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

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Message-ID: <20160225081044.GA11372@gmail.com>
Date:	Thu, 25 Feb 2016 09:10:44 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Xen Devel <xen-devel@...ts.xensource.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"Luis R. Rodriguez" <mcgrof@...nel.org>, lguest@...ts.ozlabs.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Borislav Petkov <bp@...en8.de>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	X86 ML <x86@...nel.org>, Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v3 01/11] x86/boot: enumerate documentation for the x86
 hardware_subarch


* Andy Lutomirski <luto@...capital.net> wrote:

> On Feb 24, 2016 12:33 AM, "Ingo Molnar" <mingo@...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;
> >
> 
> Don't we unconditionally remap the IDT?  I think Kees did it for
> general purpose hardening due to our complete inability to hide the
> IDT address. I.e. I think we can remove the f00f condition entirely.

Yeah, indeed - I only judged by the (limited) patch context and assumed the Xen 
problem was with IDT remapping.

But what the quirk really does is only to avoid printing the f00f workaround - 
i.e. a cosmetic change. I think we should just drop the paravirt_enabled() check.

Thanks,

	Ingo