linux-kernel - Re: [patch] paravirt: VDSO page is essential

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Date:	Mon, 05 Mar 2007 17:03:24 -0800
From:	Zachary Amsden <zach@...are.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Roland McGrath <roland@...hat.com>,
	Andi Kleen <ak@...e.de>,
	virtualization <virtualization@...ts.osdl.org>
Subject: Re: [patch] paravirt: VDSO page is essential

Rusty Russell wrote:
> On Tue, 2007-03-06 at 00:28 +1100, Rusty Russell wrote:
>   
>> On Mon, 2007-03-05 at 13:06 +0100, Ingo Molnar wrote:
>>     
>>> Subject: [patch] paravirt: VDSO page is essential
>>> From: Ingo Molnar <mingo@...e.hu>
>>>
>>> commit 3bbf54725467d604698721384d858b5983b87e8f disables the VDSO for 
>>> CONFIG_PARAVIRT kernels. This #ifdeffery was a bad change: the VDSO is 
>>> an essential component of Linux, and this change forces all of them to 
>>> use int $0x80 - including sane ones like KVM. (If a hypervisor does not 
>>> handle the VDSO properly then it can work things around via the vdso=0 
>>> boot option. Or CONFIG_PARAVIRT should not have been merged. But in any 
>>> case, it is a basic taste issue: we DO NOT #ifdef around core features 
>>> like this!)
>>>       
>> I agree with the criticism, dislike the snarly comments, and disagree
>> with this patch.
>>     
>
> And my patch was pretty crack-induced too.  Sorry.
>
> I shouldn't have been thinking about using CONFIG options at all: we
> should simply disable the vdso if CONFIG_COMPAT_VDSO=y when we
> *actually* reserve top memory.
>
> This still need some work (doing that now), but do people like the idea?
>
> The current "vdso_disabled" flag merely disabled the ELF note, so it
> needs to be made a little stronger, to not set up the vdso at all.
>   

I had just sent this out for internal review...



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