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Tsirkin" To: Jason Wang Subject: Re: [PATCH V6 8/9] virtio: harden vring IRQ Message-ID: <20220613041416-mutt-send-email-mst@kernel.org> References: <20220527060120.20964-1-jasowang@redhat.com> <20220527060120.20964-9-jasowang@redhat.com> <20220611010747-mutt-send-email-mst@kernel.org> <20220613023337-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: Peter Oberparleiter , Cindy Lu , "Paul E. McKenney" , linux-s390@vger.kernel.org, Peter Zijlstra , Marc Zyngier , Cornelia Huck , linux-kernel , virtualization , Halil Pasic , eperezma , Vineeth Vijayan , Thomas Gleixner X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" 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 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 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 > > > > > Cc: Peter Zijlstra > > > > > Cc: "Paul E. McKenney" > > > > > Cc: Marc Zyngier > > > > > Cc: Halil Pasic > > > > > Cc: Cornelia Huck > > > > > Cc: Vineeth Vijayan > > > > > Cc: Peter Oberparleiter > > > > > Cc: linux-s390@vger.kernel.org > > > > > Signed-off-by: Jason Wang > > > > > > > > > > > > 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? > > 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? > > > > > > > > > > > > > > > > > > > > > --- > > > > > 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@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization