Re: [PATCH 3/5] libxc: create unmapped initrd in domain builder if supported

[Julien Grall <julien.grall@citrix.com>]

On 11/09/15 13:54, Ian Jackson wrote:
> Juergen Gross writes ("[PATCH 3/5] libxc: create unmapped initrd in domain builder if supported"):
>> In case the kernel of a new pv-domU indicates it is supporting an
>> unmapped initrd, don't waste precious virtual space for the initrd,
>> but allocate only guest physical memory for it.
> ...
> 
> The name of this ELFNOTE suggests that it applies to all multiboot
> modules, not just ramdisks.  In particular, that means perhaps it
> ought to apply to device tree blobs too ?

The device tree blobs is not a multiboot module but directly pass in a
register to the kernel.

FWIW, we don't have any ELF support right now on ARM.

>> -    /* load ramdisk */
>> -    if ( dom->ramdisk_blob )
>> +    /* Load ramdisk if initial mapping required. */
>> +    if ( dom->ramdisk_blob &&
>> +         (!dom->parms.elf_notes[XEN_ELFNOTE_MOD_START_PFN].data.num ||
>> +          dom->ramdisk_seg.vstart) )
> 
> After this patch the resulting structure of the code is rather
> unfortunate, in that the order of the main processing steps depends on
> this ELFNOTE.

Shouldn't we ought to have a common code ELF agnostic? I.e we may have
other kernel image format where we have notes but not ELF notes.

Regards,

-- 
Julien Grall