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[146.241.225.251]) by smtp.gmail.com with ESMTPSA id o2-20020a0ce402000000b0063d14bfa5absm4658714qvl.36.2023.08.01.07.04.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Aug 2023 07:04:59 -0700 (PDT) Message-ID: <00f2b7bdb18e0eaa42f0cca542a9530564615475.camel@redhat.com> Subject: Re: [PATCH net-next v5 4/4] vsock/virtio: MSG_ZEROCOPY flag support From: Paolo Abeni To: Arseniy Krasnov , Stefan Hajnoczi , Stefano Garzarella , "David S. Miller" , Eric Dumazet , Jakub Kicinski , "Michael S. Tsirkin" , Jason Wang , Bobby Eshleman Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@sberdevices.ru, oxffffaa@gmail.com Date: Tue, 01 Aug 2023 16:04:55 +0200 In-Reply-To: <1c9f9851-2228-c92b-ce3d-6a84d44e6628@sberdevices.ru> References: <20230730085905.3420811-1-AVKrasnov@sberdevices.ru> <20230730085905.3420811-5-AVKrasnov@sberdevices.ru> <8a7772a50a16fbbcb82fc0c5e09f9e31f3427e3d.camel@redhat.com> <1c9f9851-2228-c92b-ce3d-6a84d44e6628@sberdevices.ru> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.46.4 (3.46.4-1.fc37) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2023-08-01 at 16:36 +0300, Arseniy Krasnov wrote: >=20 > On 01.08.2023 16:34, Paolo Abeni wrote: > > On Sun, 2023-07-30 at 11:59 +0300, Arseniy Krasnov wrote: > > > +static int virtio_transport_fill_skb(struct sk_buff *skb, > > > + struct virtio_vsock_pkt_info *info, > > > + size_t len, > > > + bool zcopy) > > > +{ > > > + if (zcopy) { > > > + return __zerocopy_sg_from_iter(info->msg, NULL, skb, > > > + &info->msg->msg_iter, > > > + len); > > > + } else { > >=20 > >=20 > > No need for an else statement after 'return' > >=20 > > > + void *payload; > > > + int err; > > > + > > > + payload =3D skb_put(skb, len); > > > + err =3D memcpy_from_msg(payload, info->msg, len); > > > + if (err) > > > + return -1; > > > + > > > + if (msg_data_left(info->msg)) > > > + return 0; > > > + > >=20 > > This path does not update truesize, evem if it increases the skb len... >=20 > Thanks, I'll fix it. >=20 > >=20 > > > + return 0; > > > + } > > > +} > >=20 > > [...] > >=20 > > > @@ -214,6 +251,70 @@ static u16 virtio_transport_get_type(struct sock= *sk) > > > return VIRTIO_VSOCK_TYPE_SEQPACKET; > > > } > > > =20 > > > +static struct sk_buff *virtio_transport_alloc_skb(struct vsock_sock = *vsk, > > > + struct virtio_vsock_pkt_info *info, > > > + size_t payload_len, > > > + bool zcopy, > > > + u32 src_cid, > > > + u32 src_port, > > > + u32 dst_cid, > > > + u32 dst_port) > > > +{ > > > + struct sk_buff *skb; > > > + size_t skb_len; > > > + > > > + skb_len =3D VIRTIO_VSOCK_SKB_HEADROOM; > > > + > > > + if (!zcopy) > > > + skb_len +=3D payload_len; > > > + > > > + skb =3D virtio_vsock_alloc_skb(skb_len, GFP_KERNEL); > > > + if (!skb) > > > + return NULL; > > > + > > > + virtio_transport_init_hdr(skb, info, src_cid, src_port, > > > + dst_cid, dst_port, > > > + payload_len); > > > + > > > + /* Set owner here, because '__zerocopy_sg_from_iter()' uses > > > + * owner of skb without check to update 'sk_wmem_alloc'. > > > + */ > > > + if (vsk) > > > + skb_set_owner_w(skb, sk_vsock(vsk)); > >=20 > > ... which can lead to bad things(TM) if the skb goes trough some later > > non trivial processing, due to the above skb_set_owner_w(). > >=20 > > Additionally can be the following condition be true: > >=20 > > vsk =3D=3D NULL && (info->msg && payload_len > 0) && zcopy > >=20 > > ??? >=20 > No, vsk =3D=3D NULL only when we reset connection, in that case both info= ->msg =3D=3D NULL and payload_len =3D=3D 0, > as this is control message without any data. Perhaps a comment with possibly even a WARN_ON_ONCE(!) could help ;) Thanks! Paolo