Re: [PATCH] target/s390x: Make container ids in SysIB_15x 1-based

[Cornelia Huck <cohuck@redhat.com>]

On Tue, May 12 2026, Christian Borntraeger <borntraeger@linux.ibm.com> wrote:

> Am 11.05.26 um 15:49 schrieb Alexandra Winter:
>> The Container Id in a container-type TLE of SysIB_15x is defined as 8-bit
>> unsigned nonzero integer. Make stsi fc 15 emulation architecture compliant,
>> by starting the container ids at 1 for the lowest numbered container.
>> 
>> The qemu misbehaviour without this patch becomes obvious due to a recently
>> proposed kernel fix. Older linux kernels pass the container ids from stsi
>> fc15 unchanged to sysfs, i.e. starting at 1 on s390 hardware. This resulted
>> in off-by-one values when compared to the values from HMC. A Linux kernel
>> fix is being proposed to correct the sysfs topology ids by -1, so they
>> start at 0, e.g. when displayed by 'lscpu -ye'. In case a KVM guest with a
>> fixed kernel runs on a host with a qemu without this fix, this can result
>> in container ids erroneously being shown as 255.
>> Example (Fixed guest on unfixed qemu):
>> $ lscpu -ye
>> CPU NODE DRAWER BOOK SOCKET CORE L1d:L1i:L2 ONLINE CONFIGURED POLARIZATION ADDRESS
>>    0    0    255  255    255    0 0:0:0         yes yes        vert-medium  0
>>    1    0    255  255      0    1 1:1:1         yes yes        vert-medium  1
>> After this fix:
>> $ lscpu -ye
>> CPU NODE DRAWER BOOK SOCKET CORE L1d:L1i:L2 ONLINE CONFIGURED POLARIZATION ADDRESS
>>    0    0      0    0      0    0 0:0:0         yes yes        vert-medium  0
>>    1    0      0    0      1    1 1:1:1         yes yes        vert-medium  1
>> 
>> Fixes: f4f54b582f ("target/s390x/cpu topology: handle STSI(15) and build the SYSIB")
>> Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
>
> Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>
>
> I guess this should go via Connys s390 tree.

Yep, that makes sense.