Re: [Xen-devel] [RFC PATCH V3 1/2] xen: pass kernel initrd to qemu

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2014-06-23 at 15:22 +0100, Ian Jackson wrote:
> > +/*
> > + * LIBXL_HAVE_BUILDINFO_HVM_DIRECT_KERNEL_BOOT
> > + *
> > + * If this is defined, then the libxl_domain_build_info structure will
> > + * contain hvm.kernel, hvm.cmdline and hvm.ramdisk. hvm.kernel is a string
> > + * to indicate kernel image location, hvm.ramdisk is a string to indicate
> > + * ramdisk location, hvm.cmdline is a string to indicate the paramters 
> > which
> > + * would be appened to kernel image.
> 
> If we are going to do this then I think the kernel, cmdline and
> ramdisk (and bootloader) parameters shoudl be moved into the main part
> of the domain_build_info struct.  This will involve a compatibility
> layer: temporarily (for at least one release)

I don't think so -- we would need to retain it forever or at least until
some sort of "API break" event. We still guarantee that applications
using the 4.2 API will be supported.

>  both will be supported
> so the IDL will have to have both and code inside libxl will have to
> honour either.
> 
> The #define should then be
>   LIBXL_HAVE_BUILD_INFO_CMDLINE
> or some such - because all libxl callers will want to update to the
>   new API eventually.
> 
> > +static char *parse_cmdline(XLU_Config *config)
> > +{
> > +    char *cmdline = NULL;
> > +    const char *root = NULL, *extra = NULL, *buf = NULL;
> > +
> > +    xlu_cfg_get_string (config, "cmdline", &buf, 0);
> > +    xlu_cfg_get_string (config, "root", &root, 0);
> > +    xlu_cfg_get_string (config, "extra", &extra, 0);
> > +
> > +    if (buf) {
> > +        cmdline = strdup(buf);
> > +        if (root || extra)
> > +            fprintf(stderr, "Warning: ignoring deprecated root= and extra= 
> > "
> > +                    "in favour of cmdline=\n");
> 
> Why are you deprecating root= and extra= ?

I suggested this. They are suckful interfaces which expose Linux
specifics (e.g. the root= syntax) in our guest cfg files. cmdline is the
generic equivalent.

However, I didn't mean for them to not work, just that cmdline would be
preferred.

> They seem likely to be a useful distinction if we decide to add
> further default options in the future.
> 
> If you do want to deprecate them, you should make this very clear -
> probably by putting that change in a separate patch in your series.
> 
> Thanks,
> Ian.



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