[dm-devel] dm-verity with GPT

[Mikulas Patocka]

On Sat, 17 Sep 2022, Pra.. Dew.. wrote:

> 
> We have a scenario for a VM where a VM is running in the host Linux 
> using KVM. We want to expose verity protected rootfs to the VM. This 
> rootfs clearly needs to be RO. However, we also want to expose it as a 
> GPT partition. In order to do this we are attaching two small files 
> before and after the rootfs. The files use linear mapping and get mapped 
> to the same /dev/mapper/XX device that has a verity partition. These two 
> files contain the partition mappings (primary and backup) for GPT. From 
> the VMs perspective, it sees one device (/dev/mapper/xx) as a GPT device 
> with rootfs.
> 
> The challenge we are getting into is that dm-verity kernel 
> implementation explicitly prohibits mixing linear and verity mapping and 
> forces the /dev/mapper/xx device to be RO and our needs are exactly the 
> opposite.
> 
> Has anyone seen this scenario before? Any suggestions?
> 
> Thanks

Hi

I think that you can create dm-verity target, put dm-linear on the top of 
it and insert that dm-linear into the table with the other two dm-linear 
targets.

Would it work this way?

Mikulas