Re: [Xen-devel] [PATCH][VTD] enable integrated graphics passthrough for Calpella and Sandybridge

[Jean Guyader <jean.guyader@xxxxxxxxx>]

On 9 June 2010 16:57, Stefano Stabellini
<stefano.stabellini@xxxxxxxxxxxxx> wrote:
> On Tue, 8 Jun 2010, Kay, Allen M wrote:
>> Stephano,
>>
>> Thanks for your feedback.  I add "#ifdef CONFIG_PASSTHROUGH" in the next 
>> version of the patch.
>>
>> I have tested the patch on a Intel Montevina software development platform 
>> and found it has the same behavior as current xen qemu upstream.
>>
>> Can others who have been playing with IGD passthrough give the patch a try 
>> on older platforms?
>>
>
> Are there any older platforms without opregion support?
> If that is the case what is the result of executing this code on such a
> platform?
>
> +    /* 1:1 map ASL Storage register value */
> +    igd_opregion = pt_pci_host_read(0, 2, 0, 0xfc, 4);
> +    PT_LOG("register_vga: igd_opregion = %x\n", igd_opregion);
> +    ret |= xc_domain_memory_mapping(xc_handle, domid,
> +            igd_opregion >> XC_PAGE_SHIFT,
> +            igd_opregion >> XC_PAGE_SHIFT,
> +            2,
> +            DPCI_ADD_MAPPING);
>
>

We are using a fixed and reserved address in the guest to map this
region, 0xfed00000.
You need to add that in the e820 table as ACPI_NVS so the guest won't
try to use it for
something else. You also have to trap the pci_config space read for
0xfc and give 0xfed00000
back to the guest.

We've notice that on some system the value at 0xfc wasn't align on a
page, so make sure
you do that first.

Jean

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