From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net] vhost_net: remove VHOST_NET_F_VIRTIO_NET_HDR support Date: Mon, 11 Jun 2018 06:08:34 +0300 Message-ID: <20180611060759-mutt-send-email-mst@kernel.org> References: <1528429842-22835-1-git-send-email-jasowang@redhat.com> <20180608074115-mutt-send-email-mst@kernel.org> <23efe110-f61a-5aee-c0b4-bd3dc5426438@redhat.com> <20180611050741-mutt-send-email-mst@kernel.org> <90e9b3ea-e9d2-d60d-8355-42d447c67452@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Disposition: inline In-Reply-To: <90e9b3ea-e9d2-d60d-8355-42d447c67452@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Jason Wang Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org List-Id: 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certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B5C8879D36; Mon, 11 Jun 2018 03:08:34 +0000 (UTC) Received: from redhat.com (ovpn-120-77.rdu2.redhat.com [10.10.120.77]) by smtp.corp.redhat.com (Postfix) with ESMTP id 60C5B63F32; Mon, 11 Jun 2018 03:08:34 +0000 (UTC) Date: Mon, 11 Jun 2018 06:08:34 +0300 From: "Michael S. Tsirkin" To: Jason Wang Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net] vhost_net: remove VHOST_NET_F_VIRTIO_NET_HDR support Message-ID: <20180611060759-mutt-send-email-mst@kernel.org> References: <1528429842-22835-1-git-send-email-jasowang@redhat.com> <20180608074115-mutt-send-email-mst@kernel.org> <23efe110-f61a-5aee-c0b4-bd3dc5426438@redhat.com> <20180611050741-mutt-send-email-mst@kernel.org> <90e9b3ea-e9d2-d60d-8355-42d447c67452@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <90e9b3ea-e9d2-d60d-8355-42d447c67452@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Mon, 11 Jun 2018 03:08:34 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Mon, 11 Jun 2018 03:08:34 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'mst@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 11, 2018 at 10:29:36AM +0800, Jason Wang wrote: > > > On 2018年06月11日 10:12, Michael S. Tsirkin wrote: > > On Fri, Jun 08, 2018 at 01:07:09PM +0800, Jason Wang wrote: > > > > > > On 2018年06月08日 12:46, Michael S. Tsirkin wrote: > > > > On Fri, Jun 08, 2018 at 11:50:42AM +0800, Jason Wang wrote: > > > > > This feature bit is duplicated with VIRTIO_F_ANY_LAYOUT, this means if > > > > > a userpsace want to enable VRITIO_F_ANY_LAYOUT, > > > > > VHOST_NET_F_VIRTIO_NET_HDR will be implied too. This is wrong and will > > > > > break networking. > > > > What breaks networking exactly? VHOST_NET supported ANY_LAYOUT > > > > from day one. For this reason it does not need to know about > > > > VRITIO_F_ANY_LAYOUT and we reused the bit for other purposes. > > > It's the knowledge of vhost_net code it self but not userspace. For > > > userspace, it should depends on the value of returned by VHOST_GET_FEATURES. > > > So when userspace can set_features with ANY_LAYOUT, vhost may think it wants > > > VHOST_NET_F_VIRTIO_NET_HDR. > > Yes but that's the admittedly ugly API that we have now. > > userspace is supposed to know VRITIO_F_ANY_LAYOUT does > > not make sense for vhost. > > Ok. > > > > > > > > > > > > > > > > > > > > Fixing this by safely removing > > > > > VHOST_NET_F_VIRTIO_NET_HDR support. There should be very few or even > > > > > no userspace can use this. > > > > Quite possibly, but it is hard to be sure. It seems safer to > > > > maintain it unless there's an actual reason something's broken. > > > I think not since the feature is negotiated not mandatory? > > That doesn't mean much. > > > > > > > Further cleanups could be done for > > > > > -net-next for safety. > > > > > > > > > > In the future, we need a vhost dedicated feature set/get ioctl() > > > > > instead of reusing virtio ones. > > > > Not just in the future, we might want to switch iommu > > > > to a sane structure without the 64 bit padding bug > > > > right now. > > > Yes, I hit this bug when introducing V2 of msg IOTLB message. > > Sounds good, so if you like, reserve a bit for > > VHOST_NET_F_VIRTIO_NET_HDR in the new ioctl mask and > > do not enable it there. > > Ok, and maybe VHOST_F_LOG_ALL. > > > > > > > > Fixes: 4e9fa50c6ccbe ("vhost: move features to core") > > > > This tag makes no sense here IMHO. Looks like people are using some tool > > > > that just looks at the earliest version where patch won't apply. The > > > > commit in question just moved some code around. > > > Looks not, before this commit, vhost_net won't return ANY_LAYOUT. > > > > > > Thanks > > Well ANY_LAYOUT just happens to be same as VHOST_NET_F_VIRTIO_NET_HDR > > and that has been set since forever. > > So do you still want this patch? If not we need to document that ANY_LAYOUT > could not be passed through SET_FEATURES somewhere. > > Thanks Let's document this, yes. I don't think we should drop VHOST_NET_F_VIRTIO_NET_HDR now. > > > > > > > Signed-off-by: Jason Wang > > > > > --- > > > > > drivers/vhost/net.c | 15 +++++---------- > > > > > 1 file changed, 5 insertions(+), 10 deletions(-) > > > > > > > > > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > > > > > index 986058a..83eef52 100644 > > > > > --- a/drivers/vhost/net.c > > > > > +++ b/drivers/vhost/net.c > > > > > @@ -69,7 +69,6 @@ MODULE_PARM_DESC(experimental_zcopytx, "Enable Zero Copy TX;" > > > > > enum { > > > > > VHOST_NET_FEATURES = VHOST_FEATURES | > > > > > - (1ULL << VHOST_NET_F_VIRTIO_NET_HDR) | > > > > > (1ULL << VIRTIO_NET_F_MRG_RXBUF) | > > > > > (1ULL << VIRTIO_F_IOMMU_PLATFORM) > > > > > }; > > > > > @@ -1255,15 +1254,11 @@ static int vhost_net_set_features(struct vhost_net *n, u64 features) > > > > > (1ULL << VIRTIO_F_VERSION_1))) ? > > > > > sizeof(struct virtio_net_hdr_mrg_rxbuf) : > > > > > sizeof(struct virtio_net_hdr); > > > > > - if (features & (1 << VHOST_NET_F_VIRTIO_NET_HDR)) { > > > > > - /* vhost provides vnet_hdr */ > > > > > - vhost_hlen = hdr_len; > > > > > - sock_hlen = 0; > > > > > - } else { > > > > > - /* socket provides vnet_hdr */ > > > > > - vhost_hlen = 0; > > > > > - sock_hlen = hdr_len; > > > > > - } > > > > > + > > > > > + /* socket provides vnet_hdr */ > > > > > + vhost_hlen = 0; > > > > > + sock_hlen = hdr_len; > > > > > + > > > > > mutex_lock(&n->dev.mutex); > > > > > if ((features & (1 << VHOST_F_LOG_ALL)) && > > > > > !vhost_log_access_ok(&n->dev)) > > > > > -- > > > > > 2.7.4