From mboxrd@z Thu Jan 1 00:00:00 1970 From: annie li Subject: Re: Rebooting domu fails in nfs share exported from another domu on the same dom0 Date: Thu, 17 Jul 2014 12:56:12 -0400 Message-ID: <53C8002C.2020501@oracle.com> References: <53C6E24D.7050903@oracle.com> <53C7F088.5070005@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <53C7F088.5070005@citrix.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: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= Cc: "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 2014/7/17 11:49, Roger Pau Monn=E9 wrote: > 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. > I guess the routine is similar if using grant ref. See __gnttab_copy = function, The routine goes into __acquire_grant_for_copy for grant ref, and then = __get_paged_frame->get_page_from_gfn->get_page. get_page is where the = checking page owner fails. Thanks Annie