On Tue, Jun 14, 2022 at 11:49 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > > On Tue, Jun 14, 2022 at 03:40:21PM +0800, Jason Wang wrote: > > On Mon, Jun 13, 2022 at 5:28 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > > > > > > On Mon, Jun 13, 2022 at 05:14:59PM +0800, Jason Wang wrote: > > > > On Mon, Jun 13, 2022 at 5:08 PM Jason Wang <jasowang@xxxxxxxxxx> wrote: > > > > > > > > > > On Mon, Jun 13, 2022 at 4:59 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > > > > > > > > > > > > On Mon, Jun 13, 2022 at 04:51:08PM +0800, Jason Wang wrote: > > > > > > > On Mon, Jun 13, 2022 at 4:19 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > > > > > > > > > > > > > > > > On Mon, Jun 13, 2022 at 04:07:09PM +0800, Jason Wang wrote: > > > > > > > > > On Mon, Jun 13, 2022 at 3:23 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > > > > > > > > > > > > > > > > > > > > On Mon, Jun 13, 2022 at 01:26:59PM +0800, Jason Wang wrote: > > > > > > > > > > > On Sat, Jun 11, 2022 at 1:12 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > > > > > > > > > > > > > > > > > > > > > > > > On Fri, May 27, 2022 at 02:01:19PM +0800, Jason Wang wrote: > > > > > > > > > > > > > This is a rework on the previous IRQ hardening that is done for > > > > > > > > > > > > > virtio-pci where several drawbacks were found and were reverted: > > > > > > > > > > > > > > > > > > > > > > > > > > 1) try to use IRQF_NO_AUTOEN which is not friendly to affinity managed IRQ > > > > > > > > > > > > > that is used by some device such as virtio-blk > > > > > > > > > > > > > 2) done only for PCI transport > > > > > > > > > > > > > > > > > > > > > > > > > > The vq->broken is re-used in this patch for implementing the IRQ > > > > > > > > > > > > > hardening. The vq->broken is set to true during both initialization > > > > > > > > > > > > > and reset. And the vq->broken is set to false in > > > > > > > > > > > > > virtio_device_ready(). Then vring_interrupt() can check and return > > > > > > > > > > > > > when vq->broken is true. And in this case, switch to return IRQ_NONE > > > > > > > > > > > > > to let the interrupt core aware of such invalid interrupt to prevent > > > > > > > > > > > > > IRQ storm. > > > > > > > > > > > > > > > > > > > > > > > > > > The reason of using a per queue variable instead of a per device one > > > > > > > > > > > > > is that we may need it for per queue reset hardening in the future. > > > > > > > > > > > > > > > > > > > > > > > > > > Note that the hardening is only done for vring interrupt since the > > > > > > > > > > > > > config interrupt hardening is already done in commit 22b7050a024d7 > > > > > > > > > > > > > ("virtio: defer config changed notifications"). But the method that is > > > > > > > > > > > > > used by config interrupt can't be reused by the vring interrupt > > > > > > > > > > > > > handler because it uses spinlock to do the synchronization which is > > > > > > > > > > > > > expensive. > > > > > > > > > > > > > > > > > > > > > > > > > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > > > > > > > > > > > > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > > > > > > > > > > > > > Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx> > > > > > > > > > > > > > Cc: Marc Zyngier <maz@xxxxxxxxxx> > > > > > > > > > > > > > Cc: Halil Pasic <pasic@xxxxxxxxxxxxx> > > > > > > > > > > > > > Cc: Cornelia Huck <cohuck@xxxxxxxxxx> > > > > > > > > > > > > > Cc: Vineeth Vijayan <vneethv@xxxxxxxxxxxxx> > > > > > > > > > > > > > Cc: Peter Oberparleiter <oberpar@xxxxxxxxxxxxx> > > > > > > > > > > > > > Cc: linux-s390@xxxxxxxxxxxxxxx > > > > > > > > > > > > > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Jason, I am really concerned by all the fallout. > > > > > > > > > > > > I propose adding a flag to suppress the