[PATCH v3 3/6] KVM: s390: Allow 4k granularity for memslots

Claudio Imbrenda
2026-04-02T15:01:49Z

Until now memslots on s390 needed to have 1M granularity and be 1M
aligned. Since the new gmap code can handle memslots with 4k
granularity and alignment, remove the restrictions.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
---
arch/s390/kvm/kvm-s390.c | 20 ++++++--------------
1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index bc7d6fa66eaf..be2a721e2574 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -5636,8 +5636,6 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
struct kvm_memory_slot *new,
enum kvm_mr_change change)
{
- gpa_t size;
-
if (kvm_is_ucontrol(kvm) && new->id < KVM_USER_MEM_SLOTS)
return -EINVAL;

@@ -5647,20 +5645,14 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,

if (change != KVM_MR_DELETE && change != KVM_MR_FLAGS_ONLY) {
/*
- * A few sanity checks. We can have memory slots which have to be
- * located/ended at a segment boundary (1MB). The memory in userland is
- * ok to be fragmented into various different vmas. It is okay to mmap()
- * and munmap() stuff in this slot after doing this call at any time
+ * A few sanity checks. The memory in userland is ok to be
+ * fragmented into various different vmas. It is okay to mmap()
+ * and munmap() stuff in this slot after doing this call at any
+ * time.
*/
-
- if (new->userspace_addr & 0xffffful)
+ if (new->userspace_addr & ~PAGE_MASK)
return -EINVAL;
-
- size = new->npages * PAGE_SIZE;
- if (size & 0xffffful)
- return -EINVAL;
-
- if ((new->base_gfn * PAGE_SIZE) + size > kvm->arch.mem_limit)
+ if ((new->base_gfn + new->npages) * PAGE_SIZE > kvm->arch.mem_limit)
return -EINVAL;
}

--
2.53.0