From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A977C433EF for ; Fri, 27 May 2022 07:49:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348092AbiE0Htn (ORCPT ); Fri, 27 May 2022 03:49:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41800 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229510AbiE0Hti (ORCPT ); Fri, 27 May 2022 03:49:38 -0400 Received: from out30-54.freemail.mail.aliyun.com (out30-54.freemail.mail.aliyun.com [115.124.30.54]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D6B3EF6891; Fri, 27 May 2022 00:49:34 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R681e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=xuanzhuo@linux.alibaba.com;NM=1;PH=DS;RN=16;SR=0;TI=SMTPD_---0VEW9I73_1653637770; Received: from localhost(mailfrom:xuanzhuo@linux.alibaba.com fp:SMTPD_---0VEW9I73_1653637770) by smtp.aliyun-inc.com(127.0.0.1); Fri, 27 May 2022 15:49:31 +0800 Message-ID: <1653637760.5957363-7-xuanzhuo@linux.alibaba.com> Subject: Re: [PATCH V6 8/9] virtio: harden vring IRQ Date: Fri, 27 May 2022 15:49:20 +0800 From: Xuan Zhuo To: Jason Wang Cc: tglx@linutronix.de, peterz@infradead.org, paulmck@kernel.org, maz@kernel.org, pasic@linux.ibm.com, cohuck@redhat.com, eperezma@redhat.com, lulu@redhat.com, sgarzare@redhat.com, Vineeth Vijayan , Peter Oberparleiter , linux-s390@vger.kernel.org, mst@redhat.com, jasowang@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <20220527060120.20964-1-jasowang@redhat.com> <20220527060120.20964-9-jasowang@redhat.com> In-Reply-To: <20220527060120.20964-9-jasowang@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 27 May 2022 14:01:19 +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 Reviewed-by: Xuan Zhuo > --- > 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); > + 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; > @@ -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; > 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 >