On 11/28/25 08:49, Ritesh Harjani (IBM) wrote:

"David Hildenbrand (Red Hat)" [off-list ref] writes:

quoted

On 11/28/25 06:05, Ritesh Harjani (IBM) wrote:

quoted

"David Hildenbrand (Red Hat)" [off-list ref] writes:

quoted

On 10/21/25 12:06, David Hildenbrand wrote:

quoted

Two smaller fixes identified while doing a bigger rework.

Compile-tested only as I don't have an easy way to test right now.

I would prefer for these patches to go through the MM tree as I will
be sending out a bigger version soon that is based on this series --
I split of the fixes from the other stuff.

Ping,

I tried to get CMM running again (using the simulation mode I introduced
a while back), but so far my attempts to get a reasonable powernv VM
booted in QEMU failed :(

(e.g., Fedora qcow2 images use xfs, but the open powernv loader is based
on a 5.10 kernel without some mystical XFS feature ...)

Hi Ritesh,

quoted

Sorry, I missed seeing this earlier.

Do you have the link to simulation mode which you are referring above
please? So far I didn't find the support of this beyond Linux LPAR
(pseries), but maybe I missed it.

When I did a rework of the CMM balloon in 2019, I needed a way to test
it. So I added

commit b1713975c31ae20ecc40fd00191ee3fa51445d4a
Author: David Hildenbrand [off-list ref]
Date:   Thu Oct 31 15:29:31 2019 +0100

      powerpc/pseries/cmm: Simulation mode

aah right. I should have looked closely. I was thinking you meant
somewhere in Qemu, so I was only looking there.

quoted

      
      Let's allow to test the implementation without needing HW support.
      When "simulate=1" is specified when loading the module, we bypass all
      HW checks and HW calls. The sysfs file "simulate_loan_target_kb" can
      be used to simulate HW requests.
      
      The simualtion mode can be activated using:
        modprobe cmm debug=1 simulate=1
      
      And the requested loan target can be changed using:
        echo X > /sys/devices/system/cmm/cmm0/simulate_loan_target_kb


I allows for bypassing the absence of FW_FEATURE_CMO.

Right. Let me give it a try first with pseries Qemu. Otherwise I have an
access to pseries LPAR too. I can verify it there.

Ah, now I realize my problem: I tried with Fedora 43 in a powerpc VM but 
the modprobe didn't do anything.

Looking again:

# grep CONFIG_CMM /boot/config-6.17.1-300.fc43.ppc64le
CONFIG_CMM=y

So modprob'ing won't do as the module is built in.

Anyhow, compiling a kernel inside a QEMU VM might take a while, so if 
you can beat me to it I wouldn't be mad :)


Re powernv vs. powerpc: yeah, it's confusing. For some reason I thought 
I tested it in the days on powernv. Maybe that's simply because I was 
only able to get my hands on such a machine. Looking again, it should 
indeed be able to be simulated on a simple powerpc VM.

-- 
Cheers

David