From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?= Date: Mon, 16 Nov 2020 14:24:56 +0100 Subject: [Intel-wired-lan] [PATCH bpf-next v2 06/10] xsk: propagate napi_id to XDP socket Rx path In-Reply-To: <20201116073848-mutt-send-email-mst@kernel.org> References: <20201116110416.10719-1-bjorn.topel@gmail.com> <20201116110416.10719-7-bjorn.topel@gmail.com> <20201116064953-mutt-send-email-mst@kernel.org> <614a7ce4-2b6b-129b-de7d-71428f7a71f6@intel.com> <20201116073848-mutt-send-email-mst@kernel.org> Message-ID: <585b011f-0817-a684-d1db-125bb55741fe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: intel-wired-lan@osuosl.org List-ID: On 2020-11-16 13:42, Michael S. Tsirkin wrote: > On Mon, Nov 16, 2020 at 01:01:40PM +0100, Bj??rn T??pel wrote: >> >> On 2020-11-16 12:55, Michael S. Tsirkin wrote: >>> On Mon, Nov 16, 2020 at 12:04:12PM +0100, Bj?f??rn T?f??pel wrote: >>>> From: Bj?f??rn T?f??pel >>>> >>>> Add napi_id to the xdp_rxq_info structure, and make sure the XDP >>>> socket pick up the napi_id in the Rx path. The napi_id is used to find >>>> the corresponding NAPI structure for socket busy polling. >>>> >>>> Acked-by: Ilias Apalodimas >>>> Signed-off-by: Bj?f??rn T?f??pel >>> >>> A bunch of drivers just pass in 0. could you explain when >>> is that ok? how bad is it if the wrong id is used? >>> >> >> If zero is passed, which is a non-valid NAPI_ID, busy-polling will never >> be performed. >> >> Depending on the structure of the driver, napi might or might not be >> initialized (napi_id != 0) or even available. When it wasn't obvious, I >> simply set it to zero. >> >> So, short; No harm if zero, but busy-polling cannot be used in an XDP >> context. >> >> >> [...] >>>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c >>>> index 21b71148c532..d71fe41595b7 100644 >>>> --- a/drivers/net/virtio_net.c >>>> +++ b/drivers/net/virtio_net.c >>>> @@ -1485,7 +1485,7 @@ static int virtnet_open(struct net_device *dev) >>>> if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL)) >>>> schedule_delayed_work(&vi->refill, 0); >>>> - err = xdp_rxq_info_reg(&vi->rq[i].xdp_rxq, dev, i); >>>> + err = xdp_rxq_info_reg(&vi->rq[i].xdp_rxq, dev, i, 0); >>>> if (err < 0) >>>> return err; >>> >>> Should this be rq.napi.napi_id ? >>> >> >> Yes, if rq.napi.napi_id is valid here! Is it? > > What initializes it? netif_napi_add? Then I think yes, it's > initialized for all queues ... > Needs to be tested naturally. > Yeah, netid_napi_add does the id generation. My idea was that driver would gradually move to a correct NAPI id (given that it's hard to test w/o HW. Virtio however is simpler to test. :-) Bj?rn