From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH v2] virtio_net: fix PAGE_SIZE > 64k Date: Tue, 24 Jan 2017 22:45:37 +0200 Message-ID: <20170124221114-mutt-send-email-mst@kernel.org> References: <1485197869-11350-1-git-send-email-mst@redhat.com> <20170124.144227.2017106704873029028.davem@davemloft.net> <20170124215214-mutt-send-email-mst@kernel.org> <20170124.150959.1708982899683381291.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, jasowang@redhat.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, john.fastabend@gmail.com To: David Miller Return-path: Content-Disposition: inline In-Reply-To: <20170124.150959.1708982899683381291.davem@davemloft.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, Jan 24, 2017 at 03:09:59PM -0500, David Miller wrote: > From: "Michael S. Tsirkin" > Date: Tue, 24 Jan 2017 21:53:13 +0200 > > > I didn't realise. Why can't we? I thought that adjust_header is an > > optional feature that userspace can test for, so no rush. > > No, we want the base set of XDP features to be present in all drivers > supporting XDP. I see, I didn't realize this. In light of this, is there any guidance *how much* head room is required to be considered valid? We already have 12 bytes of headroom. I'm generally sorry it's taking long, a large part of that is difficulty figuring out the requirements: when we discussed this on LPC my take-away was that one of the first users will be fighting DDOS attacks. In light of this, I assumed that - supporting just DROP (or DROP+TX) would already be useful - XDP_PASS shouldn't be too slow as some people will run all their traffic with XDP enabled - people actually want this in virtio because they run in a vm Since then I heard opinions that seem to imply that - you must support all features, not just DROP, otherwise it's useless - XDP_PASS is a slow path fallback as people are not expected to mix XDP with regular sockets - DDOS protection and by extension XDP in virtio is a developer's toy anyway Thus, expect some slowness while I figure it all out. -- MST