Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934282AbcJUNYb (ORCPT ); Fri, 21 Oct 2016 09:24:31 -0400 Received: from mail-qk0-f196.google.com ([209.85.220.196]:33426 "EHLO mail-qk0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933582AbcJUNY3 (ORCPT ); Fri, 21 Oct 2016 09:24:29 -0400 From: Aaron Conole To: "Michael S. Tsirkin" Cc: Jarod Wilson , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, "K. Y. Srinivasan" , Haiyang Zhang , Shrikrishna Khare , "VMware\, Inc." , Wei Liu , Paul Durrant , David Kershner Subject: Re: [PATCH net-next v2 6/9] net: use core MTU range checking in virt drivers References: <20161019023333.15760-1-jarod@redhat.com> <20161020175524.6184-1-jarod@redhat.com> <20161020175524.6184-7-jarod@redhat.com> <20161020231559-mutt-send-email-mst@kernel.org> <20161021023720.GA11396@redhat.com> <20161021063505-mutt-send-email-mst@kernel.org> Date: Fri, 21 Oct 2016 09:24:25 -0400 In-Reply-To: <20161021063505-mutt-send-email-mst@kernel.org> (Michael S. Tsirkin's message of "Fri, 21 Oct 2016 06:36:25 +0300") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3593 Lines: 92 "Michael S. Tsirkin" writes: > On Thu, Oct 20, 2016 at 10:37:20PM -0400, Jarod Wilson wrote: >> On Thu, Oct 20, 2016 at 11:23:54PM +0300, Michael S. Tsirkin wrote: >> > On Thu, Oct 20, 2016 at 01:55:21PM -0400, Jarod Wilson wrote: >> ... >> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c >> > > index fad84f3..720809f 100644 >> > > --- a/drivers/net/virtio_net.c >> > > +++ b/drivers/net/virtio_net.c >> > > @@ -1419,17 +1419,6 @@ static const struct ethtool_ops virtnet_ethtool_ops = { >> > > .set_settings = virtnet_set_settings, >> > > }; >> > > >> > > -#define MIN_MTU 68 >> > > -#define MAX_MTU 65535 >> > > - >> > > -static int virtnet_change_mtu(struct net_device *dev, int new_mtu) >> > > -{ >> > > - if (new_mtu < MIN_MTU || new_mtu > MAX_MTU) >> > > - return -EINVAL; >> > > - dev->mtu = new_mtu; >> > > - return 0; >> > > -} >> > > - >> > > static const struct net_device_ops virtnet_netdev = { >> > > .ndo_open = virtnet_open, >> > > .ndo_stop = virtnet_close, >> > > @@ -1437,7 +1426,6 @@ static const struct net_device_ops virtnet_netdev = { >> > > .ndo_validate_addr = eth_validate_addr, >> > > .ndo_set_mac_address = virtnet_set_mac_address, >> > > .ndo_set_rx_mode = virtnet_set_rx_mode, >> > > - .ndo_change_mtu = virtnet_change_mtu, >> > > .ndo_get_stats64 = virtnet_stats, >> > > .ndo_vlan_rx_add_vid = virtnet_vlan_rx_add_vid, >> > > .ndo_vlan_rx_kill_vid = virtnet_vlan_rx_kill_vid, >> > > @@ -1748,6 +1736,9 @@ static bool virtnet_validate_features(struct virtio_device *vdev) >> > > return true; >> > > } >> > > >> > > +#define MIN_MTU ETH_MIN_MTU >> > > +#define MAX_MTU ETH_MAX_MTU >> > > + >> > >> > Can we drop these btw? >> >> Bah. Yeah. Should have just used them directly. I didn't add ETH_MAX_MTU >> until after doing the virtio_net changes, so I missed that. >> >> > > static int virtnet_probe(struct virtio_device *vdev) >> > > { >> > > int i, err; >> > > @@ -1821,6 +1812,10 @@ static int virtnet_probe(struct virtio_device *vdev) >> > > >> > > dev->vlan_features = dev->features; >> > > >> > > + /* MTU range: 68 - 65535 */ >> > > + dev->min_mtu = MIN_MTU; >> > > + dev->max_mtu = MAX_MTU; >> > > + >> > > /* Configuration may specify what MAC to use. Otherwise random. */ >> > > if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC)) >> > > virtio_cread_bytes(vdev, >> > > @@ -1875,8 +1870,10 @@ static int virtnet_probe(struct virtio_device *vdev) >> > > mtu = virtio_cread16(vdev, >> > > offsetof(struct virtio_net_config, >> > > mtu)); >> > > - if (virtnet_change_mtu(dev, mtu)) >> > > + if (mtu < dev->min_mtu || mtu > dev->max_mtu) >> > >> > In fact the > max_mtu branch does not make sense since a 16 bit >> > value can't exceed MAX_MTU. >> >> Hm. mtu is declared as an int, not sure if there's any sort of type >> promotion to be worried about (not an area I know much/anything about). > > Not by design, that's for sure. If you're really worried, we could declare it as a u16. The value returned from virtio_cread16 is type u16, and there are no type promotion rules I'm aware of that would do the wrong thing there. >> Certainly something that could be looked into as a minor optimization, >> though it's only in a probe path and shouldn't hurt anything, so ... meh? > > Right. Aaron said he's working on a patch that essentially does > dev->max_mtu = mtu after validation, so this part will look > a bit silly there. Agreed, but I can do that in my patch if you don't want the extra churn. -Aaron