linux-kernel - Re: [PATCH 1/3] acpi/processor: fix evaluating

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Message-ID: <Y4opuLnLIT3v9Aa7@Air-de-Roger>
Date:   Fri, 2 Dec 2022 17:37:12 +0100
From:   Roger Pau Monné <roger.pau@...rix.com>
To:     Dave Hansen <dave.hansen@...el.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        jgross@...e.com, Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Len Brown <lenb@...nel.org>,
        Alex Chiang <achiang@...com>,
        Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
        linux-acpi@...r.kernel.org
Subject: Re: [PATCH 1/3] acpi/processor: fix evaluating _PDC method when
 running as Xen dom0

On Fri, Dec 02, 2022 at 08:17:56AM -0800, Dave Hansen wrote:
> On 12/2/22 04:24, Roger Pau Monné wrote:
> > On the implementation side, is the proposed approach acceptable?
> > Mostly asking because it adds Xen conditionals to otherwise generic
> > ACPI code.
> 
> That's a good Rafael question.
> 
> But, how do other places in the ACPI code handle things like this?

Hm, I don't know of other places in the Xen case, the only resource
in ACPI AML tables managed by Xen are Processor objects/devices AFAIK.
The rest of devices are fully managed by the dom0 guest.

I think such special handling is very specific to Xen, but maybe I'm
wrong and there are similar existing cases in ACPI code already.

We could add some kind of hook (iow: a function pointer in some struct
that could be filled on a implementation basis?) but I didn't want
overengineering this if adding a conditional was deemed OK.

Thanks, Roger.