linux-kernel - Re: [PATCH v3 01/11] x86/boot: enumerate documentation for the x86 hardware

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Date:	Thu, 7 Apr 2016 22:59:02 +0200
From:	"Luis R. Rodriguez" <mcgrof@...e.com>
To:	Ingo Molnar <mingo@...nel.org>,
	David Vrabel <david.vrabel@...rix.com>
Cc:	"Luis R. Rodriguez" <mcgrof@...nel.org>, bp@...en8.de,
	hpa@...or.com, tglx@...utronix.de, mingo@...hat.com,
	rusty@...tcorp.com.au, x86@...nel.org,
	linux-kernel@...r.kernel.org, luto@...capital.net,
	boris.ostrovsky@...cle.com, david.vrabel@...rix.com,
	konrad.wilk@...cle.com, xen-devel@...ts.xensource.com,
	lguest@...ts.ozlabs.org,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 01/11] x86/boot: enumerate documentation for the x86
 hardware_subarch

David, please note below the highlighted code.

On Wed, Feb 24, 2016 at 09:32:59AM +0100, Ingo Molnar wrote:
> 
> * Luis R. Rodriguez <mcgrof@...nel.org> wrote:
> For hard coded platform quirks I'd suggest we add x86_platform.quirks flags. For 
> example the F00F hack for Xen could be done via:
> 
> 	x86_platform.quirks.idt_remap = 0;
> 
> and would be set like this during early init:
> 
> void early_init_platform_quirks(void)
> {
> 	x86_platform.legacy.ebda_search = 0;
> 	x86_platform.quirks.idt_remap = 1;
> 
> 	switch (boot_params.hdr.hardware_subarch) {
> 		case X86_SUBARCH_PC:
> 			x86_platform.legacy.ebda_search = 1;
> 			break;
> 		case X86_SUBARCH_XEN:
> 			x86_platform.quirks.idt_remap = 0;
> 			break;
> 		case X86_SUBARCH_LGUEST:
> 			x86_platform.quirks.idt_remap = 0;
> 			break;
> 	}
> }
> 
> And if also add the legacy RTC flag, it becomes:
> 
> void early_init_hardcoded_platform_quirks(void)
> {
> 	x86_platform.legacy.ebda_search = 0;
> 	x86_platform.quirks.idt_remap = 1;
> 	x86_platform.legacy.rtc = 1;
> 
> 	switch (boot_params.hdr.hardware_subarch) {
> 		case X86_SUBARCH_PC:
> 			x86_platform.legacy.ebda_search = 1;
> 			break;
> 		case X86_SUBARCH_XEN:
> 			x86_platform.quirks.idt_remap = 0;
> 			x86_platform.legacy.rtc = 0;
> 			break;
> 		case X86_SUBARCH_LGUEST:
> 			x86_platform.quirks.idt_remap = 0;
> 			x86_platform.legacy.rtc = 0;
> 			break;
> 	}
> }
> 
> Note that both opt-in and opt-out quirks/legacies are possible this way, and note 
> how cleanly and consistently it's all organized: setup of all hard coded 
> legacies/quirks is concentrated in a single function, and the actual usage sites 
> don't know anything about subarchitectures.

<-- snip -- > 

So.. I went with Ingo's template.

> Furthermore we should probably move a few other existing legacies to this flag 
> space as well, to make all this more consistent.

And this suggestion should explain a bit of the effort I put into making
room for other legacy things, which I'll elaborate in the other thread.

  Luis