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

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

Carlo Marcelo Arenas Belon wrote:
> Using gcc4 to compile qemu will generate broken code for its cpu emulation
> but should be fine if using kvm only.
>
> This will allow users that have no access to gcc4 on their platforms to at
> least get kvm compiled and use it while preventing them to run a broken
> qemu if kvm is not available.
>   

This is a pretty bad thing IMHO.  There are other patches out there that 
allow QEMU (even with -no-kvm) to work with GCC4.  A random check like 
this is going to result in difficulties down the road.  Maybe a release 
of GCC4 will allow QEMU to work in the future.  A check like this is 
just way too general IMHO.

If you're going to do anything, a firm warning when compiling with a 
GCC4 override would be the best thing.

Regards,

Anthony Liguori

> This is not meant to be used in the long run when a solution to qemu's use
> of gcc-3.x for code generation is finally resolved upstream, which is why
> it is kept inside the KVM specific sections of the code only.
>
> Signed-off-by: Carlo Marcelo Arenas Belon <carenas-kLeDWSohozoJb6fo7hG9ng@public.gmane.org>
> ---
>  qemu/vl.c |   10 ++++++++++
>  1 files changed, 10 insertions(+), 0 deletions(-)
>
> diff --git a/qemu/vl.c b/qemu/vl.c
> index 634fb34..549f008 100644
> --- a/qemu/vl.c
> +++ b/qemu/vl.c
> @@ -8425,8 +8425,13 @@ int main(int argc, char **argv)
>  #endif
>  #ifdef USE_KVM
>  	    case QEMU_OPTION_no_kvm:
> +#if __GNUC__ >= 4
> +		fprintf(stderr, "Can't run without kvm if compiled with gcc4\n");
> +		exit(1);
> +#else
>  		kvm_allowed = 0;
>  		break;
> +#endif
>  	    case QEMU_OPTION_no_kvm_irqchip:
>  		kvm_irqchip = 0;
>  		break;
> @@ -8559,8 +8564,13 @@ int main(int argc, char **argv)
>  #if USE_KVM
>      if (kvm_allowed) {
>  	if (kvm_qemu_init() < 0) {
> +#if __GNUC__ >= 4
> +	    fprintf(stderr, "Could not initialize KVM, can't run without kvm if compiled with gcc4\n");
> +	    exit(1);
> +#else
>  	    fprintf(stderr, "Could not initialize KVM, will disable KVM support\n");
>  	    kvm_allowed = 0;
> +#endif
>  	}
>      }
>  #endif
>   


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