lkml.org 
[lkml]   [2022]   [Jun]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH V6 8/9] virtio: harden vring IRQ
    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@redhat.com> 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@redhat.com> 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@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
    > > > > > Signed-off-by: Jason Wang <jasowang@redhat.com>
    > > > >
    > > > >
    > > > > 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
    > > > >
    > >

    \
     
     \ /
      Last update: 2022-06-13 10:20    [W:4.155 / U:0.088 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site