linux-kernel - Re: hardwired VMI crap

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Message-ID: <20070308211306.GA20934@elte.hu>
Date:	Thu, 8 Mar 2007 22:13:06 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Zachary Amsden <zach@...are.com>
Cc:	tglx@...utronix.de, Jeremy Fitzhardinge <jeremy@...p.org>,
	john stultz <johnstul@...ibm.com>, akpm@...ux-foundation.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Pratap Subrahmanyam <pratap@...are.com>,
	Rusty Russell <rusty@...tcorp.com.au>, Andi Kleen <ak@...e.de>,
	Daniel Hecht <dhecht@...are.com>,
	Daniel Arai <arai@...are.com>,
	Chris Wright <chrisw@...s-sol.org>
Subject: Re: hardwired VMI crap

* Zachary Amsden <zach@...are.com> wrote:

> When we're about two weeks away from a product release and you are 
> threatening to unmerge or block our code because we didn't create an 
> abstract interrupt controller, we re-used the APIC and IO-APIC, this 
> is uber rocket science. [...]

see my mail to you below: you've been told about the clockevents problem 
months ago, that you shouldnt hardwire PIT details and that you should 
be registering a clockevents device. You cannot credibly claim that you 
didnt know about this.

> We've been doing things this way, with public patches for over a year, 
> and you've even been CC'd on some of the discussions. [...]

i've specifically objected, numerous times - the result of which was 
that when you submitted it to lkml you didnt Cc: me ;) The VMI crap went 
in 'under the radar' via the x86_64 tree.

> [...]  So it is a little late to tell us - "redesign your hypervisor, 
> or else.."

Also, it was /you/ who claimed that paravirt_ops can take care of 
whatever design change on the Linux side - that claim is apparently 
history now and you are now claiming "there's a product on the road, we 
cannot change the hypervisor ABI"? Should i cite that email of yours 
too?

	Ingo

----------------->
Date: Fri, 5 Jan 2007 06:45:04 +0100
From: Ingo Molnar <mingo@...e.hu>
To: Zachary Amsden <zach@...are.com>
Subject: Re: Clockevent changes in -mm tree
Cc: Thomas Gleixner <tglx@...utronix.de>, Andrew Morton <akpm@...l.org>,
        Rusty Russell <rusty@...tcorp.com.au>

* Zachary Amsden <zach@...are.com> wrote:

> So I'm running into some issues integrating the VMI timer code with 
> the clockevent code in the -mm tree.  Basically, my question is - are 
> clockevents now required to get the timer infrastructure to work 
> properly, and can I have multiple clockevent sources (to allow 
> overriding the PIT) that are selected at boot time?

(I've Cc:-ed Rusty too, the author of the paravirtualization patches. 
Rusty, what's your take on the VMI timer patchset of Zach?)

in any case, i dont see any fundamental problem here. The right model 
for timer paravirtualization is to notify the guest during early bootup 
that this is a paravirtual bootup. Then the guest doesnt even register 
the PIT clocksource but registers the virtual clock-events driver.

	Ingo

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