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

Zachary Amsden
2007-02-13T23:58:22Z

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.
>

Yes, but that is what you need to do to compile Xen - logically, to
build a Xen kernel, you need to have a kernel configuration which can
enable Xen - not limit the configuration of a kernel because Xen has
been enabled. This is because with paravirt-ops, Xen compiled kernels
may not actually run on Xen, so you can't arbitrarily drop features
because you assume Xen is there.

One of these has an easy solution - doublefault. You don't need to
install the doublefault gate if you don't want it, and the hypervisor
doesn't need to freak out if you install it, it can just ignore the gate
entirely and claim #DF is not supported.

Zach