From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: Keir Fraser <keir@xen.org>, Tim Deegan <tim@xen.org>,
xen-devel@lists.xen.org, Ian Jackson <ian.jackson@eu.citrix.com>,
roger.pau@citrix.com
Subject: Re: [PATCH RFC 19/20] acpi: Set HW_REDUCED_ACPI in FADT if IOAPIC is not supported
Date: Wed, 8 Jun 2016 18:04:01 -0400 [thread overview]
Message-ID: <57589651.5020506@oracle.com> (raw)
In-Reply-To: <5757073302000078000F2B6A@prv-mh.provo.novell.com>
On 06/07/2016 11:41 AM, Jan Beulich wrote:
>>>> On 07.06.16 at 17:17, <boris.ostrovsky@oracle.com> wrote:
>> On 06/07/2016 10:12 AM, Jan Beulich wrote:
>>>>>> On 07.06.16 at 16:02, <boris.ostrovsky@oracle.com> wrote:
>>>> On 06/07/2016 02:06 AM, Jan Beulich wrote:
>>>>>>>> On 06.06.16 at 19:31, <boris.ostrovsky@oracle.com> wrote:
>>>>>> On 06/06/2016 09:38 AM, Jan Beulich wrote:
>>>>>>>>>> On 06.04.16 at 03:25, <boris.ostrovsky@oracle.com> 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?
>>> I really think we need to get confirmation on this from ACPI folks.
>> Who should those people be? linux-acpi?
> That may yield valuable, but not dependable input. I'd rather think of
> folks actually working on / contributing to the spec. I'm sure Intel can
> name a few of their employees ...
>
>>> And I think (and I said so before) we need to understand all the
>>> other implications from setting that flag (i.e. we _cannot_ use this
>>> flag _just_ to indicate there's no SCI).
>> FWIW, the Microsoft's reading is
>> https://msdn.microsoft.com/en-us/windows/hardware/drivers/bringup/hardware-req
>> uirements-for-soc-based-platforms
>>
>> ACPI fixed hardware features such as the following are not required:
>> Power Management (PM) timer
>> Real Time Clock (RTC) wake alarm
>> System Control Interrupt (SCI)
>> Fixed Hardware register set (PMx_* event/control/status registers)
>> GPE block registers (GPEx_* event/control/status registers)
>> Embedded controller
>>
>> Also, from ACPICA perpective, HW-reduced mode appears to be the only way
>> to prevent initialization of SCI.
> Well, we could of course start out with HW-reduced mode, but we'd
> then need to settle on all aspects before any of this becomes fully
> supported.
So it looks like we can avoid needing this mode in Linux by simply
allocating an irq descriptor for the SCI. We shouldn't receive anything
on that interrupt in PVH anyway.
I don't know whether this will work for other OSs (i.e. FreeBSD).
-boris
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next prev parent reply other threads:[~2016-06-08 22:04 UTC|newest]
Thread overview: 91+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-06 1:25 [PATCH RFC 00/20] Make ACPI builder available to components other than hvmloader Boris Ostrovsky
2016-04-06 1:25 ` [PATCH RFC 01/20] hvmloader: Provide hvmloader_acpi_build_tables() Boris Ostrovsky
2016-06-02 12:42 ` Jan Beulich
2016-06-02 16:39 ` Boris Ostrovsky
2016-04-06 1:25 ` [PATCH RFC 02/20] acpi/hvmloader: Move acpi_info initialization out of ACPI code Boris Ostrovsky
2016-06-02 12:54 ` Jan Beulich
2016-06-02 16:54 ` Boris Ostrovsky
2016-06-03 12:13 ` Jan Beulich
2016-06-03 14:42 ` Boris Ostrovsky
2016-06-03 14:55 ` Jan Beulich
2016-06-03 15:29 ` Boris Ostrovsky
2016-04-06 1:25 ` [PATCH RFC 03/20] acpi/hvmloader: Initialize vm_gid data outside " Boris Ostrovsky
2016-06-02 13:03 ` Jan Beulich
2016-06-02 17:01 ` Boris Ostrovsky
2016-04-06 1:25 ` [PATCH RFC 04/20] acpi/hvmloader: Decide which SSDTs to build in hvmloader Boris Ostrovsky
2016-06-02 13:07 ` Jan Beulich
2016-04-06 1:25 ` [PATCH RFC 05/20] acpi/hvmloader: Move passthrough initialization from ACPI code Boris Ostrovsky
2016-06-02 13:52 ` Jan Beulich
