Messages in this thread | | | Date | Thu, 30 Jun 2022 13:08:53 +0300 | Subject | Re: [PATCH v1 1/1] virtio: Restore semantics of vq->broken in virtqueues | From | Alexander Atanasov <> |
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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@virtuozzo.com> > > Does > > commit c346dae4f3fbce51bbd4f2ec5e8c6f9b91e93163 > Author: Jason Wang <jasowang@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. Either way if you have a mix of drivers working differently depending on return of the handler it would get really messy.
RR's original intent was to flag a driver as bad why reuse it like that ?
>> 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@linutronix.de> >> Cc: Peter Zijlstra <peterz@infradead.org> >> Cc: "Paul E. McKenney" <paulmck@kernel.org> >> Cc: Marc Zyngier <maz@kernel.org> >> Cc: Halil Pasic <pasic@linux.ibm.com> >> Cc: Cornelia Huck <cohuck@redhat.com> >> Cc: Vineeth Vijayan <vneethv@linux.ibm.com> >> Cc: Peter Oberparleiter <oberpar@linux.ibm.com> >> Cc: linux-s390@vger.kernel.org >> Cc: Xuan Zhuo <xuanzhuo@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
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