linux-kernel - Re: [PATCH] x86: Bypass legacy PIC and PIT on ACPI hardware reduced platform

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Date:	Wed, 04 Mar 2015 15:16:07 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>,
	"Li, Aubrey" <aubrey.li@...ux.intel.com>,
	"alan@...ux.intel.com" <alan@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Len.Brown@...el.com,
	x86@...nel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: Bypass legacy PIC and PIT on ACPI hardware reduced platform

On Wednesday, March 04, 2015 10:50:11 AM Borislav Petkov wrote:
> On Wed, Mar 04, 2015 at 12:43:08AM -0800, Arjan van de Ven wrote:
> > >
> > >Using 'acpi_gbl_reduced_hardware' flag outside the ACPI code
> > >is a mistake.
> > 
> > ideally, the presence of that flag in the firmware table will clear/set more global settings,
> > for example, having that flag should cause the 8042 input code to not probe for the 8042.
> > 
> > for interrupts, there really ought to be a "apic first/only" mode, which is then used on
> > all modern systems (not just hw reduced).
> 
> Do we need some sort of platform-specific querying interfaces now too,
> similar to cpu_has()? I.e., platform_has()...
> 
> 	if (platform_has(X86_PLATFORM_REDUCED_HW))
> 		do stuff..
> 
> Hmmm.

Sort of.  What we need is a "do not touch PIC/PIT" bit for the code that
tries to fall back to them in some cases (which may appear to work if
the hardware is physically there, but it may confuse the platform).


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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