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Re: [Xen-devel] grant table interface addition?

To: Jan Beulich <jbeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] grant table interface addition?
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Thu, 30 Oct 2008 15:58:01 +0000
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On 30/10/08 15:53, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

>>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 30.10.08 15:15 >>>
>> On 30/10/08 14:06, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:
>>> As to PAGE_IO, wouldn't it be appropriate to set this flag on pte-s created
>>> with GNTMAP_device_map? Or is the name misleading me? I'm perhaps
>>> confused by the fact that the use of this flag is not tied to granting iomem
>>> pages...
>> 
>> The idea was that this would grant-map pages into an iommu. Really it's not
>> actually been used, but GNTMAP_device_map doesn't cause mappings to appear
>> in host page tables.
> 
> It actually is being used in Solarflare's acceleration backend - what you say
> makes me think this could be wrong then.

I suppose it's useful if you only want the machine address of the granted
page, and don't care about getting a host mapping.

 -- Keir



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