Re: [dpdk-dev] [PATCH] vhost-user: enable virtio 1.0

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Fri, Oct 16, 2015 at 09:43:09AM +0200, Andriy Berestovskyy wrote:
> Hi guys,
> Just a minor note: ARM is bi-endian in fact.

Thank you for clarifying that my old memory is right :)

	--yliu

> For instance, there are
> both endians tool chains available on Linaro.
> 
> Andriy
> 
> 
> On Fri, Oct 16, 2015 at 8:20 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Fri, Oct 16, 2015 at 10:24:38AM +0800, Yuanhan Liu wrote:
> >> On Thu, Oct 15, 2015 at 04:18:59PM +0300, Michael S. Tsirkin wrote:
> >> > On Thu, Oct 15, 2015 at 02:08:39PM +0300, Marcel Apfelbaum wrote:
> >> > > Make vhost-user virtio 1.0 compatible by adding it to the
> >> > > supported features and keeping the header length
> >> > > the same as for mergeable RX buffers.
> >> > >
> >> > > Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
> >>
> >> Marcel, that's actually one of my TODOs in this quarter. So, thank
> >> you! :)
> >>
> >> >
> >> > Looks good to me
> >> >
> >> > Acked-by: Michael S. Tsirkin <mst@redhat.com>
> >> >
> >> > Just one question: dpdk is only supported on little-endian
> >> > platforms at the moment, right?
> >>
> >> AFAIK, yes. But you might also see that there are some patch to add
> >> ARM arch support showed up in the mailing list few weeks ago.
> >
> > Luckily, that's also little-endian.
> >
> >> > virtio 1 spec requires little endian.
> >>
> >> I made a quick list of the difference between virtio v0.95 and v1.0
> >> months ago just by reading your kernel commits of adding v1.0 support:
> >>
> >>     +-------------------+-----------------+------------------------------+
> >>     |                   |     v0.95       |  v1.0                        |
> >>     +-------------------+-----------------+------------------------------+
> >> 1)  | features bits     |     32          |  64                          |
> >>     +-------------------+-----------------+------------------------------+
> >> 2)  | Endianness        |     nature      |  Little Endian               |
> >>     +-------------------+-----------------+------------------------------+
> >> 3)  | vring space       |     contiguous  |  avail and used buffer could |
> >>     |                   |     memory      |  be on a separate memory     |
> >
> > And desc buffer, too.
> >
> >>     +-------------------+-----------------+------------------------------+
> >> 4)  | FEATURE_OK status |     No          |   Yes                        |
> >>     +-------------------+-----------------+------------------------------+
> >>
> >>
> >>
> >> For 1), I guess we have been using 64 bit for storing features bits
> >> for vhost since long time ago. So, there should be no extra effort.
> >>
> >> For 2), as stated, there might be no issue as far as DPDK is little
> >> endian only. But we'd better add a wrapper for that, as it seems
> >> adding big endian support would come in near future.
> >
> > OK, but it probably doesn't
> >
> >> For 3), are we actually doing that? I just saw that there is a kernel
> >> patch to introduce two functions for getting the avail and used buffer
> >> address, respectively.  But I didn't see that the two buffer are
> >> allocated in non-contiguous memory.
> >
> > That will soon happen, anyone claiming support for virtio 1
> >
> > But vhost user already sends each ring part separately.
> > Does dpdk assume they are contigious?
> >
> >> For 4), it's a work we should do at virtio PMD driver. And it seems
> >> that there are far more work need to be done at virtio PDM driver than
> >> at vhost lib, say, adding the virtio morden PCI support.
> >>
> >> Besides those 4 differs, did I miss anyting?
> >
> >
> > From virtio PMD point of view? There are more
> > differences. The trick is to find "legacy interface"
> > sections and go over them, that compares 0.9 to 1.0.
> >
> >>
> >> BTW, since we already have same TODOs, I guess it'd be better to
> >> share what we have in our TODO list. Here are what I got till the
> >> time writing this email (in order of priority):
> >>
> >> - a vhost performance issue (it might last long; it might not).
> >>
> >> - vhost-user live migration support
> >>
> >> - virtio 1.0 support, including PMD and vhost lib (and you guys have
> >>   already done that :)
> >>
> >> Thanks.
> >
> > This patch only touches the vhost lib, though.
> >
> >>       --yliu
> >>
> >>
> >> > > ---
> >> > >
> >> > > To be applied on top of:
> >> > >    [dpdk-dev] [PATCH v6 00/13] vhost-user multiple queues enabling
> >> > >
> >> > > Thanks,
> >> > > Marcel
> >> > >
> >> > >  lib/librte_vhost/virtio-net.c | 15 ++++++++-------
> >> > >  1 file changed, 8 insertions(+), 7 deletions(-)
> >> > >
> >> > > diff --git a/lib/librte_vhost/virtio-net.c b/lib/librte_vhost/virtio-net.c
> >> > > index a51327d..ee4650e 100644
> >> > > --- a/lib/librte_vhost/virtio-net.c
> >> > > +++ b/lib/librte_vhost/virtio-net.c
> >> > > @@ -75,6 +75,7 @@ static struct virtio_net_config_ll *ll_root;
> >> > >                           (1ULL << VIRTIO_NET_F_CTRL_VQ) | \
> >> > >                           (1ULL << VIRTIO_NET_F_CTRL_RX) | \
> >> > >                           (1ULL << VIRTIO_NET_F_MQ)      | \
> >> > > +                         (1ULL << VIRTIO_F_VERSION_1)   | \
> >> > >                           (1ULL << VHOST_F_LOG_ALL)      | \
> >> > >                           (1ULL << VHOST_USER_F_PROTOCOL_FEATURES))
> >> > >  static uint64_t VHOST_FEATURES = VHOST_SUPPORTED_FEATURES;
> >> > > @@ -477,17 +478,17 @@ set_features(struct vhost_device_ctx ctx, uint64_t *pu)
> >> > >           return -1;
> >> > >
> >> > >   dev->features = *pu;
> >> > > - if (dev->features & (1 << VIRTIO_NET_F_MRG_RXBUF)) {
> >> > > -         LOG_DEBUG(VHOST_CONFIG,
> >> > > -                 "(%"PRIu64") Mergeable RX buffers enabled\n",
> >> > > -                 dev->device_fh);
> >> > > + if (dev->features &
> >> > > +     ((1 << VIRTIO_NET_F_MRG_RXBUF) | (1ULL << VIRTIO_F_VERSION_1))) {
> >> > >           vhost_hlen = sizeof(struct virtio_net_hdr_mrg_rxbuf);
> >> > >   } else {
> >> > > -         LOG_DEBUG(VHOST_CONFIG,
> >> > > -                 "(%"PRIu64") Mergeable RX buffers disabled\n",
> >> > > -                 dev->device_fh);
> >> > >           vhost_hlen = sizeof(struct virtio_net_hdr);
> >> > >   }
> >> > > + LOG_DEBUG(VHOST_CONFIG,
> >> > > +              "(%"PRIu64") Mergeable RX buffers %s, virtio 1 %s\n",
> >> > > +           dev->device_fh,
> >> > > +              (dev->features & (1 << VIRTIO_NET_F_MRG_RXBUF)) ? "on" : "off",
> >> > > +              (dev->features & (1ULL << VIRTIO_F_VERSION_1)) ? "on" : "off");
> >> > >
> >> > >   for (i = 0; i < dev->virt_qp_nb; i++) {
> >> > >           uint16_t base_idx = i * VIRTIO_QNUM;
> >> > > --
> >> > > 2.1.0
> 
> 
> 
> -- 
> Andriy Berestovskyy