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

[Al Stone <al.stone@xxxxxxxxxx>]

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.

-- 
ciao,
al
-----------------------------------
Al Stone
Software Engineer
Linaro Enterprise Group
al.stone@xxxxxxxxxx
-----------------------------------

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