On Wed, Jun 15, 2022 at 09:38:18AM +0800, Jason Wang
wrote:> On Tue, Jun 14, 2022 at 11:49 PM Michael S. Tsirkin <mst at
redhat.com> 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 at
redhat.com> 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
at redhat.com> wrote:
> > > > > >
> > > > > > On Mon, Jun 13, 2022 at 4:59 PM Michael S. Tsirkin
<mst at redhat.com> 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 at redhat.com> 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 at 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 at 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 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
> > > > > > > > > > > > > >
Signed-off-by: Jason Wang <jasowang at 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?
> > > > > > > >
> > > > > > > > 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)
Absolutely. Question is do you think we can fix everything by the
release? At least for rpmsg we don't seem to have a handle on it yet.
> 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;
and drop it on reset?
> >
> >
> > > >
> > > >
> > > > > >
> > > > > > >
> > > > > > > > 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
> > > > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > >
> > > > > > >
> > > >
> >