Re: [PATCH] Abort if gcc4 was used to compile qemu and kvm is not enabled

[Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org>]

Byron Stanoszek wrote:
> On Mon, 8 Oct 2007, Anthony Liguori wrote:
>>
>> If you're going to do anything, a firm warning when compiling with a
>> GCC4 override would be the best thing.
>
> I disagree with the compile warning. There have been times in the past 
> when
> I've forgotten to "insmod kvm*.ko" long after the compile stage, and 
> wound up
> wondering why the virtual machine was slower. Even when I first 
> started using
> KVM, I had no positive feedback that KVM was even working properly 
> (was the
> device node created? am I using a cpu with the correct extensions? 
> etc). I
> eventually figured out that if 'lsmod' showed kvm-intel.ko usage > 0, 
> then I
> knew it was working.

You don't have to have kvm.ko insmod'd during compile.  Presumably the 
issue you were seeing is that you built a version of QEMU without KVM 
support.  Were you using the top-level configure script?

> I would think that anyone who is using KVM has the required hardware 
> and wants
> to be sure that KVM is really being used. Specifying -no-kvm is an 
> excellent
> tool for debugging purposes, but I don't want KVM to fail silently on 
> me and
> pretend that I typed -no-kvm, especially if I'm using GCC 4.x and never
> intended to use the QEMU portion anyway.

Eventually, KVM will merge with upstream QEMU.  In that case, many 
people will be using QEMU without the desiring to use KVM.  We don't 
want to introduce behavior in QEMU that is unmergable with upstream QEMU 
b/c that will just cause users more headache when that behavior is 
eventually change.

Regards,

Anthony Liguori

> I would much rather see KVM fail gracefully, rather than revert to QEMU,
> regardless of the compiler version being used.
>
>  -Byron
>
> -- 
> Byron Stanoszek                         Ph: (330) 644-3059
> Systems Programmer                      Fax: (330) 644-8110
> Commercial Timesharing Inc.             Email: byron-vdaza9t/se1BDgjK7y7TUQ@public.gmane.org
>


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