hardening - > > > > > > > > > > > > this will be a debugging aid and a work around for > > > > > > > > > > > > users if we find more buggy drivers. > > > > > > > > > > > > > > > > > > > > > > > > suppress_interrupt_hardening ? > > > > > > > > > > > > > > > > > > > > > > I can post a patch but I'm afraid if we disable it by default, it > > > > > > > > > > > won't be used by the users so there's no way for us to receive the bug > > > > > > > > > > > report. Or we need a plan to enable it by default. > > > > > > > > > > > > > > > > > > > > > > It's rc2, how about waiting for 1 and 2 rc? Or it looks better if we > > > > > > > > > > > simply warn instead of disable it by default. > > > > > > > > > > > > > > > > > > > > > > Thanks > > > > > > > > > > > > > > > > > > > > I meant more like a flag in struct virtio_driver. > > > > > > > > > > For now, could you audit all drivers which don't call _ready? > > > > > > > > > > I found 5 of these: > > > > > > > > > > > > > > > > > > > > drivers/bluetooth/virtio_bt.c > > > > > > > > > > > > > > > > > > This driver seems to be fine, it doesn't use the device/vq in its probe(). > > > > > > > > > > > > > > > > > > > > > > > > But it calls hci_register_dev and that in turn queues all kind of > > > > > > > > work. Also, can linux start using the device immediately after > > > > > > > > it's registered? > > > > > > > > > > > > > > So I think the driver is allowed to queue before DRIVER_OK. > > > > > > > > > > > > it's not allowed to kick > > > > > > > > > > Yes. > > > > > > > > > > > > > > > > > > If yes, > > > > > > > the only side effect is the delay of the tx interrupt after DRIVER_OK > > > > > > > for a well behaved device. > > > > > > > > > > > > your patches drop the interrupt though, it won't be just delayed. > > > > > > > > > > For a well behaved device, it can only trigger the interrupt after DRIVER_OK. > > > > > > > > > > So for virtio bt, it works like: > > > > > > > > > > 1) driver queue buffer and kick > > > > > 2) driver set DRIVER_OK > > > > > 3) device start to process the buffer > > > > > 4) device send an notification > > > > > > > > > > The only risk is that the virtqueue could be filled before DRIVER_OK, > > > > > or anything I missed? > > > > > > > > btw, hci has an open and close method and we do rx refill in > > > > hdev->open, so we're probably fine here. > > > > > > > > Thanks > > > > > > > > > Sounds good. Now to audit the rest of them from this POV ;) > > > > Adding maintainers. > > > > > > > > drivers/i2c/busses/i2c-virtio.c > > > > It looks to me the device could be used immediately after > > i2c_add_adapter() return. So we probably need to add > > virtio_device_ready() before that. Fortunately, there's no rx vq in > > i2c and the callback looks safe if the callback is called before the > > i2c registration and after virtio_device_ready(). > > > > > drivers/net/caif/caif_virtio.c > > > > A networking device, RX is backed by vringh so we don't need to > > refill. TX is backed by virtio and is available until ndo_open. So > > it's fine to let the core to set DRIVER_OK after probe(). > > > > > drivers/nvdimm/virtio_pmem.c > > > > It doesn't use interrupt so far, so it has nothing to do with the IRQ hardening. > > > > But the device could be used by the subsystem immediately after > > nvdimm_pmem_region_create(), this means the flush could be issued > > before DRIVER_OK. We need virtio_device_ready() before. We don't have > > a RX virtqueue and the callback looks safe if the callback is called > > after virtio_device_ready() but before the nvdimm region creating. > > > > And it looks to me there's a race between the assignment of > > provider_data and virtio_pmem_flush(). If the flush was issued before > > the assignment we will end up with a NULL pointer dereference. This is > > something we need to fix. > > > > > arm_scmi > > > > It looks to me the singleton device could be used by SCMI immediately after > > > > /* Ensure initialized scmi_vdev is visible */ > > smp_store_mb(scmi_vdev, vdev); > > > > So we probably need to do virtio_device_ready() before that. It has an > > optional rx queue but the filling is done after the above assignment, > > so it's safe. And the callback looks safe is a callback is triggered > > after virtio_device_ready() buy before the above assignment. > > > > > virtio_rpmsg_bus.c > > > > > > > This is somehow more complicated. It has an rx queue, the rx filling > > is done before virtio_device_ready() but the kick is done after. And > > it looks to me the device could be used by subsystem immediately > > rpmsg_virtio_add_ctrl_dev() returns. > > > > This means, if we do virtio_device_ready() after > > rpmsg_virtio_add_ctrl_dev(), we may get kick before DRIVER_OK. If we > > do virtio_device_ready() before rpmsg_virtio_add_ctrl_dev(), there's a > > race between the callbacks and rpmsg_virtio_add_ctrl_dev() that could > > be exploited. > > > > It requires more thoughts. > > > > Thanks > > I think at this point let's do it before so we at least do not > get a regression with your patches, add a big comment and work > on fixing properly in the next Linux version. Do you think you can > commit to a full fix in the next linux version? I think it should be ok. If I understand you correctly, you meant to disable the hardening in this release? (Actually, my understanding is that since we are developing mainline instead of a downstream version with a hardening features, bug reports are somehow expected, especially consider most of the bugs are not related to hardening itself) Thanks diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 13a7348cedff..7ef3115efbad 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -1688,7 +1688,7 @@ 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->last_used_idx = 0; vq->event_triggered = false; vq->num_added = 0; > > > > > > > > > > > > > > > > > > > > > > > > > > If not, we need to clarify it in the spec > > > > > > > and call virtio_device_ready() before subsystem registration. > > > > > > > > > > > > hmm, i don't get what we need to clarify > > > > > > > > > > E.g the driver is not allowed to kick or after DRIVER_OK should the > > > > > device only process the buffer after a kick after DRIVER_OK (I think > > > > > no)? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > drivers/gpu/drm/virtio/virtgpu_drv.c > > > > > > > > > > > > > > > > > > It calles virtio_device_ready() in virtio_gpu_init(), and it looks to > > > > > > > > > me the code is correct. > > > > > > > > > > > > > > > > OK. > > > > > > > > > > > > > > > > > > drivers/i2c/busses/i2c-virtio.c > > > > > > > > > > drivers/net/caif/caif_virtio.c > > > > > > > > > > drivers/nvdimm/virtio_pmem.c > > > > > > > > > > > > > > > > > > The above looks fine and we have three more: > > > > > > > > > > > > > > > > > > arm_scmi: probe() doesn't use vq > > > > > > > > > mac80211_hwsim.c: doesn't use vq (only fill rx), but it kicks the rx, > > > > > > > > > it looks to me we need a device_ready before the kick. > > > > > > > > > virtio_rpmsg_bus.c: doesn't use vq > > > > > > > > > > > > > > > > > > I will post a patch for mac80211_hwsim.c. > > > > > > > > > Thanks > > > > > > > > > > > > > > > > Same comments for all of the above. Might linux not start using the > > > > > > > > device once it's registered? > > > > > > > > > > > > > > It depends on the specific subsystem. > > > > > > > > > > > > > > For the subsystem that can't use the device immediately, calling > > > > > > > virtio_device_ready() after the subsystem's registration should be > > > > > > > fine. E.g for the networking subsystem, the