Konrad Rzeszutek Wilk
2012-Sep-21 20:05 UTC
Re: [PATCH] Xen backend support for paged out grant targets V4.
On Fri, Sep 21, 2012 at 03:30:01PM -0400, Andres Lagar-Cavilla wrote:> On Sep 21, 2012, at 2:52 PM, Konrad Rzeszutek Wilk wrote: > > > On Mon, Sep 17, 2012 at 05:29:24AM -0400, Andres Lagar-Cavilla wrote: > >> On Sep 17, 2012, at 4:17 AM, Ian Campbell wrote: > >> > >>> (I think I forgot to hit send on this on Friday, sorry. Also > >>> s/xen.lists.org/lists.xen.org in the CC line…) > >> I'm on a roll here… > >> > >>> > >>> On Fri, 2012-09-14 at 15:26 +0100, Andres Lagar-Cavilla wrote: > >>>> Since Xen-4.2, hvm domains may have portions of their memory paged out. When a > >>>> foreign domain (such as dom0) attempts to map these frames, the map will > >>>> initially fail. The hypervisor returns a suitable errno, and kicks an > >>>> asynchronous page-in operation carried out by a helper. The foreign domain is > >>>> expected to retry the mapping operation until it eventually succeeds. The > >>>> foreign domain is not put to sleep because itself could be the one running the > >>>> pager assist (typical scenario for dom0). > >>>> > >>>> This patch adds support for this mechanism for backend drivers using grant > >>>> mapping and copying operations. Specifically, this covers the blkback and > >>>> gntdev drivers (which map foregin grants), and the netback driver (which copies > >>> > >>> foreign > >>> > >>>> foreign grants). > >>>> > >>>> * Add a retry method for grants that fail with GNTST_eagain (i.e. because the > >>>> target foregin frame is paged out). > >>> > >>> foreign > >>> > >>>> * Insert hooks with appropriate wrappers in the aforementioned drivers. > >>>> > >>>> The retry loop is only invoked if the grant operation status is GNTST_eagain. > >>>> It guarantees to leave a new status code different from GNTST_eagain. Any other > >>>> status code results in identical code execution as before. > >>>> > >>>> The retry loop performs 256 attempts with increasing time intervals through a > >>>> 32 second period. It uses msleep to yield while waiting for the next retry. > >>> [...] > >>>> Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org> > >>> > >>> Acked-by: Ian Campbell <ian.campbell@citrix.com> > >>> > >>> Since this is more about grant tables than netback this should probably > >>> go via Konrad rather than Dave, is that OK with you Dave? > >> > >> If that is the case hopefully Konrad can deal with the two typos? Otherwise happy to re-spin the patch. > > > > So with this patch when I launch an PVHVM guest on Xen 4.1 I get this > > in the initial domain and the guest is crashed: > > > > [ 261.927218] privcmd_fault: vma=ffff88002a31dce8 7f4edc095000-7f4edc195000, pgoff=c8, uv=00007f4edc15d000 > > With this patch? Or with the mmapbatch v2? This is a page fault in a foreign-mapped VMA. Not touched by this grant backend patch we are talking about.This patch. But I also had a modified blkback. So let me double check that it is not the persistent grants and this patch doing something naughty.> > Does the hypervisor dump anything to its console? > > At which point during xc_hvm_build do you see this? (or elsewhere in the toolstack?)No idea. Didn't examine that much. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel