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Mon, 11 May 2020 04:33:10 -0700 (PDT) From: Paul Durrant X-Google-Original-From: "Paul Durrant" Reply-To: To: "'Denis Kirjanov'" , Cc: , , , References: <1589192541-11686-1-git-send-email-kda@linux-powerpc.org> <1589192541-11686-3-git-send-email-kda@linux-powerpc.org> In-Reply-To: <1589192541-11686-3-git-send-email-kda@linux-powerpc.org> Subject: RE: [PATCH net-next v9 2/2] xen networking: add XDP offset adjustment to xen-netback Date: Mon, 11 May 2020 12:33:08 +0100 Message-ID: <000c01d62787$f2e59a10$d8b0ce30$@xen.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 16.0 Content-Language: en-gb Thread-Index: AQIU9PmTVpNq2fLG8JgzWe5HwULahQDzXzdtqB2JyBA= Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org > -----Original Message----- > From: Denis Kirjanov > Sent: 11 May 2020 11:22 > To: netdev@vger.kernel.org > Cc: brouer@redhat.com; jgross@suse.com; wei.liu@kernel.org; paul@xen.org; ilias.apalodimas@linaro.org > Subject: [PATCH net-next v9 2/2] xen networking: add XDP offset adjustment to xen-netback > > the patch basically adds the offset adjustment and netfront > state reading to make XDP work on netfront side. > > Signed-off-by: Denis Kirjanov > --- > drivers/net/xen-netback/common.h | 2 ++ > drivers/net/xen-netback/netback.c | 7 +++++++ > drivers/net/xen-netback/rx.c | 7 ++++++- > drivers/net/xen-netback/xenbus.c | 28 ++++++++++++++++++++++++++++ > 4 files changed, 43 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h > index 05847eb..4a148d6 100644 > --- a/drivers/net/xen-netback/common.h > +++ b/drivers/net/xen-netback/common.h > @@ -280,6 +280,7 @@ struct xenvif { > u8 ip_csum:1; > u8 ipv6_csum:1; > u8 multicast_control:1; > + u8 xdp_enabled:1; > > /* Is this interface disabled? True when backend discovers > * frontend is rogue. > @@ -395,6 +396,7 @@ static inline pending_ring_idx_t nr_pending_reqs(struct xenvif_queue *queue) > irqreturn_t xenvif_interrupt(int irq, void *dev_id); > > extern bool separate_tx_rx_irq; > +extern bool provides_xdp_headroom; > > extern unsigned int rx_drain_timeout_msecs; > extern unsigned int rx_stall_timeout_msecs; > diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c > index 315dfc6..6dfca72 100644 > --- a/drivers/net/xen-netback/netback.c > +++ b/drivers/net/xen-netback/netback.c > @@ -96,6 +96,13 @@ > module_param_named(hash_cache_size, xenvif_hash_cache_size, uint, 0644); > MODULE_PARM_DESC(hash_cache_size, "Number of flows in the hash cache"); > > +/* The module parameter tells that we have to put data > + * for xen-netfront with the XDP_PACKET_HEADROOM offset > + * needed for XDP processing > + */ > +bool provides_xdp_headroom = true; > +module_param(provides_xdp_headroom, bool, 0644); > + > static void xenvif_idx_release(struct xenvif_queue *queue, u16 pending_idx, > u8 status); > > diff --git a/drivers/net/xen-netback/rx.c b/drivers/net/xen-netback/rx.c > index ef58870..c97c98e 100644 > --- a/drivers/net/xen-netback/rx.c > +++ b/drivers/net/xen-netback/rx.c > @@ -33,6 +33,11 @@ > #include > #include > > +static int xenvif_rx_xdp_offset(struct xenvif *vif) > +{ > + return vif->xdp_enabled ? XDP_PACKET_HEADROOM : 0; > +} > + > static bool xenvif_rx_ring_slots_available(struct xenvif_queue *queue) > { > RING_IDX prod, cons; > @@ -356,7 +361,7 @@ static void xenvif_rx_data_slot(struct xenvif_queue *queue, > struct xen_netif_rx_request *req, > struct xen_netif_rx_response *rsp) > { > - unsigned int offset = 0; > + unsigned int offset = xenvif_rx_xdp_offset(queue->vif); > unsigned int flags; > > do { > diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c > index 286054b..d447191 100644 > --- a/drivers/net/xen-netback/xenbus.c > +++ b/drivers/net/xen-netback/xenbus.c > @@ -393,6 +393,20 @@ static void set_backend_state(struct backend_info *be, > } > } > > +static void read_xenbus_frontend_xdp(struct backend_info *be, > + struct xenbus_device *dev) > +{ > + struct xenvif *vif = be->vif; > + unsigned int val; > + int err; > + > + err = xenbus_scanf(XBT_NIL, dev->otherend, > + "feature-xdp", "%u", &val); > + if (err != 1) > + return; > + vif->xdp_enabled = val; > +} > + > /** > * Callback received when the frontend's state changes. > */ > @@ -417,6 +431,11 @@ static void frontend_changed(struct xenbus_device *dev, > set_backend_state(be, XenbusStateConnected); > break; > > + case XenbusStateReconfiguring: > + read_xenbus_frontend_xdp(be, dev); I think this being the only call to read_xenbus_frontend_xdp() is still a problem. What happens if netback is reloaded against a netfront that has already enabled 'feature-xdp'? AFAICT vif->xdp_enabled would remain false after the reload. Paul > + xenbus_switch_state(dev, XenbusStateReconfigured); > + break; > + > case XenbusStateClosing: > set_backend_state(be, XenbusStateClosing); > break; > @@ -1036,6 +1055,15 @@ static int netback_probe(struct xenbus_device *dev, > goto abort_transaction; > } > > + /* we can adjust a headroom for netfront XDP processing */ > + err = xenbus_printf(xbt, dev->nodename, > + "feature-xdp-headroom", "%d", > + provides_xdp_headroom); > + if (err) { > + message = "writing feature-xdp-headroom"; > + goto abort_transaction; > + } > + > /* We don't support rx-flip path (except old guests who > * don't grok this feature flag). > */ > -- > 1.8.3.1