Re: [dpdk-dev] [ovs-dev] [PATCH v2 0/4] rhel/fedora: non-root OvS out of the box

[Aaron Conole <aconole@redhat.com>]

Aaron Conole <aconole@redhat.com> writes:

> Aaron Conole <aconole@redhat.com> writes:
>
>> This series attempts to introduce the ability to start and use
>> Open vSwitch 'out of the box' as a non-root user.  It does this by
>> modifying the service files to pass the recently introduced --ovs-user
>> argument around, and by making some minor tweaks to the passwd, group,
>> and filesystem information.
>>
>> I prefixed the packaging work with 'redhat', but if rpm or packaging
>> is a preferred prefx for that work, I can respin.
>>
>> The more controversial changes are:
>>
>> * This modifies the /etc/sysconfig/ file on install.
>> * The dpdk support directly modifies /dev/hugepages with a call to chmod
>> * A new user 'openvswitch', and up to two new groups 'openvswitch', and
>>   'hugetlbfs' are created
>> * A change to soexpand.pl to allow conditional inclusion of dpdk-related
>>   options
>>
>
> An interesting development has occurred while testing this series.
>
> It seems that as part of a rowhammer mitigation, access to
> /proc/self/pagemap ends up being restricted.  This makes DPDK break in a
> catastrophic way.
>
> One way of mitigating this is to keep the CAP_SYS_ADMIN capability when
> DPDK is enabled (not sure whether it would be a runtime or compile
> time change).  This means we end up keeping many root-user level
> permissions that we probably shouldn't need or want.  I was thinking
> that when DPDK is compiled in, we would keep the CAP_SYS_ADMIN for the
> first iteration of DB synchronization, and then drop it after calling
> DPDK-init.  That would prevent lazy loading, or being able to turn it
> on without restarting the daemon (which I don't like).
>
> Another is to say that if DPDK is enabled at compile time, just don't
> drop permissions at all.  That approach seems really wrong, but it's a
> possibility.
>
> Not sure what else can be done from the OvS side for this.  I think it
> could be possible to do something where before dropping privs, we cache
> the pagemap and then feed it to DPDK during initialization, but that
> will require work from DPDK side, and I'm not sure if it actually works
> with DPDK (because I haven't looked into why the pagemap is being read
> to begin with).
>
> So, I'm a bit stuck on this work, and asking for some opinions.
>

UPDATE: it seems that with DPDK 17.02+, this has been resolved.  I'll
wait for resubmit until after the following commit has been applied:

https://mail.openvswitch.org/pipermail/ovs-dev/2017-July/334893.html