Re: [Xen-users] Extra Probes on xl create

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2012-05-31 at 02:32 +0100, Ian wrote:
> On 30/05/12 06:44, Ian Campbell wrote:
> > On Wed, 2012-05-30 at 01:15 +0100, Ian wrote:
> >> Hi All,
> >>
> >> I have two Xen machines, both running 4.12 compiled from source. One is
> >> running SL6.2 with a kernel compiled from vanilla source (3.2.0) and the
> >> second is using the stock kernel from Ubuntu (3.2.0-23-generic).
> >>
> >> I moved a pv CentOS 5.8 vm from the SL machine to the Ubuntu machine and
> >> noticed a difference when starting (i.e. an error)
> >>
> >> "xl -v create" gives...
> >>
> >>
> >> SL 6.2
> >>
> >> domainbuilder: detail: xc_dom_allocate: cmdline="ro root=LABEL=/
> >> console=xvc0 ", features="(null)"
> >> domainbuilder: detail: xc_dom_kernel_mem: called
> >> domainbuilder: detail: xc_dom_malloc            : 10836 kB
> >> domainbuilder: detail: xc_dom_do_gunzip: unzip ok, 0x21bbf4 ->  0xa952d8
> >> domainbuilder: detail: xc_dom_ramdisk_mem: called
> >> domainbuilder: detail: xc_dom_boot_xen_init: ver 4.1, caps
> >> xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p
> >> hvm-3.0-x86_64
> >> domainbuilder: detail: xc_dom_parse_image: called
> >> domainbuilder: detail: xc_dom_find_loader: trying ELF-generic loader ...
> >> domainbuilder: detail: loader probe OK
> >>
> >> Ubuntu 12.04
> >>
> >> domainbuilder: detail: xc_dom_allocate: cmdline="ro root=LABEL=/
> >> console=xvc0 ", features="(null)"
> >> domainbuilder: detail: xc_dom_kernel_mem: called
> >> domainbuilder: detail: xc_dom_malloc            : 10836 kB
> >> domainbuilder: detail: xc_dom_do_gunzip: unzip ok, 0x21bbf4 ->  0xa952d8
> >> domainbuilder: detail: xc_dom_ramdisk_mem: called
> >> domainbuilder: detail: xc_dom_boot_xen_init: ver 4.1, caps
> >> xen-3.0-x86_64 xen-3.0-x86_32p
> >> domainbuilder: detail: xc_dom_parse_image: called
> >> domainbuilder: detail: xc_dom_find_loader: trying multiboot-binary
> >> loader ...
> >> domainbuilder: detail: loader probe failed
> >> domainbuilder: detail: xc_dom_find_loader: trying Linux bzImage loader ...
> >> xc: error: panic: xc_dom_bzimageloader.c:556:
> >> xc_dom_probe_bzimage_kernel: kernel is not a bzImage: Invalid kernel
> >> domainbuilder: detail: loader probe failed
> >> domainbuilder: detail: xc_dom_find_loader: trying ELF-generic loader ...
> >> domainbuilder: detail: loader probe OK
> >>
> >>
> >> Both boot fine, and it looks like the Ubuntu version is trying to do
> >> something extra. I googled the error message and I am not concerned
> >> about it as it appears to be a spurious error caused by an extra probe.
> >
> After further digging, it would seem that the SL machine was performing 
> the same actions. Further digging in the source code suggests that the 
> loaders are "pluggable" and are "registered". Fair to say that for some 
> reason, they are registered in a different order on the different 
> machines. Most of this stretches my limited understanding of C and I am 
> not figuring out how the ordering of the registration is done. Maybe the 
> compiler, maybe make.

Right.

> I am starting to think this isn't worth worrying about.

I agree, it's not.

Ian.



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