Re: [dpdk-dev] [PATCH 2/2] net/virtio: do not require IO permissions

[David Marchand <david.marchand@redhat.com>]

On Fri, Oct 18, 2019 at 10:19 AM Tiwei Bie <tiwei.bie@intel.com> wrote:
>
> On Thu, Oct 17, 2019 at 01:56:28PM +0200, David Marchand wrote:
> > On x86, iopl permissions are only needed when the virtio devices are
> > bound to a uio kernel module.
> >
> > When running a dpdk application as non root, the virtio driver was
> > refusing to register because of this check while it could work when
> > binding the device to vfio (requires to have a vIOMMU configured).
> >
> > We still need to call rte_eal_iopl_init() in the constructor so that
> > the interrupt thread would inherit this permission in the case it could
> > be used with UIO later.
> > Log a warning message for the user to understand what is wrong.
> >
> > Signed-off-by: David Marchand <david.marchand@redhat.com>
> > ---
> >  drivers/net/virtio/virtio_ethdev.c | 8 ++------
> >  1 file changed, 2 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
> > index 7261109..3506ca0 100644
> > --- a/drivers/net/virtio/virtio_ethdev.c
> > +++ b/drivers/net/virtio/virtio_ethdev.c
> > @@ -1995,11 +1995,6 @@ exit:
> >  static int eth_virtio_pci_probe(struct rte_pci_driver *pci_drv __rte_unused,
> >       struct rte_pci_device *pci_dev)
> >  {
> > -     if (rte_eal_iopl_init() != 0) {
> > -             PMD_INIT_LOG(ERR, "IOPL call failed - cannot use virtio PMD");
> > -             return 1;
> > -     }
> > -
> >       /* virtio pmd skips probe if device needs to work in vdpa mode */
> >       if (vdpa_mode_selected(pci_dev->device.devargs))
> >               return 1;
> > @@ -2031,7 +2026,8 @@ static struct rte_pci_driver rte_virtio_pmd = {
> >
> >  RTE_INIT(rte_virtio_pmd_init)
> >  {
> > -     rte_eal_iopl_init();
> > +     if (rte_eal_iopl_init() != 0)
> > +             PMD_INIT_LOG(WARNING, "IOPL call failed - virtio devices won't be functional if bound to UIO drivers");
>
> Basically this will undo what below commit did, i.e.
> annoying log will show again.
>
> https://github.com/DPDK/dpdk/commit/705dced4a72a1053368c84c4b68f04f028a78b30

Yes.. true.
I wanted to keep a trace for debug, so maybe lower this to debug
level, or just drop this message.


>
> Maybe it's better to print this error when we really
> need the port IO (legacy device):

virtio calls rte_pci_ioport_map, so I suppose we can change the log
level to ERR in the first patch of this series:
http://patchwork.dpdk.org/patch/61370/

And I suppose I could add some context in this log, like the device name.

>
> https://github.com/DPDK/dpdk/blob/31b798a6f08e9b333b94b8bb26910209aa810b73/drivers/net/virtio/virtio_pci.c#L679-L680
> https://github.com/DPDK/dpdk/blob/31b798a6f08e9b333b94b8bb26910209aa810b73/drivers/net/virtio/virtio_ethdev.c#L1834-L1835


-- 
David Marchand