Date:   Thu, 16 Mar 2023 09:06:50 +0000
From:   Martin Habets <habetsm.xilinx@gmail.com>
To:     Jason Wang <jasowang@redhat.com>
Cc:     Gautam Dawar <gautam.dawar@amd.com>, linux-net-drivers@amd.com,
        Edward Cree <ecree.xilinx@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Richard Cochran <richardcochran@gmail.com>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        eperezma@redhat.com, harpreet.anand@amd.com, tanuj.kamde@amd.com,
        koushik.dutta@amd.com
Subject: Re: [PATCH net-next v2 01/14] sfc: add function personality support
 for EF100 devices
Message-ID: <ZBLcKs+IsgJBjqeT@gmail.com>
Mail-Followup-To: Jason Wang <jasowang@redhat.com>,
        Gautam Dawar <gautam.dawar@amd.com>, linux-net-drivers@amd.com,
        Edward Cree <ecree.xilinx@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
        Richard Cochran <richardcochran@gmail.com>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        eperezma@redhat.com, harpreet.anand@amd.com, tanuj.kamde@amd.com,
        koushik.dutta@amd.com
References: <20230307113621.64153-1-gautam.dawar@amd.com>
 <20230307113621.64153-2-gautam.dawar@amd.com>
 <CACGkMEubKv-CGgTdTbt=Ja=pbazXT3nOGY9f_VtRwrOsmf8-rw@mail.gmail.com>
 <ZA8OBEDECFI4grXG@gmail.com>
 <071329fe-7215-235c-06b7-f17bf69d872b@redhat.com>
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On Wed, Mar 15, 2023 at 01:11:23PM +0800, Jason Wang wrote:
> 
> 在 2023/3/13 19:50, Martin Habets 写道:
> > On Fri, Mar 10, 2023 at 01:04:14PM +0800, Jason Wang wrote:
> > > On Tue, Mar 7, 2023 at 7:36 PM Gautam Dawar <gautam.dawar@amd.com> wrote:
> > > > A function personality defines the location and semantics of
> > > > registers in the BAR. EF100 NICs allow different personalities
> > > > of a PCIe function and changing it at run-time. A total of three
> > > > function personalities are defined as of now: EF100, vDPA and
> > > > None with EF100 being the default.
> > > > For now, vDPA net devices can be created on a EF100 virtual
> > > > function and the VF personality will be changed to vDPA in the
> > > > process.
> > > > 
> > > > Co-developed-by: Martin Habets <habetsm.xilinx@gmail.com>
> > > > Signed-off-by: Martin Habets <habetsm.xilinx@gmail.com>
> > > > Signed-off-by: Gautam Dawar <gautam.dawar@amd.com>
> > > > ---
> > > >   drivers/net/ethernet/sfc/ef100.c     |  6 +-
> > > >   drivers/net/ethernet/sfc/ef100_nic.c | 98 +++++++++++++++++++++++++++-
> > > >   drivers/net/ethernet/sfc/ef100_nic.h | 11 ++++
> > > >   3 files changed, 111 insertions(+), 4 deletions(-)
> > > > 
> > > > diff --git a/drivers/net/ethernet/sfc/ef100.c b/drivers/net/ethernet/sfc/ef100.c
> > > > index 71aab3d0480f..c1c69783db7b 100644
> > > > --- a/drivers/net/ethernet/sfc/ef100.c
> > > > +++ b/drivers/net/ethernet/sfc/ef100.c
> > > > @@ -429,8 +429,7 @@ static void ef100_pci_remove(struct pci_dev *pci_dev)
> > > >          if (!efx)
> > > >                  return;
> > > > 
> > > > -       probe_data = container_of(efx, struct efx_probe_data, efx);
> > > > -       ef100_remove_netdev(probe_data);
> > > > +       efx_ef100_set_bar_config(efx, EF100_BAR_CONFIG_NONE);
> > > >   #ifdef CONFIG_SFC_SRIOV
> > > >          efx_fini_struct_tc(efx);
> > > >   #endif
> > > > @@ -443,6 +442,7 @@ static void ef100_pci_remove(struct pci_dev *pci_dev)
