Re: [PATCH] remove dependency on /boot/config-* in grub.d/20_linux_xen

["Vladimir 'φ-coder/phcoder' Serbinenko" <phcoder@gmail.com>]

On 15.07.2013 20:00, Konrad Rzeszutek Wilk wrote:
> Hey,
>
> There is a discussion on the linux-kernel mailing list in which the
> Linus states that "if you depend on any config file, you're broken
> by definition" (https://lkml.org/lkml/2013/7/15/368).
>
The world is broken by definition sometimes you just can't avoid being 
broken unless a good facility for your needs is supplied. In this case 
it would be a documentation on how to detect dom0 pv_ops. We could ship 
a detector as a GRUB tool if appropriate documentation is provided.
> The 20_linux_xen does that however it should not do it. In all fairness
> this check is a bit of old as pretty much any upstream kernel
> is being built by default from distros to boot with Xen. If it does
> not, Xen will print a message telling the user that Linux does not
> have the required components.
>
It depends on kernel config. Not everybody uses one-size-fits-all major 
distro kernels (no offense for distros but sometimes you need or prefer 
customized kernels).
What happens if one tries to load a kernel without pv_ops on top of xen? 
Does he at least get a decent error message or just black screen?
Some distros increase xen_linux priority above those of standard linux 
and it may happen that xen is inadvertently installed but no pv_ops 
kernel is available. With proposed change such setup becomes needlessly 
unbootable.
> This patch removes said check.
>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>
> === modified file 'util/grub.d/20_linux_xen.in'
> --- util/grub.d/20_linux_xen.in	2013-03-24 13:03:33 +0000
> +++ util/grub.d/20_linux_xen.in	2013-07-15 17:34:32 +0000
> @@ -144,20 +144,8 @@
>   }
>
>   linux_list=`for i in /boot/vmlinu[xz]-* /vmlinu[xz]-* /boot/kernel-*; do
> -    if grub_file_is_not_garbage "$i"; then
> -    	basename=$(basename $i)
> -	version=$(echo $basename | sed -e "s,^[^0-9]*-,,g")
> -	dirname=$(dirname $i)
> -	config=
> -	for j in "${dirname}/config-${version}" "${dirname}/config-${alt_version}" "/etc/kernels/kernel-config-${version}" ; do
> -	    if test -e "${j}" ; then
> -		config="${j}"
> -		break
> -	    fi
> -	done
> -        if (grep -qx "CONFIG_XEN_DOM0=y" "${config}" 2> /dev/null || grep -qx "CONFIG_XEN_PRIVILEGED_GUEST=y" "${config}" 2> /dev/null); then echo -n "$i " ; fi
> -    fi
> -    done`
> +    if grub_file_is_not_garbage "$i"; then echo -n "$i "; fi
> +	    done`
>   if [ "x${linux_list}" = "x" ] ; then
>       exit 0
>   fi
>
>
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