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Thu, 27 Nov 2025 23:57:00 -0800 (PST) Received: from dw-tp ([49.207.234.175]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7d151eb5bd9sm4110823b3a.27.2025.11.27.23.56.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Nov 2025 23:56:59 -0800 (PST) From: Ritesh Harjani (IBM) To: "David Hildenbrand (Red Hat)" , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, Andrew Morton , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy Subject: Re: [PATCH v1 0/2] powerpc/pseries/cmm: two smaller fixes In-Reply-To: <3cc7d401-c77c-4ac8-abb8-c264fbd9aaf0@kernel.org> Date: Fri, 28 Nov 2025 13:19:08 +0530 Message-ID: <87y0nqmwaz.ritesh.list@gmail.com> References: <20251021100606.148294-1-david@redhat.com> <557b5500-412a-4d26-8c4b-147c9a00d5fd@kernel.org> <87zf86n3vq.ritesh.list@gmail.com> <3cc7d401-c77c-4ac8-abb8-c264fbd9aaf0@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: "David Hildenbrand (Red Hat)" writes: > On 11/28/25 06:05, Ritesh Harjani (IBM) wrote: >> "David Hildenbrand (Red Hat)" 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 > 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. > > 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. > Back in the days I was able to test it with a pseries (or was it powernv?) Agree the name can be a bit confusing. So powernv == Power Non-Virtualized that's the baremetal Power box. pseries == is basically the Linux LPAR on PowerVM. Qemu/KVM also has support for booting Linux pseries guest. > machine we had here at RH. So far my attempts failed to test it in a > similar fashion in QEMU. > Let me give it a try and I will update how it goes. Thanks! -ritesh