Re: [Qemu-devel] [V3 3/4] hw/i386: ACPI table for AMD IO MMU

[Jan Kiszka <jan.kiszka@web.de>]

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On 2016-01-14 17:09, David kiarie wrote:
> On Thu, Jan 14, 2016 at 6:42 PM, Jan Kiszka <jan.kiszka@web.de> wrote:
>> On 2016-01-14 16:39, Michael S. Tsirkin wrote:
>>> On Thu, Jan 14, 2016 at 03:15:38PM +0300, David kiarie wrote:
>>>> On Thu, Jan 14, 2016 at 1:09 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
>>>>> On Thu, Jan 14, 2016 at 11:04:27AM +0300, David Kiarie wrote:
>>>>>> Add IVRS table for AMD IO MMU. Also reverve MMIO
>>>>>
>>>>> reserve?
>>>>
>>>> Yeah, typo.
>>>>
>>>>>
>>>>>> region for IO MMU via ACPI
>>>>>
>>>>>
>>>>> It does not look like you reserve anything.
>>>>>
>>>>> Pls add a link to hardware spec (in
>>>>> the device implementation) so we can check
>>>>> what does real hardware do.
>>>>>
>>>>> If this is it:
>>>>> http://developer.amd.com/wordpress/media/2012/10/488821.pdf
>>>>>
>>>>> then the way that works seems to be by guest
>>>>> programming the MMIO base.
>>>>> We should do the same: patch seabios and EFI to do this.
>>>>
>>>> Yes, that's the spec.
>>>>
>>>> We thought this could be possible via ACPI (without patching BIOS ), no ?
>>>
>>> I don't see how. We should do it the way it happens on real hardware.
>>>
>>
>> Doesn't Seabios retrieve certain ACPI fragments from QEMU via a
>> pv-interface by now?
>>
>> Anyway, the question remains where this address comes from: The BIOS,
>> which then writes it into some hw config register and reports it in
>> addition via ACPI or the hardware (hard-wired).
> 
> Will look at patching BIOS.

Scanning through the spec again: As the address is not hard-wired but
configured via registers in the extended capabilities of the
corresponding PCI functions of an IOMMU (and also enabled that way!),
it's up to the BIOS to allocate an appropriate address for a system.

Jan



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