> > > >          pci_disable_pcie_error_reporting(pci_dev);
> > > > 
> > > >          pci_set_drvdata(pci_dev, NULL);
> > > > +       probe_data = container_of(efx, struct efx_probe_data, efx);
> > > >          efx_fini_struct(efx);
> > > >          kfree(probe_data);
> > > >   };
> > > > @@ -508,7 +508,7 @@ static int ef100_pci_probe(struct pci_dev *pci_dev,
> > > >                  goto fail;
> > > > 
> > > >          efx->state = STATE_PROBED;
> > > > -       rc = ef100_probe_netdev(probe_data);
> > > > +       rc = efx_ef100_set_bar_config(efx, EF100_BAR_CONFIG_EF100);
> > > >          if (rc)
> > > >                  goto fail;
> > > > 
> > > > diff --git a/drivers/net/ethernet/sfc/ef100_nic.c b/drivers/net/ethernet/sfc/ef100_nic.c
> > > > index 4dc643b0d2db..8cbe5e0f4bdf 100644
> > > > --- a/drivers/net/ethernet/sfc/ef100_nic.c
> > > > +++ b/drivers/net/ethernet/sfc/ef100_nic.c
> > > > @@ -772,6 +772,99 @@ static int efx_ef100_get_base_mport(struct efx_nic *efx)
> > > >          return 0;
> > > >   }
> > > > 
> > > > +/* BAR configuration.
> > > > + * To change BAR configuration, tear down the current configuration (which
> > > > + * leaves the hardware in the PROBED state), and then initialise the new
> > > > + * BAR state.
> > > > + */
> > > > +struct ef100_bar_config_ops {
> > > > +       int (*init)(struct efx_probe_data *probe_data);
> > > > +       void (*fini)(struct efx_probe_data *probe_data);
> > > > +};
> > > > +
> > > > +static const struct ef100_bar_config_ops bar_config_ops[] = {
> > > > +       [EF100_BAR_CONFIG_EF100] = {
> > > > +               .init = ef100_probe_netdev,
> > > > +               .fini = ef100_remove_netdev
> > > > +       },
> > > > +#ifdef CONFIG_SFC_VDPA
> > > > +       [EF100_BAR_CONFIG_VDPA] = {
> > > > +               .init = NULL,
> > > > +               .fini = NULL
> > > > +       },
> > > > +#endif
> > > > +       [EF100_BAR_CONFIG_NONE] = {
> > > > +               .init = NULL,
> > > > +               .fini = NULL
> > > > +       },
> > > > +};
> > > This looks more like a mini bus implementation. I wonder if we can
> > > reuse an auxiliary bus here which is more user friendly for management
> > > tools.
> > When we were in the design phase of vDPA for EF100 it was still called
> > virtbus, and the virtbus discussion was in full swing at that time.
> > We could not afford to add risk to the project by depending on it, as
> > it might not have been merged at all.
> 
> 
> Right.
> 
> 
> > If we were doing the same design now I would definitely consider using
> > the auxiliary bus.
> > 
> > Martin
> 
> 
> But it's not late to do the change now. Auxiliary bus has been used by a lot
> of devices (even with vDPA device). The change looks not too complicated.

I'm surprised you think this would not be complicated. From my view it would
require redesign, redevelopment and retest of vdpa which would take months. That is
assuming we can get some of the resources back.

> This looks more scalable and convenient for management layer.

There is not much difference for the management layer, it uses the vdpa tool now
and it would do so with the auxiliary bus. The difference is that with the
auxiliary bus users would have to load another module for sfc vDPA support.
Are we maybe on 2 different trains of thought here?

Martin