From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?B?Um9nZXIgUGF1IE1vbm7DqQ==?= Subject: Re: Rebooting domu fails in nfs share exported from another domu on the same dom0 Date: Thu, 17 Jul 2014 17:49:28 +0200 Message-ID: <53C7F088.5070005@citrix.com> References: <53C6E24D.7050903@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <53C6E24D.7050903@oracle.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: annie li , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 16/07/14 22:36, annie li wrote: > Hi > > I hit a problem in such scenario: vm1 is running and export nfs service, > dom0 mount this nfs, and vm2 is booted in this nfs location. vm1 and vm2 > are running on the same dom0. > > When this bug happens, the data flow is: vm2 blkfront-> vm2 blkback-> > loop -> nfs file -> nfs client -> bridge priv1 -> vm1 vif -> vm1 netback > -> vm1 netfront. > > In above data flow, nfs implements direct io, blkfront and blkback uses > grantmap. This makes page mapping works well through vm2 blkfront to vm1 > netback. However, when netback does grant copy, the error happens in > this routine: If it's the same error I was seeing (which I think it is), the problem is due to trying to do a grant_copy with the PFN of a grant mapped page in Dom0, which Xen refuses to perform. I've never followed it up, but I think the problem should be fixed in Linux, so that netback realises it is trying to perform a grant_copy to a granted page, and use the grant ref instead of the PFN. Roger.