From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Campbell <Ian.Campbell@citrix.com>
Subject: Re: [question]: __gnttab_map_grant_ref()  and  iommu
Date: Wed, 4 Apr 2012 08:28:59 +0100
Message-ID: <1333524539.12209.20.camel@dagon.hellion.org.uk>
References: <20120403191455.6967e409@mantra.us.oracle.com>
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To: Mukesh Rathor <mukesh.rathor@oracle.com>
Cc: "Xen-devel@lists.xensource.com" <Xen-devel@lists.xensource.com>, Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>
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On Wed, 2012-04-04 at 03:14 +0100, Mukesh Rathor wrote:
> I'm not able to figure why __gnttab_map_grant_ref() does PV iommu
> mappings for GNTMAP_host_map. Should it not check for GNTMAP_device_map
> and do for those only?

I don't know but perhaps it is because when the backend maps a foreign
page there is a reasonably high chance that it is eventually going to
end up passing that page to a hardware device (e.g. a physical NIC or
disk controller) for DMA and therefore the mapping must be reflected in
the IOMMU.

Ian.