang at redhat.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 at redhat.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 at linutronix.de> > >> Cc: Peter Zijlstra <peterz at infradead.org> > >> Cc: "Paul E. McKenney" <paulmck at kernel.org> > >> Cc: Marc Zyngier <maz at kernel.org> > >> Cc: Halil Pasic <pasic at linux.ibm.com> > >> Cc: Cornelia Huck <cohuck at redhat.com> > >> Cc: Vineeth Vijayan <vneethv at linux.ibm.com> > >> Cc: Peter Oberparleiter <oberpar at linux.ibm.com> > >> Cc: linux-s390 at vger.kernel.org > >> Cc: Xuan Zhuo <xuanzhuo at linux.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 >