From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: Sub page Grant Table mappings Date: Wed, 23 Dec 2015 10:06:14 +0000 Message-ID: <567A7216.3060902@citrix.com> References: <20151222205910.GA24365@kemushi.esdenera.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20151222205910.GA24365@kemushi.esdenera.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Mike Belopuhov , xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 22/12/15 20:59, Mike Belopuhov wrote: > Hi, > > I'm trying to get grant table sub page mappings working on Xen 4.5. > I know there have been some changes in the trunk regarding moving src/ > dst checks closer together, but I can't test this easily atm. Please > bear with me for a moment. Or tell me that it might have been broken > previously. > > What I'm trying to do is to map in a 2k cluster from the networking > stack (we call it an mbuf cluster, you might call it skb something) > onto the Netfront Rx ring. 2 clusters fit one page. Therefore for > one frame address which is a (PA >> 12) I might have 2 entries one > after the other, both with sub_page.length = 2048 but one with a > sub_page.page_off = 2048 and the other with a 0 offset. Both come > with (GTF_permit_access | GTF_sub_page) flags. The netif protocol doesn't allow subpages for Rx requests -- the backend requires a full page to be granted. Note how struct netif_rx_req only has id and gref fields. David