TX won't happen if > > > > > > > ndo_open() is not called, calling virtio_device_ready() after > > > > > > > netdev_register() seems to be fine. > > > > > > > > > > > > exactly > > > > > > > > > > > > > For the subsystem that can use the device immediately, if the > > > > > > > subsystem does not depend on the result of a request in the probe to > > > > > > > proceed, we are still fine. Since those requests will be proceed after > > > > > > > DRIVER_OK. > > > > > > > > > > > > Well first won't driver code normally kick as well? > > > > > > > > > > Kick itself is not blocked. > > > > > > > > > > > And without kick, won't everything just be blocked? > > > > > > > > > > It depends on the subsystem. E.g driver can choose to use a callback > > > > > instead of polling the used buffer in the probe. > > > > > > > > > > > > > > > > > > > > > > > > For the rest we need to do virtio_device_ready() before registration. > > > > > > > > > > > > > > Thanks > > > > > > > > > > > > Then we can get an interrupt for an unregistered device. > > > > > > > > > > It depends on the device. For the device that doesn't have an rx queue > > > > > (or device to driver queue), we are fine: > > > > > > > > > > E.g in virtio-blk: > > > > > > > > > > virtio_device_ready(vdev); > > > > > > > > > > err = device_add_disk(&vdev->dev, vblk->disk, virtblk_attr_groups); > > > > > if (err) > > > > > goto out_cleanup_disk; > > > > > > > > > > Thanks > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > --- > > > > > > > > > > > > > drivers/s390/virtio/virtio_ccw.c | 4 ++++ > > > > > > > > > > > > > drivers/virtio/virtio.c | 15 ++++++++++++--- > > > > > > > > > > > > > drivers/virtio/virtio_mmio.c | 5 +++++ > > > > > > > > > > > > > drivers/virtio/virtio_pci_modern_dev.c | 5 +++++ > > > > > > > > > > > > > drivers/virtio/virtio_ring.c | 11 +++++++---- > > > > > > > > > > > > > include/linux/virtio_config.h | 20 ++++++++++++++++++++ > > > > > > > > > > > > > 6 files changed, 53 insertions(+), 7 deletions(-) > > > > > > > > > > > > > > > > > > > > > > > > > > diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c > > > > > > > > > > > > > index c188e4f20ca3..97e51c34e6cf 100644 > > > > > > > > > > > > > --- a/drivers/s390/virtio/virtio_ccw.c > > > > > > > > > > > > > +++ b/drivers/s390/virtio/virtio_ccw.c > > > > > > > > > > > > > @@ -971,6 +971,10 @@ static void virtio_ccw_set_status(struct virtio_device *vdev, u8 status) > > > > > > > > > > > > > ccw->flags = 0; > > > > > > > > > > > > > ccw->count = sizeof(status); > > > > > > > > > > > > > ccw->cda = (__u32)(unsigned long)&vcdev->dma_area->status; > > > > > > > > > > > > > + /* We use ssch for setting the status which is a serializing > > > > > > > > > > > > > + * instruction that guarantees the memory writes have > > > > > > > > > > > > > + * completed before ssch. > > > > > > > > > > > > > + */ > > > > > > > > > > > > > ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_STATUS); > > > > > > > > > > > > > /* Write failed? We assume status is unchanged. */ > > > > > > > > > > > > > if (ret) > > > > > > > > > > > > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > > > > > > > > > > > > > index aa1eb5132767..95fac4c97c8b 100644 > > > > > > > > > > > > > --- a/drivers/virtio/virtio.c > > > > > > > > > > > > > +++ b/drivers/virtio/virtio.c > > > > > > > > > > > > > @@ -220,6 +220,15 @@ static int virtio_features_ok(struct virtio_device *dev) > > > > > > > > > > > > > * */ > > > > > > > > > > > > > void virtio_reset_device(struct virtio_device *dev) > > > > > > > > > > > > > { > > > > > > > > > > > > > + /* > > > > > > > > > > > > > + * The below virtio_synchronize_cbs() guarantees that any > > > > > > > > > > > > > + * interrupt for this line arriving after > > > > > > > > > > > > > + * virtio_synchronize_vqs() has