Missing Stable Patches to HWE Causes Virtio Errors on Google Cloud Platform

Stefan Bader stefan.bader at canonical.com
Mon Apr 24 06:52:20 UTC 2017

On 22.04.2017 15:56, Jason A. Donenfeld wrote:
> Hey Stefan and Thadeu,
> I'm emailing you guys because you seem to be handling the releases of
> the HWE branch of the Ubuntu kernel. You missed two important patches
> for this kernel, which affect its usage on Google Cloud Platform,
> which has now defaulted to using the HWE kernel:

Hi Jason,

thank you for the info. Though you would help us and speed up the whole process by:

- filing a bug report about this on http://launchpad.net. The mos convenient way
  to do this for you (if you have a user there) is to type "ubuntu-bug linux" on
  one of your GKE instances and then put in the additional info about patches.
- usually that should be enough but if you want to increase visibility, send a
  quick email, which points at the report, to kernel-team at lists.ubuntu.com

Having filed a bug report not only allows tracking what and why things go into
the kernel but also allows to notify you once there is a proposed kernel that
includes the changes, so you can verify whether this really helps (and also is
not causing new problems).


> 501db511397fd6efff3aa5b4e8de415b55559550
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=501db511397fd6efff3aa5b4e8de415b55559550
> 6391a4481ba0796805d6581e42f9f0418c099e34
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6391a4481ba0796805d6581e42f9f0418c099e34
> The HWE kernel, and possibly others too, backport some virtio
> improvements related to setting VIRTIO_NET_HDR_F_DATA_VALID on
> received packets so that the CPU doesn't have to checksum packets that
> have already been verified by hardware. In the initial implementation
> of this, the kernel erroneously set this flag too for transmitted
> packets, which is explicitly forbidden by the virtio spec. It was
> rectified by those two commits, but you missed them when doing the
> backporting. Greg KH's 4.9 stable branch got them, but not your
> kernel. While mostly nobody cares about this virtio "correctness"
> issue, it turns out that Google Cloud Platform -- which uses the HWE
> kernel by default -- does care and will silently and mysteriously drop
> packets. This leads to packets being dropped entirely when being
> forwarded between various types of network drivers.
> Could you backport these and do a new release? Users are upset and I'm
> receiving bug reports.
> Thanks,
> Jason

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