[Pkg-xen-devel] Bug#994870: Bug#994870: Memory allocation problem for VM after xen security update

[Andy Smith]

Hello,

On Fri, Sep 24, 2021 at 03:33:21PM +0200, Hans van Kranenburg wrote:
> The smallest amount of work to initially get your VM going again is to
> only install the 64 bit kernel and keep running a 32 bit user land.

Yep, I have a few 32-bit PV domUs that I run as 64-bit just the
kernel, works great.

> The process to fully change from a 32 to 64 system (in place) is called
> 'cross grading'. I found instructions at
> https://wiki.debian.org/CrossGrading
> 
> I never did this myself, though.

I've done it lots of times but for any non-trivial host you have to
pretty much be a Debian expert to know how to handle the many
problems that dpkg will encounter. It takes longer than
reinstalling and a mistake breaks everything. Not recommended.

> It should be as simple as changing type="pv" to type="pvh" in the config
> file. In Debian, using PVH this is possible since Buster. Also, using
> the xen variant of grub2 (grub-xen and grub-xen-host) is possible.

I can confirm that I have a lot of Debian stretch domUs running PVH
but you do need to install backports kernel in the domU. The 4.9.x
stretch kernelis too old. You need the 4.19.x one from
stretch-backports. They boot fine for me with pvhgrub.

Cheers,
Andy