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Tue, 19 Nov 2019 15:13:42 +0000 (UTC) Received: from carbon (ovpn-200-17.brq.redhat.com [10.40.200.17]) by smtp.corp.redhat.com (Postfix) with ESMTP id AE6AF605BC; Tue, 19 Nov 2019 15:13:33 +0000 (UTC) Date: Tue, 19 Nov 2019 16:13:32 +0100 From: Jesper Dangaard Brouer To: Lorenzo Bianconi , mcroce@redhat.com Cc: Lorenzo Bianconi , netdev@vger.kernel.org, davem@davemloft.net, ilias.apalodimas@linaro.org, jonathan.lemon@gmail.com, brouer@redhat.com Subject: Re: [PATCH v4 net-next 2/3] net: page_pool: add the possibility to sync DMA memory for device Message-ID: <20191119161332.56faa205@carbon> In-Reply-To: <20191119121430.GA3449@localhost.localdomain> References: <84b90677751f54c1c8d47f4036bce5999982379c.1574083275.git.lorenzo@kernel.org> <20191119122358.12276da4@carbon> <20191119121430.GA3449@localhost.localdomain> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-MC-Unique: 7YKBntXTNeuUxsmSU44lFw-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, 19 Nov 2019 14:14:30 +0200 Lorenzo Bianconi wrote: > > On Mon, 18 Nov 2019 15:33:45 +0200 > > Lorenzo Bianconi wrote: > > =20 > > > diff --git a/include/net/page_pool.h b/include/net/page_pool.h > > > index 1121faa99c12..6f684c3a3434 100644 > > > --- a/include/net/page_pool.h > > > +++ b/include/net/page_pool.h > > > @@ -34,8 +34,15 @@ > > > #include > > > #include > > > =20 > > > -#define PP_FLAG_DMA_MAP 1 /* Should page_pool do the DMA map/unmap *= / > > > -#define PP_FLAG_ALL=09PP_FLAG_DMA_MAP > > > +#define PP_FLAG_DMA_MAP=09=091 /* Should page_pool do the DMA map/un= map */ > > > +#define PP_FLAG_DMA_SYNC_DEV=092 /* if set all pages that the driver= gets > > > +=09=09=09=09 * from page_pool will be > > > +=09=09=09=09 * DMA-synced-for-device according to the > > > +=09=09=09=09 * length provided by the device driver. > > > +=09=09=09=09 * Please note DMA-sync-for-CPU is still > > > +=09=09=09=09 * device driver responsibility > > > +=09=09=09=09 */ > > > +#define PP_FLAG_ALL=09=09(PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV) > > > =20 > > [...] > >=20 > > Can you please change this to use the BIT(X) api. > >=20 > > #include > >=20 > > #define PP_FLAG_DMA_MAP=09=09BIT(0) > > #define PP_FLAG_DMA_SYNC_DEV=09BIT(1) =20 >=20 > Hi Jesper, >=20 > sure, will do in v5 >=20 > >=20 > >=20 > > =20 > > > diff --git a/net/core/page_pool.c b/net/core/page_pool.c > > > index dfc2501c35d9..4f9aed7bce5a 100644 > > > --- a/net/core/page_pool.c > > > +++ b/net/core/page_pool.c > > > @@ -47,6 +47,13 @@ static int page_pool_init(struct page_pool *pool, > > > =09 (pool->p.dma_dir !=3D DMA_BIDIRECTIONAL)) > > > =09=09return -EINVAL; > > > =20 > > > +=09/* In order to request DMA-sync-for-device the page needs to > > > +=09 * be mapped > > > +=09 */ > > > +=09if ((pool->p.flags & PP_FLAG_DMA_SYNC_DEV) && > > > +=09 !(pool->p.flags & PP_FLAG_DMA_MAP)) > > > +=09=09return -EINVAL; > > > + =20 > >=20 > > I like that you have moved this check to setup time. > >=20 > > There are two other parameters the DMA_SYNC_DEV depend on: > >=20 > > =09struct page_pool_params pp_params =3D { > > =09=09.order =3D 0, > > -=09=09.flags =3D PP_FLAG_DMA_MAP, > > +=09=09.flags =3D PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV, > > =09=09.pool_size =3D size, > > =09=09.nid =3D cpu_to_node(0), > > =09=09.dev =3D pp->dev->dev.parent, > > =09=09.dma_dir =3D xdp_prog ? DMA_BIDIRECTIONAL : DMA_FROM_DEVICE, > > +=09=09.offset =3D pp->rx_offset_correction, > > +=09=09.max_len =3D MVNETA_MAX_RX_BUF_SIZE, > > =09}; > >=20 > > Can you add a check, that .max_len must not be zero. The reason is > > that I can easily see people misconfiguring this. And the effect is > > that the DMA-sync-for-device is essentially disabled, without user > > realizing this. The not-realizing part is really bad, especially > > because bugs that can occur from this are very rare and hard to catch. = =20 >=20 > I guess we need to check it just if we provide PP_FLAG_DMA_SYNC_DEV. > Something like: >=20 > =09if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV) { > =09=09if (!(pool->p.flags & PP_FLAG_DMA_MAP)) > =09=09=09return -EINVAL; >=20 > =09=09if (!pool->p.max_len) > =09=09=09return -EINVAL; > =09} Yes, exactly. > >=20 > > I'm up for discussing if there should be a similar check for .offset. > > IMHO we should also check .offset is configured, and then be open to > > remove this check once a driver user want to use offset=3D0. Does the > > mvneta driver already have a use-case for this (in non-XDP mode)? =20 >=20 > With 'non-XDP mode' do you mean not loading a BPF program? If so yes, it = used > in __page_pool_alloc_pages_slow getting pages from page allocator. > What would be a right min value for it? Just 0 or > XDP_PACKET_HEADROOM/NET_SKB_PAD? I guess here it matters if a BPF program= is > loaded or not. I think you are saying, that we need to allow .offset=3D=3D0, because it is used by mvneta. Did I understand that correctly? --=20 Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer