Subject: Re: [PATCH 9/11] Panic delay fix
From: Rusty Russell <rusty@rustcorp.com.au>
To: Pavel Machek <pavel@ucw.cz>
Cc: Zachary Amsden <zach@vmware.com>, Andi Kleen <ak@muc.de>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>, Jeremy Fitzhardinge <jeremy@goop.org>,
       Chris Wright <chrisw@sous-sol.org>
In-Reply-To: <20070207123552.GD4481@ucw.cz>
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	 <20070207123552.GD4481@ucw.cz>
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Date: Thu, 08 Feb 2007 07:36:12 +1100
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On Wed, 2007-02-07 at 12:35 +0000, Pavel Machek wrote:
> Ugh, it sounds like paravirt is more b0rken then I thought. It should
> always to the proper delay, then replace those udelays that are not
> needed on virtualized hardware with something else.
> 
> Just magically defining udelay into nop is broken.

We'd have to audit and figure out what udelays are for hardware and
which are not, but the evidence is that the vast majority of them are
for hardware and not needed for virtualization.

Changing udelay to "hardware_udelay" or something all over the kernel
would have delayed the paravirt_ops merge by an infinite amount 8)

Rusty.

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