2016-04-06 1:25 ` [PATCH RFC 06/20] acpi/hvmloader: Collect processor and NUMA info in hvmloader Boris Ostrovsky
2016-06-02 14:05 ` Jan Beulich
2016-06-02 17:18 ` Boris Ostrovsky
2016-06-03 12:16 ` Jan Beulich
2016-06-03 14:49 ` Boris Ostrovsky
2016-04-06 1:25 ` [PATCH RFC 07/20] acpi/hvmloader: Set TIS header address " Boris Ostrovsky
2016-06-02 14:09 ` Jan Beulich
2016-04-06 1:25 ` [PATCH RFC 08/20] acpi/hvmloader: Make providing IOAPIC in MADT optional Boris Ostrovsky
2016-04-06 1:25 ` [PATCH RFC 09/20] acpi/hvmloader: Build WAET optionally Boris Ostrovsky
2016-06-02 14:32 ` Jan Beulich
2016-04-06 1:25 ` [PATCH RFC 10/20] acpi/hvmloader: Provide address of acpi_info as an argument to ACPI code Boris Ostrovsky
2016-06-03 16:03 ` Jan Beulich
2016-04-06 1:25 ` [PATCH RFC 11/20] acpi/hvmloader: Translate all addresses when assigning addresses in ACPI tables Boris Ostrovsky
2016-06-06 10:48 ` Jan Beulich
2016-04-06 1:25 ` [PATCH RFC 12/20] acpi/hvmloader: Link ACPI object files directly Boris Ostrovsky
2016-06-06 11:04 ` Jan Beulich
2016-06-06 14:20 ` Boris Ostrovsky
2016-06-06 14:29 ` Jan Beulich
2016-06-06 14:49 ` Boris Ostrovsky
2016-06-06 14:57 ` Jan Beulich
2016-06-06 15:31 ` Andrew Cooper
2016-06-06 15:41 ` Jan Beulich
2016-04-06 1:25 ` [PATCH RFC 13/20] acpi/hvmloader: Add stdio.h, string.h and x86.h Boris Ostrovsky
2016-06-06 11:31 ` Jan Beulich
2016-06-06 15:08 ` Boris Ostrovsky
2016-06-06 15:22 ` Jan Beulich
2016-04-06 1:25 ` [PATCH RFC 14/20] acpi/hvmloader: Replace mem_alloc() and virt_to_phys() with memory ops Boris Ostrovsky
2016-06-06 12:58 ` Jan Beulich
2016-06-06 15:46 ` Boris Ostrovsky
2016-04-06 1:25 ` [PATCH RFC 15/20] acpi: Move ACPI code to xen/common/libacpi Boris Ostrovsky
2016-06-06 13:05 ` Jan Beulich
2016-06-06 16:09 ` Boris Ostrovsky
2016-06-07 6:20 ` Jan Beulich
2016-06-07 12:24 ` Roger Pau Monné
2016-06-07 14:32 ` Boris Ostrovsky
2016-04-06 1:25 ` [PATCH RFC 16/20] x86/vlapic: Don't try to accept 8259 interrupt if !has_vpic() Boris Ostrovsky
2016-06-03 16:14 ` Jan Beulich
2016-06-03 17:50 ` Boris Ostrovsky
2016-04-06 1:25 ` [PATCH RFC 17/20] x86: Allow LAPIC-only emulation_flags for HVM guests Boris Ostrovsky
2016-06-03 16:18 ` Jan Beulich
2016-04-06 1:25 ` [PATCH RFC 18/20] libxc/acpi: Build ACPI tables for HVMlite guests Boris Ostrovsky
2016-06-02 16:26 ` Roger Pau Monné
2016-06-06 12:03 ` Wei Liu
2016-06-06 15:15 ` Boris Ostrovsky
2016-06-16 8:54 ` Wei Liu
2016-06-16 13:07 ` Boris Ostrovsky
2016-06-06 13:29 ` Jan Beulich
2016-06-06 16:59 ` Boris Ostrovsky
2016-06-07 6:17 ` Jan Beulich
2016-06-07 13:59 ` Boris Ostrovsky
2016-06-07 14:10 ` Jan Beulich
2016-06-07 14:47 ` Boris Ostrovsky
2016-06-07 15:00 ` Jan Beulich
2016-04-06 1:25 ` [PATCH RFC 19/20] acpi: Set HW_REDUCED_ACPI in FADT if IOAPIC is not supported Boris Ostrovsky
2016-06-06 13:38 ` Jan Beulich
2016-06-06 17:31 ` Boris Ostrovsky
2016-06-07 6:06 ` Jan Beulich
2016-06-07 14:02 ` Boris Ostrovsky
2016-06-07 14:12 ` Jan Beulich
2016-06-07 15:17 ` Boris Ostrovsky
2016-06-07 15:41 ` Jan Beulich
2016-06-08 22:04 ` Boris Ostrovsky [this message]
2016-06-09 8:13 ` Roger Pau Monné
2016-06-09 8:41 ` Jan Beulich
2016-06-09 14:09 ` Boris Ostrovsky
2016-04-06 1:25 ` [PATCH RFC 20/20] acpi: Make ACPI builder available to hypervisor code Boris Ostrovsky
2016-06-06 13:48 ` Jan Beulich
2016-05-09 20:10 ` [PATCH RFC 00/20] Make ACPI builder available to components other than hvmloader Boris Ostrovsky
2016-05-10 7:25 ` Jan Beulich
2016-06-02 12:40 ` Jan Beulich
2016-06-02 16:37 ` Boris Ostrovsky
2016-06-03 7:18 ` Roger Pau Monné
2016-06-03 10:08 ` Jan Beulich
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