[PATCH v2 0/5] KVM: s390: Enable 4k granularity for memslots

From: Claudio Imbrenda

Date: Wed Apr 01 2026 - 13:43:41 EST


Currently the memslot granularity for s390 VMs is 1M. Both the s390
core architecture and virtio-mem only support a 1M granularity for
guest memory.

Notwithstanding the official architectural limits, it can be beneficial
to support memslots with 4k granularity. With the new gmap code, this
is a quite simple change. This allows us to enable more existing
selftests and makes KVM on s390 more future proof.


(Please note that v1 of this series was not sent publicly)

v1->v2
* Fixed the first patch (thanks Christian)


Claudio Imbrenda (5):
KVM: s390: Add some useful mask macros
KVM: s390: Add alignment checks for hugepages
KVM: s390: Allow 4k granularity for memslots
KVM: selftests: Remove 1M alignment requirement for s390
KVM: s390: selftests: enable some common memory-related tests

arch/s390/kvm/dat.h | 5 +++
arch/s390/kvm/faultin.c | 2 +-
arch/s390/kvm/gaccess.c | 2 +-
arch/s390/kvm/gmap.c | 32 +++++++++++++++----
arch/s390/kvm/gmap.h | 3 +-
arch/s390/kvm/kvm-s390.c | 20 ++++--------
tools/testing/selftests/kvm/Makefile.kvm | 11 ++-----
.../testing/selftests/kvm/include/kvm_util.h | 4 ---
tools/testing/selftests/kvm/lib/kvm_util.c | 9 +-----
9 files changed, 45 insertions(+), 43 deletions(-)

--
2.53.0