Re: [Xen-devel] How to find device name in order to fill STAO ACPI table

[G Gregory <graeme.gregory@xxxxxxxxxx>]

On 3 January 2017 at 17:50, Al Stone <al.stone@xxxxxxxxxx> wrote:
> On 12/23/2016 05:51 AM, Roger Pau Monné wrote:
>> Hello,
>>
>> I've been looking into the STAO specification[0], because I think it would 
>> also
>> be useful for x86 PVHv2 Dom0, but I'm not really sure how is Xen supposed to
>> use it.
>>
>> Xen doesn't have an AML parser, so I'm not sure how is it supposed to guess
>> the name of the devices it wants to hide from Dom0. Is there something I'm
>> missing that can be used in order to find out the device name in the ACPI
>> namespace without parsing AML tables?
>>
>> Thanks, Roger.
>>
>> [0] https://lists.xen.org/archives/html/xen-devel/2016-08/pdfYfOWKJ83jH.pdf
>>
>
> I don't know if you've gotten a response to this or not yet....
>
> If you have an ACPI namespace available, then there had to be an AML parser
> and/or interpreter available.  Once devices are enumerated in Linux, for
> example, you can use the device info to get an ACPI handle which can then be
> used to call the interpreter and have it return the ACPI path name.
>
> If you don't have an ACPI namespace available,  you would have to look at
> tools such as libacpi, or reuse parts of QEMU, or the upstream ACPICA
> interpreter to be able to sort through the DSDT/SSDT tables containing the AML
> that would contain the device names.  OpenBSD has such an interpreter, too.
> You don't necessarily have to use the ACPI info, but you do need to be able
> to read the contents of the DSDT/SSDTs to determine device names.
>
> Stefano thought this through in more detail than I did when we were proposing
> the STAO so he probably has additional insights.
>
Back when we originally discussed this I asked the question and the
Xen guys told me that Xen would keep a table per motherboard as there
wasn't a generic discoverable way to find the devices that need
hidden.

Graeme

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