completed is guaranteed to see > > > > > > > > > > > > > + * vq->broken as true. > > > > > > > > > > > > > + */ > > > > > > > > > > > > > + virtio_break_device(dev); > > > > > > > > > > > > > > > > > > > > > > > > So make this conditional > > > > > > > > > > > > > > > > > > > > > > > > > + virtio_synchronize_cbs(dev); > > > > > > > > > > > > > + > > > > > > > > > > > > > dev->config->reset(dev); > > > > > > > > > > > > > } > > > > > > > > > > > > > EXPORT_SYMBOL_GPL(virtio_reset_device); > > > > > > > > > > > > > @@ -428,6 +437,9 @@ int register_virtio_device(struct virtio_device *dev) > > > > > > > > > > > > > dev->config_enabled = false; > > > > > > > > > > > > > dev->config_change_pending = false; > > > > > > > > > > > > > > > > > > > > > > > > > > + INIT_LIST_HEAD(&dev->vqs); > > > > > > > > > > > > > + spin_lock_init(&dev->vqs_list_lock); > > > > > > > > > > > > > + > > > > > > > > > > > > > /* We always start by resetting the device, in case a previous > > > > > > > > > > > > > * driver messed it up. This also tests that code path a little. */ > > > > > > > > > > > > > virtio_reset_device(dev); > > > > > > > > > > > > > @@ -435,9 +447,6 @@ int register_virtio_device(struct virtio_device *dev) > > > > > > > > > > > > > /* Acknowledge that we've seen the device. */ > > > > > > > > > > > > > virtio_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE); > > > > > > > > > > > > > > > > > > > > > > > > > > - INIT_LIST_HEAD(&dev->vqs); > > > > > > > > > > > > > - spin_lock_init(&dev->vqs_list_lock); > > > > > > > > > > > > > - > > > > > > > > > > > > > /* > > > > > > > > > > > > > * device_add() causes the bus infrastructure to look for a matching > > > > > > > > > > > > > * driver. > > > > > > > > > > > > > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c > > > > > > > > > > > > > index c9699a59f93c..f9a36bc7ac27 100644 > > > > > > > > > > > > > --- a/drivers/virtio/virtio_mmio.c > > > > > > > > > > > > > +++ b/drivers/virtio/virtio_mmio.c > > > > > > > > > > > > > @@ -253,6 +253,11 @@ static void vm_set_status(struct virtio_device *vdev, u8 status) > > > > > > > > > > > > > /* We should never be setting status to 0. */ > > > > > > > > > > > > > BUG_ON(status == 0); > > > > > > > > > > > > > > > > > > > > > > > > > > + /* > > > > > > > > > > > > > + * Per memory-barriers.txt, wmb() is not needed to guarantee > > > > > > > > > > > > > + * that the the cache coherent memory writes have completed > > > > > > > > > > > > > + * before writing to the MMIO region. > > > > > > > > > > > > > + */ > > > > > > > > > > > > > writel(status, vm_dev->base + VIRTIO_MMIO_STATUS); > > > > > > > > > > > > > } > > > > > > > > > > > > > > > > > > > > > > > > > > diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c > > > > > > > > > > > > > index 4093f9cca7a6..a0fa14f28a7f 100644 > > > > > > > > > > > > > --- a/drivers/virtio/virtio_pci_modern_dev.c > > > > > > > > > > > > > +++ b/drivers/virtio/virtio_pci_modern_dev.c > > > > > > > > > > > > > @@ -467,6 +467,11 @@ void vp_modern_set_status(struct virtio_pci_modern_device *mdev, > > > > > > > > > > > > > { > > > > > > > > > > > > > struct virtio_pci_common_cfg __iomem *cfg = mdev->common; > > > > > > > > > > > > > > > > > > > > > > > > > > + /* > > > > > > > > > > > > > + * Per memory-barriers.txt, wmb() is not needed to guarantee > > > > > > > > > > > > > + * that the the cache coherent memory writes have completed > > > > > > > > > > > > > + * before writing to the MMIO region. > > > > > > > > > > > > > + */ > > > > > > > > > > > > > vp_iowrite8(status, &cfg->device_status); > > > > > > > > > > > > > } > > > > > > > > > > > > > EXPORT_SYMBOL_GPL(vp_modern_set_status); > > > > > > > > > > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > > > > > > > > > > > > index 9c231e1fded7..13a7348cedff 