KVM does not allow memory regions > KVM_MEM_MAX_NR_PAGES, basically
limiting the memory per slot to 8TB-4k. Lets start a new memory region
if we cross that boundary.
With that (and optimistic overcommitment in the kernel) I was able to
start a 24TB guest on a 1TB system.
Signed-off-by: Christian Borntraeger <borntrae...@de.ibm.com>
---
hw/s390x/s390-virtio-ccw.c | 33 ++++++++++++++++++++++++++++++---
1 file changed, 30 insertions(+), 3 deletions(-)
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 8425534..3630f6a 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -154,14 +154,41 @@ static void virtio_ccw_register_hcalls(void)
virtio_ccw_hcall_early_printk);
}
+/*
+ * KVM does only support memory slots up to KVM_MEM_MAX_NR_PAGES pages
+ * as the dirty bitmap must be managed by bitops that take an int as
+ * position indicator. If we have a guest beyond that we will split off
+ * new subregions.
+ */
+#define KVM_SLOT_MAX ((((1UL << 31) - 1) * 4096) & ~0xfffffUL )
+
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;
+ unsigned int number;
+ 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;
+ number = 0;
+ name = g_strdup_printf("s390.ram");
+ while (mem_size) {
+ MemoryRegion *ram = g_new(MemoryRegion, 1);
+ chunk = mem_size;
+ /* KVM does not allow memslots >= 8 TB */
+ if (chunk > KVM_SLOT_MAX) {
+ chunk = KVM_SLOT_MAX;
+ }
+ memory_region_allocate_system_memory(ram, NULL, name, chunk);
+ memory_region_add_subregion(sysmem, offset, ram);
+ mem_size -= chunk;
+ offset += chunk;
+ number++;
+ g_free(name);
+ name = g_strdup_printf("s390.ram.%u", number);
+ }
+ g_free(name);
/* Initialize storage key device */
s390_skeys_init();
--
2.9.4
