From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?windows-1252?Q?Roger_Pau_Monn=E9?= <roger.pau@citrix.com>
Subject: Re: How to turn off persistent grant in xen
Date: Tue, 19 May 2015 17:41:41 +0200
Message-ID: <555B59B5.9060407@citrix.com>
References: <656dfa391741d97e139b1edaddb59f68@inp-toulouse.fr>
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To: HANNAS YAYA Issa <issa.hannasyaya@enseeiht.fr>, xen-devel@lists.xen.org
List-Id: xen-devel@lists.xenproject.org

El 19/05/15 a les 16.17, HANNAS YAYA Issa ha escrit:
> Hi
> I want to disable persistent grant in xen. I tried to use xenbus to
> disable it. What I did is modifying this line in
> drivers/block/xenblkback/xenbus.c:
> 
> 791    err = xenbus_printf(xbt, dev->nodename, "feature-persistent",
> "%u", 1);
> 
> 
> and put this
> 
> 791    err = xenbus_printf(xbt, dev->nodename, "feature-persistent",
> "%u", 0);
> 
> but the problem is my domain crash.
> 
> I think it is not the only thing to do in order to disable persistent
> grant.

You only disabled it in the backend, so blkfront is announcing
persistent grant support while blkback is not. This means that blkback
will use persistent grants (because it sees the frontend supports them),
but blkfront will not.

You also need to disable the feature announcement from the frontend,
just grep for feature-persistent in xen-blkfront.c.

Roger.