Re: [Xen-devel] [PATCH v1 00/20] Make ACPI builder available to components other than hvmloader

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.07.16 at 11:14, <julien.grall@xxxxxxx> wrote:
> On 07/07/16 09:35, Jan Beulich wrote:
>>>>> On 06.07.16 at 18:32, <boris.ostrovsky@xxxxxxxxxx> wrote:
>>> On 07/06/2016 12:04 PM, Roger Pau Monné wrote:
>>>> On Tue, Jul 05, 2016 at 03:04:59PM -0400, Boris Ostrovsky wrote:
>>>>> * Don't set HW_REDUCED_ACPI flags: this flag is only available starting 
>>>>> with ACPI v5
>>>> Hm, I still think HW_REDUCED_ACPI should be set for the time being,
>>>> considering that we don't provide PM timer or RTC for example. Not setting
>>>> this would be a violation of the ACPI specification, and would mean
>>>> introducing Xen specific hacks yet again to guest OSes, in order to disable
>>>> those devices.
>>>>
>>>> Is the fact that HW_REDUCED_ACPI was introduced in ACPI v5 a problem?
>>>
>>> Yes, because we build v2 tables and they are somewhat different.
>>
>> So couldn't we switch to building v5 tables (or even v6) for PVH
>> (and perhaps re-using the "acpi=" config setting to allow specifying a
>> version - with any value above 1 indicating the requested version)? I
>> certainly agree that setting a v5 flag in a v2 table is bad (best we can
>> hope for is that any consumer would ignore such a flag).
> 
> FWIW, if we switch to ACPI v5.1 or later, it will be easier to merge the 
> ACPI building code with ARM.

I don't think we can outright switch to v5 or newer on x86 - old
guests (say WinXP) may not be able to deal with that.

Jan

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