linux-kernel - Re: [PATCH v2 3/3] paravirt: rename paravirt_enabled to paravirt

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Date:	Wed, 17 Feb 2016 16:21:56 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Borislav Petkov <bp@...en8.de>,
	"Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Andy Lutomirski <luto@...capital.net>,
	Juergen Gross <jgross@...e.com>,
	Michael Brown <mcb30@...e.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Joerg Roedel <joro@...tes.org>,
	Robert Moore <robert.moore@...el.com>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Xen Devel <xen-devel@...ts.xensource.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Jan Beulich <JBeulich@...e.com>, Lv Zheng <lv.zheng@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	long.wanglong@...wei.com, Fengguang Wu <fengguang.wu@...el.com>,
	qiuxishi@...wei.com, Andrey Ryabinin <ryabinin.a.a@...il.com>,
	david.e.box@...el.com, X86 ML <x86@...nel.org>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v2 3/3] paravirt: rename paravirt_enabled to
 paravirt_legacy

On 02/17/2016 03:49 PM, Borislav Petkov wrote:
> On Wed, Feb 17, 2016 at 12:07:13PM -0800, Luis R. Rodriguez wrote:
>> OK so here's a wiki to keep track of progress of the difference uses:
>>
>> http://kernelnewbies.org/KernelProjects/remove-paravirt-enabled
>>
>> It seems we have a resolution one way or another for all except for
>> the use on arch/x86/mm/dump_pagetables.c, is that right?
>
> Why not?
>
> I think we should simply check the range as ffff800000000000 -
> ffff87ffffffffff is practically an ABI and nothing should be mapped
                                                     ^^^^^^^^^

That's exactly the point: if something is mapped it's an error for a 
non-PV kernel.

By removing paravirt_enabled() we may miss those errors. Worse, I think 
we may even crash while doing pagetable walk (although it's probably 
better to crash here than to use an unexpected translation in real code 
somewhere)

-boris


> there anyway. No need for paravirt_enabled() there either.
>