On 06.12.2017 13:00, Christian Borntraeger wrote: > 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(); >
This will most certainly break migration, no? 1. I remember the name being used for migration, I might be wrong. 2. Migration of guests > 4TB is certainly broken ;) I wonder if this should rather be handled in the kvm_slot code. (silently create an manage two slots) -- Thanks, David / dhildenb
