Michael S. Tsirkin
2022-Jun-30 15:43 UTC
[PATCH v1 1/1] virtio: Restore semantics of vq->broken in virtqueues
On Thu, Jun 30, 2022 at 01:08:53PM +0300, Alexander Atanasov 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.Yea I intend to make CONFIG_VIRTIO_HARDEN_NOTIFICATION depend on BROKEN for now.> 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.No, I think it's the reverse. With IRQ_HANDLED an interrupt storm will keep overloading the CPU since driver tells kernel all is well. With IRQ_NONE kernel will eventually intervene and disable the irq.> 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 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
Jason Wang
2022-Jul-01 01:12 UTC
[PATCH v1 1/1] virtio: Restore semantics of vq->broken in virtqueues
On Thu, Jun 30, 2022 at 11:44 PM Michael S. Tsirkin <mst at redhat.com> wrote:> > On Thu, Jun 30, 2022 at 01:08:53PM +0300, Alexander Atanasov 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. > > Yea I intend to make CONFIG_VIRTIO_HARDEN_NOTIFICATION > depend on BROKEN for now. > > > 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. > > No, I think it's the reverse. With IRQ_HANDLED an interrupt > storm will keep overloading the CPU since driver tells > kernel all is well. With IRQ_NONE kernel will eventually > intervene and disable the irq.Yes, and users may get a warn. For IRQ_HANDLED, it has an issue when the driver is sharing IRQ with other drivers. Thanks> > > 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 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 >