From mboxrd@z Thu Jan  1 00:00:00 1970
From: joro@8bytes.org (Joerg Roedel)
Date: Mon, 14 Nov 2016 17:20:37 +0100
Subject: [RFC v2 8/8] iommu/arm-smmu: implement add_reserved_regions
 callback
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 <20161111114223.GP2078@8bytes.org>
 <79da09b8-ac1e-cebf-5393-7d67f002b3e3@redhat.com>
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Message-ID: <20161114162037.GC14829@8bytes.org>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Mon, Nov 14, 2016 at 05:08:16PM +0100, Auger Eric wrote:
> There are potentially several MSI doorbell physical pages in the SOC
> that are accessed through the IOMMU (translated). Each of those must
> have a corresponding IOVA and IOVA/PA mapping programmed in the IOMMU.
> Else MSI will fault.
> 
> - step 1 was to define a usable IOVA range for MSI mapping. So now we
> decided the base address and size would be hardcoded for ARM. The
> get_dm_region can be used to retrieve that hardcoded region.
> - Step2 is to allocate IOVAs within that range and map then for each of
> those MSI doorbells. This is done in the MSI controller compose() callback.
> 
> I hope I succeeded in clarifying this time.
> 
> Robin sent today a new version of its cookie think using a dummy
> allocator. I am currently integrating it.

Okay, I understand. A simple bitmap-allocator would probably be
sufficient, and doesn't have the overhead the iova allocator has. About
how many pages are we talking here?


	Joerg