[dpdk-dev] [PATCH] vfio: support iommu group zero

Stephen Hemminger stephen at networkplumber.org
Wed Dec 9 22:58:01 CET 2015

On Wed, 09 Dec 2015 22:12:33 +0100
Thomas Monjalon <thomas.monjalon at 6wind.com> wrote:

> 2015-12-09 09:55, Stephen Hemminger:
> > The current implementation of VFIO will not with the new no-IOMMU mode
> > in 4.4 kernel. The original code assumed that IOMMU group zero would
> > never be used. Group numbers are assigned starting at zero, and up
> > until now the group numbers came from the hardware which is likely
> > to use group 0 for system devices that are not used with DPDK.
> > 
> > The fix is to allow 0 as a valid group and rearrange code
> > to split the return value from the group value.
> > 
> > Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
> > ---
> > Why was this ignored? It was originally sent on 26 Oct 15 back
> > when IOMMU discussion was lively.
> There was no review of this patch.
> The patch has been marked as deferred recently when it was too late
> to do such feature changes in DPDK code:
> 	http://dpdk.org/dev/patchwork/patch/8035/

This is why as a fallback the MAINTAINER has to review the patch
or direct a sub-maintainer to do it. I think almost 2 months is
plenty of time for review. 

Another alternative policy is to have
a "default yes" policy such that if there are no objections or
discussion things that are submitted early just go in (that
is what ZeroMQ does). http://rfc.zeromq.org/spec:22

* Maintainers SHOULD NOT merge their own patches except in exceptional cases, such as non-responsiveness from other Maintainers for an extended period (more than 1-2 days).

* Maintainers SHALL NOT make value judgments on correct patches.
* Maintainers SHALL merge correct patches from other Contributors rapidly.

* Maintainers SHOULD ask for improvements to incorrect patches and SHOULD reject incorrect patches if the Contributor does not respond constructively.
* Any Contributor who has value judgments on a correct patch SHOULD express these via their own patches.
* Maintainers MAY commit changes to non-source documentation directly to the project.

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