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Thu, 23 Jan 2020 17:44:53 +0000 From: Haiyang Zhang To: Jakub Kicinski CC: "sashal@kernel.org" , "linux-hyperv@vger.kernel.org" , "netdev@vger.kernel.org" , KY Srinivasan , Stephen Hemminger , "olaf@aepfle.de" , vkuznets , "davem@davemloft.net" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH V3,net-next, 1/2] hv_netvsc: Add XDP support Thread-Topic: [PATCH V3,net-next, 1/2] hv_netvsc: Add XDP support Thread-Index: AQHV0UjdH1AVu+KRP0+E0p14Je7IQaf4ekYAgAABksCAAAcfgIAAAh5w Date: Thu, 23 Jan 2020 17:44:52 +0000 Message-ID: References: <1579713814-36061-1-git-send-email-haiyangz@microsoft.com> <1579713814-36061-2-git-send-email-haiyangz@microsoft.com> <20200123085906.20608707@cakuba> <20200123093013.53d78485@cakuba> In-Reply-To: <20200123093013.53d78485@cakuba> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: msip_labels: MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Enabled=True; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SiteId=72f988bf-86f1-41af-91ab-2d7cd011db47; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: a6ab1373-e798-478b-e5a1-08d7a02bf3ce X-MS-Exchange-CrossTenant-originalarrivaltime: 23 Jan 2020 17:44:52.8696 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: v+blLINXE1BiQT62jxYFEucNvFV7itQRi/GTX3VwRhKxVJ2JW77Ci7teocgBHaaUdUWcuQy4hQfcrW5rNDbo4A== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR21MB1216 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > -----Original Message----- > From: Jakub Kicinski > Sent: Thursday, January 23, 2020 12:30 PM > To: Haiyang Zhang > Cc: sashal@kernel.org; linux-hyperv@vger.kernel.org; netdev@vger.kernel.o= rg; > KY Srinivasan ; Stephen Hemminger > ; olaf@aepfle.de; vkuznets > ; davem@davemloft.net; linux-kernel@vger.kernel.org > Subject: Re: [PATCH V3,net-next, 1/2] hv_netvsc: Add XDP support >=20 > On Thu, 23 Jan 2020 17:14:06 +0000, Haiyang Zhang wrote: > > > > Changes: > > > > v3: Minor code and comment updates. > > > > v2: Added XDP_TX support. Addressed review comments. > > > > > > How does the locking of the TX path work? You seem to be just > > > calling the normal xmit method, but you don't hold the xmit queue > > > lock, so the stack can start xmit concurrently, no? > > > > The netvsc and vmbus can handle concurrent transmits, except the msd > > (Multi-Send Data) field which can only be used by one queue. > > > > I already added a new flag to netvsc_send(), so packets from XDP_TX > > won't use the msd. >=20 > I see, there's a few non-atomic counters there, but maybe that's not a bi= g deal. Yes, those error counters are used less frequently, and not necessary to be= precise. > What frees the skb if the ring is full, and netvsc_send_pkt() returns -EA= GAIN? > Nothing checks the return value from netvsc_xdp_xmit(). Good catch! I will add skb free when -EAGAIN is returned for XDP_TX. I will update the patch. Thanks, - Haiyang