100644 > > > > > > > > > > > > > --- a/drivers/virtio/virtio_ring.c > > > > > > > > > > > > > +++ b/drivers/virtio/virtio_ring.c > > > > > > > > > > > > > @@ -1688,7 +1688,7 @@ static struct virtqueue *vring_create_virtqueue_packed( > > > > > > > > > > > > > vq->we_own_ring = true; > > > > > > > > > > > > > vq->notify = notify; > > > > > > > > > > > > > vq->weak_barriers = weak_barriers; > > > > > > > > > > > > > - vq->broken = false; > > > > > > > > > > > > > + vq->broken = true; > > > > > > > > > > > > > vq->last_used_idx = 0; > > > > > > > > > > > > > vq->event_triggered = false; > > > > > > > > > > > > > vq->num_added = 0; > > > > > > > > > > > > > > > > > > > > > > > > and make this conditional > > > > > > > > > > > > > > > > > > > > > > > > > @@ -2134,8 +2134,11 @@ irqreturn_t vring_interrupt(int irq, void *_vq) > > > > > > > > > > > > > return IRQ_NONE; > > > > > > > > > > > > > } > > > > > > > > > > > > > > > > > > > > > > > > > > - if (unlikely(vq->broken)) > > > > > > > > > > > > > - return IRQ_HANDLED; > > > > > > > > > > > > > + if (unlikely(vq->broken)) { > > > > > > > > > > > > > + dev_warn_once(&vq->vq.vdev->dev, > > > > > > > > > > > > > + "virtio vring IRQ raised before DRIVER_OK"); > > > > > > > > > > > > > + return IRQ_NONE; > > > > > > > > > > > > > + } > > > > > > > > > > > > > > > > > > > > > > > > > > /* Just a hint for performance: so it's ok that this can be racy! */ > > > > > > > > > > > > > if (vq->event) > > > > > > > > > > > > > @@ -2177,7 +2180,7 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, > > > > > > > > > > > > > vq->we_own_ring = false; > > > > > > > > > > > > > vq->notify = notify; > > > > > > > > > > > > > vq->weak_barriers = weak_barriers; > > > > > > > > > > > > > - vq->broken = false; > > > > > > > > > > > > > + vq->broken = true; > > > > > > > > > > > > > vq->last_used_idx = 0; > > > > > > > > > > > > > vq->event_triggered = false; > > > > > > > > > > > > > vq->num_added = 0; > > > > > > > > > > > > > > > > > > > > > > > > and make this conditional > > > > > > > > > > > > > > > > > > > > > > > > > diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h > > > > > > > > > > > > > index 25be018810a7..d4edfd7d91bb 100644 > > > > > > > > > > > > > --- a/include/linux/virtio_config.h > > > > > > > > > > > > > +++ b/include/linux/virtio_config.h > > > > > > > > > > > > > @@ -256,6 +256,26 @@ void virtio_device_ready(struct virtio_device *dev) > > > > > > > > > > > > > unsigned status = dev->config->get_status(dev); > > > > > > > > > > > > > > > > > > > > > > > > > > BUG_ON(status & VIRTIO_CONFIG_S_DRIVER_OK); > > > > > > > > > > > > > + > > > > > > > > > > > > > + /* > > > > > > > > > > > > > + * The virtio_synchronize_cbs() makes sure vring_interrupt() > > > > > > > > > > > > > + * will see the driver specific setup if it sees vq->broken > > > > > > > > > > > > > + * as false (even if the notifications come before DRIVER_OK). > > > > > > > > > > > > > + */ > > > > > > > > > > > > > + virtio_synchronize_cbs(dev); > > > > > > > > > > > > > + __virtio_unbreak_device(dev); > > > > > > > > > > > > > + /* > > > > > > > > > > > > > + * The transport should ensure the visibility of vq->broken > > > > > > > > > > > > > + * 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 > > > > > > > > > > > > > + * the driver when it sees DRIVER_OK, then the following > > > > > > > > > > > > > + * driver's vring_interrupt() will see vq->broken as false so > > > > > > > > > > > > > + * we won't lose any notification. > > > > > > > > > > > > > + */ > > > > > > > > > > > > > dev->config->set_status(dev, status | VIRTIO_CONFIG_S_DRIVER_OK); > > > > > > > > > > > > > } > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > > > > > > 2.25.1 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization