[resending as I noticed that I dropped the ccs when I sent this last week]
On 07.12.2017 15:58, Christian Borntraeger wrote:
> 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>
> ---
This should not harm migration I guess. And it's easier than the other
alternatives we discussed.
> 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 )
KVM_SLOT_MAX_BYTES ?
(4096 -> TARGET_PAGE_SIZE, 0xfffff -> ? )
> +
> 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;
you can initialize these directly
> + 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;
> + }
chunk = MIN() ...
> + 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);
you could directly use number++ here, when initializing number to 1.
(then also the strange indentation of number++ above is gone )
> + }
> + g_free(name);
>
> /* Initialize storage key device */
> s390_skeys_init();
>
--
Thanks,
David / dhildenb
