[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH RFC 19/20] acpi: Set HW_REDUCED_ACPI in FADT if IOAPIC is not supported



On 06/07/2016 02:06 AM, Jan Beulich wrote:
>>>> On 06.06.16 at 19:31, <boris.ostrovsky@xxxxxxxxxx> wrote:
>> On 06/06/2016 09:38 AM, Jan Beulich wrote:
>>>>>> On 06.04.16 at 03:25, <boris.ostrovsky@xxxxxxxxxx> wrote:
>>>> With this flags set guests will not try to set up SCI.
>>> I've just read through the respective ACPI spec section again, and
>>> I couldn't find a reference to SCI from there ("Hardware-Reduced
>>> ACPI"). Can you clarify this connection please. Also there are other
>>> consequences of setting that flag, so in order to understand the
>>> reasons behind this change in case of future problems I think the
>>> description here will need to be significantly extended, despite the
>>> change being so small.
>> My understanding is that hardware-reduced platforms don't use ACPI
>> Platform Event Model (Sec. 4.1.1) and that model requires SCI (and vice
>> versa --- SCI is present when ACPI Platform Event Model is in use). The
>> (somewhat indirect) evidence of this is in section 4.6 "The ACPI
>> Hardware Model" where is says: "In the ACPI Legacy state, the ACPI event
>> model is disabled (no SCIs are generated) ..."
> In the sum of all the non-explicit wording I can only convince myself
> that SCI is a prereq for the event model. Yet I could see this being
> an if-and-only-if, just that I couldn't find any place saying so.
>

Not sure how I should interpret this: do you (reluctantly, possibly)
agree that we can use HW-reduced flag to indicate that SCI is not there?

-boris

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel

 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.