Re: [kvm-unit-tests PATCH v7 3/8] s390x: sie: switch to home space mode before entering SIE

[Janosch Frank <frankja@linux.ibm.com>]

On 11/3/23 10:29, Nico Boehr wrote:
> This is to prepare for running guests without MSO/MSL, which is
> currently not possible.
> 
> We already have code in sie64a to setup a guest primary ASCE before
> entering SIE, so we can in theory switch to the page tables which
> translate gpa to hpa.
> 
> But the host is running in primary space mode already, so changing the
> primary ASCE before entering SIE will also affect the host's code and
> data.
> 
> To make this switch useful, the host should run in a different address
> space mode. Hence, set up and change to home address space mode before
> installing the guest ASCE.
> 
> The home space ASCE is just copied over from the primary space ASCE, so
> no functional change is intended, also for tests that want to use
> MSO/MSL. If a test intends to use a different primary space ASCE, it can
> now just set the guest.asce in the save_area.
> 
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> Reviewed-by: Thomas Huth <thuth@redhat.com>

Reviewed-by: Janosch Frank <frankja@linux.ibm.com>