On Fri, Jun 17, 2022 at 1:36 PM Michael S. Tsirkin <mst at redhat.com>
wrote:>
> On Fri, Jun 17, 2022 at 09:24:57AM +0800, Jason Wang wrote:
> > On Fri, Jun 17, 2022 at 1:11 AM Michael S. Tsirkin <mst at
redhat.com> wrote:
> > >
> > > 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?
> >
> > Probably not, I'm auditing all the virtio drivers and it seems we
have
> > many issues:
> >
> > 1) race between subsystem registration/use and virtio_device_ready()
> > 2) race between notifications and subsystem registerstiation/use
> >
> > And it looks to me even virtio-net has this race.
>
> Interesting. How does it look for virtio-net?
Will post a patch soon.
>
> > So I think I will post a patch to disable this like below for this
release.
>
>
> However please do post patches that add device_ready as appropriate.
> This is basic spec compliance.
Working on this.
>
> Also do you think we should do a full revert? Maybe a Kconfig option is
> ok for now.
Yes, Kconfig should be fine.
Patch will be posted soon.
Thanks
>
>
> > > At least for rpmsg we don't seem to have a handle on it yet.
> >
> > Yes.
> >
> > >
> > >
> > > > 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?
> >
> > Right.
> >
> > Thanks
> >
> > >
> > > > >
> > > > >
> > > > > > >
> > > > > > >
> > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > > 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
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > >
> > > > > > >
> > > > >
> > >
>