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RE: [Xen-devel] allocating AGP aperture memory

To: "Langsdorf, Mark" <mark.langsdorf@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] allocating AGP aperture memory
From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Date: Mon, 24 Oct 2005 13:04:13 +0100
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Thread-topic: [Xen-devel] allocating AGP aperture memory
> You're right, I don't really want to do that, but I got 
> inadvertantly sidetracked into thinking I needed AGP support 
> working.  Fortunately, I don't.
> 
> However, if I don't have AGP support working, I need to 
> program the Northbridge registers with the physical address 
> of the GATT (see init_k8_gatt() in arch/xen/x86_64/kernel/pci-gart.c).
> Just doing a __pa() obviously doesn't return meaningful data, 
> which is to be expected.  How should dom0 go about getting it?

You need to allocate the gatt mapping table using alloc_gatt_pages
(dma_alloc_coherent) rather than get_free_pages.

You then want to use virt_to_gart on the address returned.

Ian

 

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