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SubjectRe: [PATCH v2 0/3] vsock/virtio: several fixes in the .probe() and .remove()
On Mon, Jul 01, 2019 at 07:03:57PM +0200, Stefano Garzarella wrote:
> On Mon, Jul 01, 2019 at 04:11:13PM +0100, Stefan Hajnoczi wrote:
> > On Fri, Jun 28, 2019 at 02:36:56PM +0200, Stefano Garzarella wrote:
> > > During the review of "[PATCH] vsock/virtio: Initialize core virtio vsock
> > > before registering the driver", Stefan pointed out some possible issues
> > > in the .probe() and .remove() callbacks of the virtio-vsock driver.
> > >
> > > This series tries to solve these issues:
> > > - Patch 1 adds RCU critical sections to avoid use-after-free of
> > > 'the_virtio_vsock' pointer.
> > > - Patch 2 stops workers before to call vdev->config->reset(vdev) to
> > > be sure that no one is accessing the device.
> > > - Patch 3 moves the works flush at the end of the .remove() to avoid
> > > use-after-free of 'vsock' object.
> > >
> > > v2:
> > > - Patch 1: use RCU to protect 'the_virtio_vsock' pointer
> > > - Patch 2: no changes
> > > - Patch 3: flush works only at the end of .remove()
> > > - Removed patch 4 because virtqueue_detach_unused_buf() returns all the buffers
> > > allocated.
> > >
> > > v1: https://patchwork.kernel.org/cover/10964733/
> >
> > This looks good to me.
>
> Thanks for the review!
>
> >
> > Did you run any stress tests? For example an SMP guest constantly
> > connecting and sending packets together with a script that
> > hotplug/unplugs vhost-vsock-pci from the host side.
>
> Yes, I started an SMP guest (-smp 4 -monitor tcp:127.0.0.1:1234,server,nowait)
> and I run these scripts to stress the .probe()/.remove() path:
>
> - guest
> while true; do
> cat /dev/urandom | nc-vsock -l 4321 > /dev/null &
> cat /dev/urandom | nc-vsock -l 5321 > /dev/null &
> cat /dev/urandom | nc-vsock -l 6321 > /dev/null &
> cat /dev/urandom | nc-vsock -l 7321 > /dev/null &
> wait
> done
>
> - host
> while true; do
> cat /dev/urandom | nc-vsock 3 4321 > /dev/null &
> cat /dev/urandom | nc-vsock 3 5321 > /dev/null &
> cat /dev/urandom | nc-vsock 3 6321 > /dev/null &
> cat /dev/urandom | nc-vsock 3 7321 > /dev/null &
> sleep 2
> echo "device_del v1" | nc 127.0.0.1 1234
> sleep 1
> echo "device_add vhost-vsock-pci,id=v1,guest-cid=3" | nc 127.0.0.1 1234
> sleep 1
> done
>
> Do you think is enough or is better to have a test more accurate?

That's good when left running overnight so that thousands of hotplug
events are tested.

Stefan
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