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

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Date:	Wed, 04 Mar 2015 06:36:56 -0800
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	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>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>, 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 3/4/2015 1:50 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..

more like

platform_has(X86_PLATFORM_PIT)

etc, one for each legacy io item

so we can clear it on hw reduced, but also in other cases.
hw reduced is one way, but I'd be surprised if there weren't other ways (like quirks)
where we'd want to do the same things



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