Re: [PATCH v1 0/2] powerpc/pseries/cmm: two smaller fixes
From: David Hildenbrand (Red Hat)
Date: Fri Nov 28 2025 - 02:36:11 EST
On 11/28/25 06:05, Ritesh Harjani (IBM) wrote:
"David Hildenbrand (Red Hat)" <david@xxxxxxxxxx> writes:
On 10/21/25 12:06, David Hildenbrand wrote:
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,
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 <david@xxxxxxxxxx>
Date: Thu Oct 31 15:29:31 2019 +0100
powerpc/pseries/cmm: Simulation mode
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.
Back in the days I was able to test it with a pseries (or was it powernv?)
machine we had here at RH. So far my attempts failed to test it in a
similar fashion in QEMU.
--
Cheers
David