KVM is not happy when starting a VM with weird RAM sizes:
# qemu-system-s390x --enable-kvm --nographic -m 1234K
qemu-system-s390x: kvm_set_user_memory_region: KVM_SET_USER_MEMORY_REGION
failed, slot=0, start=0x0, size=0x244000: Invalid argument
kvm_set_phys_mem: error registering slot: Invalid argument
Aborted (core dumped)
Let's handle that in a better way by rejecting such weird RAM sizes
right from the start:
# qemu-system-s390x --enable-kvm --nographic -m 1234K
qemu-system-s390x: ram size must be multiples of 1 MiB
Message-ID: <20241219144115.2820241-2-da...@redhat.com>
Acked-by: Michael S. Tsirkin <m...@redhat.com>
Reviewed-by: Eric Farman <far...@linux.ibm.com>
Reviewed-by: Thomas Huth <th...@redhat.com>
Acked-by: Janosch Frank <fran...@linux.ibm.com>
Signed-off-by: David Hildenbrand <da...@redhat.com>
---
hw/s390x/s390-virtio-ccw.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 67ae34aead..f2a17ecace 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -180,6 +180,17 @@ static void s390_memory_init(MemoryRegion *ram)
{
MemoryRegion *sysmem = get_system_memory();
+ if (!QEMU_IS_ALIGNED(memory_region_size(ram), 1 * MiB)) {
+ /*
+ * SCLP cannot possibly expose smaller granularity right now and KVM
+ * cannot handle smaller granularity. As we don't support NUMA, the
+ * region size directly corresponds to machine->ram_size, and the
region
+ * is a single RAM memory region.
+ */
+ error_report("ram size must be multiples of 1 MiB");
+ exit(EXIT_FAILURE);
+ }
+
/* allocate RAM for core */
memory_region_add_subregion(sysmem, 0, ram);
--
2.47.1
