Re: [Qemu-devel] [RFC v1 1/2] spapr: Accommadate alignment gaps in hotplug memory region

[Igor Mammedov]

On Fri,  9 Oct 2015 12:19:59 +0530
Bharata B Rao <address@hidden> wrote:

> Accommodate enough space in hotplug memory region so that it will
> be possible to align memory in each slot to 256M. When PowerPC memory
> hotplug enables inter-dimm gaps, then we could end up having
> unused/unassigned 256M memory chuck between DIMMs in the hotplug
s/chuck/chunks/

> memory region. Hence create DRC objects spanning the entire
> alignment-adjusted hotplug memory region instead of just the acutal
> hotpluggable size (machine->maxram_size - machine->ram_size).
> 
> In addition, pass 256M alignment to pc_dimm_memory_plug() so that
> the DIMM address gets aligned to 256M.
> 
> Signed-off-by: Bharata B Rao <address@hidden>
beside fixup above,
Reviewed-by: Igor Mammedov <address@hidden>

> ---
>  hw/ppc/spapr.c | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index fc5e7d6..4a901f0 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -721,7 +721,7 @@ static int
> spapr_populate_drconf_memory(sPAPRMachineState *spapr, void *fdt) int
> ret, i, offset; uint64_t lmb_size = SPAPR_MEMORY_BLOCK_SIZE;
>      uint32_t prop_lmb_size[] = {0, cpu_to_be32(lmb_size)};
> -    uint32_t nr_lmbs = (machine->maxram_size -
> machine->ram_size)/lmb_size;
> +    uint32_t nr_lmbs =
> memory_region_size(&spapr->hotplug_memory.mr)/lmb_size; uint32_t
> *int_buf, *cur_index, buf_len; int nr_nodes = nb_numa_nodes ?
> nb_numa_nodes : 1; 
> @@ -1614,9 +1614,8 @@ static void spapr_drc_reset(void *opaque)
>  
>  static void spapr_create_lmb_dr_connectors(sPAPRMachineState *spapr)
>  {
> -    MachineState *machine = MACHINE(spapr);
>      uint64_t lmb_size = SPAPR_MEMORY_BLOCK_SIZE;
> -    uint32_t nr_lmbs = (machine->maxram_size -
> machine->ram_size)/lmb_size;
> +    uint32_t nr_lmbs =
> memory_region_size(&spapr->hotplug_memory.mr)/lmb_size; int i;
>  
>      for (i = 0; i < nr_lmbs; i++) {
> @@ -1792,6 +1791,20 @@ static void ppc_spapr_init(MachineState
> *machine) 
>          spapr->hotplug_memory.base = ROUND_UP(machine->ram_size,
>                                                SPAPR_HOTPLUG_MEM_ALIGN);
> +
> +        /*
> +         * Ensure that there is enough space in the hotplug memory
> +         * region to support a maximum alignment of 256M per slot.
> +         * Though PowerPC has 16M and 16G huge pages, PowerKVM
> supports
> +         * only 16M and hence 256M alignment works until we start
> +         * supporting 1G hugepage.
> +         *
> +         * Instead of max hugepage size alignment, we go with 256M
> +         * alignment because we require the DIMM address to be 256M
> +         * aligned as we maintain DRC objects for every 256M memory
> +         * chunk in the hotplug memory region.
> +         */
> +        hotplug_mem_size +=  SPAPR_MEMORY_BLOCK_SIZE *
> machine->ram_slots; memory_region_init(&spapr->hotplug_memory.mr,
> OBJECT(spapr), "hotplug-memory", hotplug_mem_size);
>          memory_region_add_subregion(sysmem,
> spapr->hotplug_memory.base, @@ -2114,7 +2127,7 @@ static void
> spapr_memory_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> PCDIMMDevice *dimm = PC_DIMM(dev); PCDIMMDeviceClass *ddc =
> PC_DIMM_GET_CLASS(dimm); MemoryRegion *mr =
> ddc->get_memory_region(dimm);
> -    uint64_t align = memory_region_get_alignment(mr);
> +    uint64_t align = SPAPR_MEMORY_BLOCK_SIZE;
>      uint64_t size = memory_region_size(mr);
>      uint64_t addr;
>