linux-kernel - Re: [PATCH v3 2/3] ACPI / OSL: Allow PCI to be disabled

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Date:   Tue, 11 Dec 2018 16:57:32 -0500
From:   Sinan Kaya <okaya@...nel.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/3] ACPI / OSL: Allow PCI to be disabled

On 12/11/2018 4:46 PM, Rafael J. Wysocki wrote:
> On Tue, Dec 11, 2018 at 6:37 PM Sinan Kaya <okaya@...nel.org> wrote:
>>
>> On 12/11/2018 12:09 PM, Christoph Hellwig wrote:
>>> On Mon, Dec 10, 2018 at 06:13:14PM +0000, Sinan Kaya wrote:
>>>> Getting ready to allow PCI to be disabled with ACPI enabled. Stub
>>>> out calls that depend on PCI.
>>>
>>> I think you want to skip building at least all of hwpci.c if CONFIG_PCI
>>> is disabled.  Or replace that whole stiking pile of crap with something
>>> resembling C code..
>>>
>>
>> I can give it a try but I'm under the impression that we don't touch
>> ACPICA code in general.
>>
>> Feel free to correct me.
> 
> We don't as a rule, but depending on what the patch looks like, we
> might not follow the rule this time.
> 

OK. Good to know. I'll take a stab at it.

> I wonder though what we do if some AML wants to access PCI config
> space via an opregion in there.  Have you thought about that?
> 

Return an error.

AFAIK, ACPI spec says that AML code running on non-existing op-regions to be
discarded last time I checked.

I know Linux is noisy about these.

I did boot QEMU without CONFIG_PCI. There was a bunch of ACPI errors reported
during boot as expected but boot succeeded. There was no hard lockup/failure.