Re: [Xen-devel] [PATCH 00/14] Xen ARM DomU ACPI support

[Shannon Zhao <shannon.zhao@xxxxxxxxxx>]

On 2016年06月01日 21:21, Julien Grall wrote:
> 
> 
> On 01/06/16 13:59, Boris Ostrovsky wrote:
>> On 06/01/2016 08:42 AM, Julien Grall wrote:
>>> On 31/05/16 21:51, Boris Ostrovsky wrote:
>>>> On 05/31/2016 03:42 PM, Konrad Rzeszutek Wilk wrote:
>>>>> On Tue, May 31, 2016 at 12:43:22PM +0800, Shannon Zhao wrote:
>>>>>> From: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
>>>>>>
>>>>>> The design of this feature is described as below.
>>>>>> Firstly, the toolstack (libxl) generates the ACPI tables according
>>>>>> the
>>>>>> number of vcpus and gic controller.
>>>>> CC-ing Boris - who has been working on exposing ACPI tables
>>>>> for PVH guests.
>>>>>
>>>>> Is there some way of re-using some of the code?
>>>>
>>>> Indeed it would be good to keep all ACPI code in single place.
>>>>
>>>> I sent a patch series a while ago
>>>> (http://lists.xenproject.org/archives/html/xen-devel/2016-04/msg00625.html)
>>>>
>>>>
>>>> but because of release work it hasn't been reviewed yet. Shannon, can
>>>> you take a look at it and see whether you code can make use of what is
>>>> proposed there? It builds all the tables that you are building here
>>>> except for GTDT and provides libxc interface.
>>>
>>> AFAICT, your library is creating ACPI 1.0/2.0 tables. However the
>>> support for ARM has been added in ACPI 5.1.
>>>
>>> Looking at the list of tables built by the library, we might be able
>>> to re-use the code for SRAT, SLIT, FADT, RSDP. The rest is x86
>>> specific (WAET, MADT, HPET, SSDT_{PM,S3,S4}, TCPA (?)).
>>
>> The interface allows choosing which tables to generate so that shouldn't
>> be a problem.
> 
> Would it be possible to opt-out some of the tables at built-time. Maybe
> by moving the code in separate files?
> 
>>>
>>> In the current state, I think the benefits for ARM is very limited. I
>>> agree that having a common library to manipulate ACPI would be nice,
>>> however, this would need a better abstraction to support different
>>> version and avoid to build unnecessary code.
>>>
>>
>> Can you suggest improvements to that series so that (even if not now but
>> at some point later) it is easier to integrate ARM and x86? Again, this
>> code is an RFC so now is the time to do it right.
> 
> I agree :). I think the 2 points that would make easier to integrate ARM
> are:
>    - Newer version of ACPI (I know that you need to keep ACPI 1.0/2.0
> for some old guests).
>    - Possibility to have per-arch tables and fields. For instance the
> MADT will be different for ARM. Also, some fields in the FADT are ARM
> specific (see arm_boot_flags).
> 
> I have not yet review this series, so it is my best guess. Shannon, any
> opinions?
Actually I think there are two tables can be reused: RSDP and XSDT(while
which are smaller codes, I don't think it needs to be mixed with
others). The other tables are arch specific because the contents are
totally different. So if we want to add some generic generating table
funtions, we might pass a lot of arch specific information to these
functions which looks like inconvenient and ugly.
And this situation for x86 and ARM is similar with QEMU. You can have a
look at hw/arm/virt-acpi-build.c and hw/i386/acpi-build.c in QEMU source
code. The two only reuse the build_rsdt() function.

Thanks,
-- 
Shannon

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