KVM does not allow memory regions > KVM_MEM_MAX_NR_PAGES, basically limiting the memory per slot to 7.999TB. Lets split the base memory into 4TB chunks to allow go beyond 8TB for a guest. With that (and optimistic overcommitment in the kernel) I was able to start a 59TB guest on a 1TB system.
Signed-off-by: Christian Borntraeger <[email protected]> --- hw/s390x/s390-virtio-ccw.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c index 8425534..6735bbb 100644 --- a/hw/s390x/s390-virtio-ccw.c +++ b/hw/s390x/s390-virtio-ccw.c @@ -157,11 +157,25 @@ static void virtio_ccw_register_hcalls(void) static void s390_memory_init(ram_addr_t mem_size) { MemoryRegion *sysmem = get_system_memory(); - MemoryRegion *ram = g_new(MemoryRegion, 1); + ram_addr_t chunk, offset; + gchar *name; /* allocate RAM for core */ - memory_region_allocate_system_memory(ram, NULL, "s390.ram", mem_size); - memory_region_add_subregion(sysmem, 0, ram); + offset = 0; + while (mem_size) { + MemoryRegion *ram = g_new(MemoryRegion, 1); + chunk = mem_size; + /* KVM does not allow memslots >= 8 TB. Lets split into 4TB chunks */ + if (chunk > 4UL * 1024 * 1024 * 1024 * 1024) { + chunk = 4UL * 1024 * 1024 * 1024 * 1024; + } + name = g_strdup_printf("s390.ram[0x%lx]", offset); + memory_region_allocate_system_memory(ram, NULL, name, chunk); + memory_region_add_subregion(sysmem, offset, ram); + mem_size -= chunk; + offset += chunk; + g_free(name); + } /* Initialize storage key device */ s390_skeys_init(); -- 2.9.4
