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Date: Mon, 10 Jan 2011 10:32:51 +0000
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
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To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
CC: Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
        Jeremy Fitzhardinge <Jeremy.Fitzhardinge@citrix.com>,
        Ian Campbell <Ian.Campbell@eu.citrix.com>,
        Jeremy Fitzhardinge <jeremy@goop.org>,
        "Derek G. Murray" <Derek.Murray@cl.cam.ac.uk>,
        Gerd Hoffmann <kraxel@redhat.com>
Subject: Re: [PATCH 06/11] xen: gntdev: move use of GNTMAP_contains_pte next
 to the map_op
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On Wed, 5 Jan 2011, Konrad Rzeszutek Wilk wrote:
> On Wed, Dec 15, 2010 at 01:40:41PM +0000, stefano.stabellini@eu.citrix.com wrote:
> > From: Ian Campbell <ian.campbell@citrix.com>
> > 
> > This flag controls the meaning of gnttab_map_grant_ref.host_addr and
> > specifies that the field contains a refernce to the pte entry to be
>                                       ^^^^^^^^ - reference

fixed it

> > diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> > index cf61c7d..b916d6b 100644
> > --- a/drivers/xen/gntdev.c
> > +++ b/drivers/xen/gntdev.c
> > @@ -205,10 +205,12 @@ static int find_grant_ptes(pte_t *pte, pgtable_t token, unsigned long addr, void
> >  	BUG_ON(pgnr >= map->count);
> >  	pte_maddr  = (u64)pfn_to_mfn(page_to_pfn(token)) << PAGE_SHIFT;
> >  	pte_maddr += (unsigned long)pte & ~PAGE_MASK;
> > -	gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr, map->flags,
> > +	gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr,
> > +			  GNTMAP_contains_pte | map->flags,
> 
> Ok, but the gnttab_set_map_op will do the exact thing it did before. It still does this:
> 
> map->host_addr = addr;
> 
> irregardless if you pass in any flag.
> 

Yes, but the flags are set in map_ops and that is critical because it
changes the meanings of the hypercall arguments.