From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net-next RFC WIP] Patch for XDP support for virtio_net Date: Wed, 26 Oct 2016 20:07:19 +0300 Message-ID: <20161026200153-mutt-send-email-mst@kernel.org> References: <1477109243-29520-1-git-send-email-shrijeet@gmail.com> <20161026155202.5d99d935@redhat.com> <20161026185743-mutt-send-email-mst@kernel.org> <20161026.125245.1630138589657247338.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: brouer@redhat.com, shrijeet@gmail.com, tom@herbertland.com, netdev@vger.kernel.org, shm@cumulusnetworks.com, roopa@cumulusnetworks.com, nikolay@cumulusnetworks.com To: David Miller Return-path: Received: from mx1.redhat.com ([209.132.183.28]:41114 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755000AbcJZRHV (ORCPT ); Wed, 26 Oct 2016 13:07:21 -0400 Content-Disposition: inline In-Reply-To: <20161026.125245.1630138589657247338.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Oct 26, 2016 at 12:52:45PM -0400, David Miller wrote: > From: "Michael S. Tsirkin" > Date: Wed, 26 Oct 2016 19:36:45 +0300 > > > On Wed, Oct 26, 2016 at 03:52:02PM +0200, Jesper Dangaard Brouer wrote: > >> On Sat, 22 Oct 2016 04:07:23 +0000 > >> Shrijeet Mukherjee wrote: > >> > >> > This patch adds support for xdp ndo and also inserts the xdp program > >> > call into the merged RX buffers and big buffers paths > >> > >> I really appreciate you are doing this for virtio_net. > >> > >> My first question is: Is the (packet) page data writable? > >> (MST might be able to answer?) > >> > >> As this is currently an XDP requirement[1]. > > > > I'm not sure I understand what does writable mean. > > Could you explain a bit more pls? > > We do copy data into skb ATM but I plan to change that. > > The packet data area must be writable, This is the part I don't fully understand. It's in RAM so of course it's writeable. > and the page it lives in must > not be shared with any other entity in the system. We share pages between arbitrary multiple packets. I think that's OK - or is there an assumption that multiple programs will be attached with different priveledges? > This is because the eBPF program that executes via XDP must be able > to modify and read arbitrary parts of the packet area. -- MST