Gautam Menghani <[email protected]> writes: > On Fri, Jun 05, 2026 at 12:55:50PM +0530, Vaibhav Jain wrote: >> Hi Gautam, >> >> Thanks for testing this patch. Few questions: >> Gautam Menghani <[email protected]> writes: >> >> > On Wed, Jun 03, 2026 at 07:45:39PM +0530, Amit Machhiwal wrote: >> >> On IBM POWER systems, newer processor generations can operate in >> >> compatibility modes corresponding to earlier generations. This becomes >> >> relevant for nested virtualization, where nested KVM guests may need to >> >> run with a specific processor compatibility level. >> >> >> <snip> >> > >> > I booted a KVM guest on LPAR with this patch in the following scenarios: >> <snip> >> >> > 3. P11 guest on P11 host booted in P10 compat mode: No error observed >> This should have resulted in an error since booting a P11 guest on P10 >> compat mode host is not allowed with/without this patch. Can you please >> check your test env and share the boot results. > > - lscpu output (host P11 LPAR booted in p10 compat mode) > # lscpu > > 03:35:13 [3/3] > Architecture: ppc64le > Byte Order: Little Endian > CPU(s): 960 > On-line CPU(s) list: 0-959 > Model name: POWER10 (architected), altivec supported > Model: 2.0 (pvr 0082 0200) > Thread(s) per core: 8 > Core(s) per socket: 15 > Socket(s): 8 > Physical sockets: 4 > Physical chips: 2 > Physical cores/chip: 16 > > > - lscpu output from guest > # lscpu > Architecture: ppc64le > Byte Order: Little Endian > CPU(s): 4 > On-line CPU(s) list: 0-3 > Model name: Power11 (raw), altivec supported > Model: 2.0 (pvr 0082 0200) > Thread(s) per core: 1 > Core(s) per socket: 4 > Socket(s): 1 > Argh, this doesnt look right. The kernel patch should have prevented the P11 compat guest boot on P10 compat host. Looks like you havent used the corrosponding Qemu patch [1] that could have prevented this from happening.
Had a off mailing list discussion with Amit on how to address this issue and he will be sending a new version of the patch to address this issue. [1] https://lore.kernel.org/all/[email protected]/ > > > - QEMU command line > /usr/bin/qemu-system-ppc64 -device virtio-blk-pci,drive=drive0,id=virtblk0 \ > -drive file=/home/gautam/images/fc41.qcow2,format=qcow2,if=none,id=drive0 > \ > -m 100G -smp 4 -cpu host -nographic -machine pseries,ic-mode=xics -accel > kvm > > > Thanks, > Gautam > -- Cheers ~ Vaibhav
