Re: Pygrub on ARM64

[Ian Campbell <ian.campbell@citrix.com>]

On Thu, 2016-02-25 at 10:53 +0000, Ian Campbell wrote:
> On Thu, 2016-02-25 at 10:47 +0000, Ian Campbell wrote:
> > 
> > > 
> > > CentOS's first partition is fat to boot on efi systems, but it only
> > > contains the grub efi binary. All the other partitions are xfs. Does
> > > pygrub support it?
> > 
> > I don't know, but pygrub is normally pretty vocal in these situations
> > if it
> > doesn't ("cannot find partition" style message), here it is apparently
> > just
> > silently hanging, which is pretty odd.
> 
> Here is what I get though:
> 
> # wget http://mirror.centos.org/altarch/7/isos/aarch64/CentOS-7-aarch64.i
> mg.xz
> # xz -d CentOS-7-aarch64.img.xz
> # pygrub CentOS-7-aarch64.img 
> Traceback (most recent call last):
>   File "/usr/local/bin/pygrub", line 926, in <module>
>     raise RuntimeError, "Unable to find partition containing kernel"
> RuntimeError: Unable to find partition containing kernel
> 
> Which is much more like what I would normally expect (and matches your
> description of the image layout  think).
> 
> That was on a random x86_64 test box because that was all I had to hand,
> but I'd be pretty surprised if something like this behaved very
> differently on arm64. 

But running on both arm32 arm64 it does indeed spin taking 100% of the CPU.

My guess would be a bug in the file system parsing code, perhaps something
to do with alignment, which results in an infinite loop. The libfsimage
backends originally came from grub (1/legacy) and is therefore only really
has history on x86.

We certainly test pygrub on arm32 regularly, and I am sure it must have
worked on arm64 when I was adding arm64 support to osstest (which is
_still_ pending h/w to go into the colo!), so the basics (i..e simple
partition tables with ext* partitions) must be ok, so I would hazzard a
stab in the dark that the issue is in one of the things specific to these
images, i.e. either the FAT or the XFS backend (if there even is an XFS
backend, I didn't check).

Ian.


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