Re: [patch 14/21] Xen-paravirt: Add XEN config options and disable unsupported config options.

From: Dan Hecht <dhecht@vmware.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Andi Kleen <ak@muc.de>, Andrew Morton <akpm@osdl.org>,
	virtualization@lists.osdl.org, xen-devel@lists.xensource.com,
	Chris Wright <chrisw@sous-sol.org>,
	Ian Pratt <ian.pratt@xensource.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [patch 14/21] Xen-paravirt: Add XEN config options and disable unsupported config options.
Date: Tue, 13 Feb 2007 15:58:50 -0800	[thread overview]
Message-ID: <45D250BA.7010104@vmware.com> (raw)
In-Reply-To: <45D249D9.80407@goop.org>

On 02/13/2007 03:29 PM, Jeremy Fitzhardinge wrote:
> Dan Hecht wrote:
>> I assume you plan to eventually get all this stuff working but just
>> want to prevent configurations that the Xen paravirt-ops isn't ready
>> for at the moment?
>>
>> Instead can you do it this way:
>>
>> config XEN
>>     depends on PARAVIRT && !PREEMPT && HZ_100 && !DOUBLEFAULT && !KEXEC
> 
> That's a bit simpler code-wise, but it does make it pretty complex to
> get everything just-so to even see the CONFIG_XEN option.
> 

Not only is it simpler code-wise, but it is more to the point... it is 
CONFIG_XEN that needs to be fixed to handle PREEMPT, KEXEC, different HZ 
values, etc.  Not the other way around.

Enabling the compile of any paravirt-ops backend shouldn't cripple the 
kernel in any way... instead, the burden should be on the xen 
paravirt-ops backend to be completed.  CONFIG_PREEMPT shouldn't care 
about which paravirt-ops are compiled in.  Instead, CONFIG_XEN is the 
one that needs !PREEMPT.

Dan