linux-kernel - Re: [PATCH] Add I/O hypercalls for i386 paravirt

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Message-ID: <46CCAD7A.80505@vmware.com>
Date:	Wed, 22 Aug 2007 14:41:14 -0700
From:	Zachary Amsden <zach@...are.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Andi Kleen <ak@...e.de>, Andrew Morton <akpm@...l.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Virtualization Mailing List <virtualization@...ts.osdl.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Chris Wright <chrisw@...s-sol.org>,
	Avi Kivity <avi@...ranet.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>
Subject: Re: [PATCH] Add I/O hypercalls for i386 paravirt

Alan Cox wrote:
>> I still think it's preferable to change some drivers than everybody.
>>
>> AFAIK BusLogic as real hardware is pretty much dead anyways,
>> so you're probably the only primary user of it anyways.
>> Go wild on it!
>>     
>
> I don't believe anyone is materially maintaining the buslogic driver and
> in time its going to break completely.
>   

I think I was actually the last person to touch it ;)

>   
>> Well that might be. I just think it would be a mistake
>> to design paravirt_ops based on someone's short term release engineering
>> considerations.
>>     
>
> Agreed, especially as an interface where each in or out traps into the
> hypervisor is broken even for the model of virtualising hardware. 
>   

Well, it's not necessarily broken, it's just a different model.  At some 
point the cost of maintaining a whole suite of virtual drivers becomes 
greater than leveraging a bunch of legacy drivers.  If you can eliminate 
most of the performance cost of that by changing something at a layer 
below (port I/O), it is a win even if it is not a perfect solution.

But I think I've lost the argument anyways; it doesn't seem to be for 
the greater good of Linux, and there are alternatives we can take.  
Unfortunately for me, they require a lot more work.

Zach
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