On Fri, Jun 03, 2016 at 11:19:44AM +0530, Bharata B Rao wrote: > Memory hotplug can fail for some combinations of RAM and maxmem when > DDW is enabled in the presence of devices like nec-usb-xhci. DDW depends > on maximum addressable memory returned by guest and this value is currently > being calculated wrongly by the guest kernel routine memory_hotplug_max(). > While there is an attempt to fix the guest kernel, this patch works > around the problem within QEMU itself. > > memory_hotplug_max() routine in the guest kernel arrives at max > addressable memory by multiplying lmb-size with the lmb-count obtained > from ibm,dynamic-memory property. There are two assumptions here: > > - All LMBs are part of ibm,dynamic memory: This is not true for PowerKVM > where only hot-pluggable LMBs are present in this property. > - The memory area comprising of RAM and hotplug region is contiguous: This > needn't be true always for PowerKVM as there can be gap between > boot time RAM and hotplug region. > > This work around involves having all the LMBs (RMA, rest of the boot time > LMBs and hot-pluggable LMBs) as part of ibm,dynamic-memory so that > guest kernel's calculation of max addressable memory comes out correct > resulting in correct DDW value which prevents memory hotplug failures. > memory@0 is created for RMA, but RMA LMBs are also represented as > "reserved" LMBs in ibm,dynamic-memory. Parts of this are essenitally a > revert of e8f986fc57a664a74b9f685b466506366a15201b. > > In addition to this, the alignment of hotplug memory region is reduced from > current 1G to 256M (LMB size in PowerKVM) so that we don't end up with any > gaps between boot time RAM and hotplug region.
Hmm.. could we work around the problem without altering the memory
alignment by inserting extra dummy reserved LMBs covering the gap?
>
> Signed-off-by: Bharata B Rao <bhar...@linux.vnet.ibm.com>
> ---
> hw/ppc/spapr.c | 59
> +++++++++++++++++++++++++++++++++++---------------
> include/hw/ppc/spapr.h | 5 +++--
> 2 files changed, 45 insertions(+), 19 deletions(-)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 623c35f..3dfbc37 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -569,7 +569,6 @@ static int spapr_populate_memory(sPAPRMachineState
> *spapr, void *fdt)
> }
> if (!mem_start) {
> /* ppc_spapr_init() checks for rma_size <= node0_size already */
> - spapr_populate_memory_node(fdt, i, 0, spapr->rma_size);
> mem_start += spapr->rma_size;
> node_size -= spapr->rma_size;
> }
> @@ -762,18 +761,13 @@ 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_rma_lmbs = spapr->rma_size / lmb_size;
> + uint32_t nr_lmbs = machine->maxram_size / lmb_size;
> + uint32_t nr_assigned_lmbs = machine->ram_size / lmb_size;
> uint32_t *int_buf, *cur_index, buf_len;
> int nr_nodes = nb_numa_nodes ? nb_numa_nodes : 1;
>
> /*
> - * Don't create the node if there are no DR LMBs.
> - */
> - if (!nr_lmbs) {
> - return 0;
> - }
> -
> - /*
> * Allocate enough buffer size to fit in ibm,dynamic-memory
> * or ibm,associativity-lookup-arrays
> */
> @@ -805,9 +799,15 @@ static int
> spapr_populate_drconf_memory(sPAPRMachineState *spapr, void *fdt)
> for (i = 0; i < nr_lmbs; i++) {
> sPAPRDRConnector *drc;
> sPAPRDRConnectorClass *drck;
> - uint64_t addr = i * lmb_size + spapr->hotplug_memory.base;;
> + uint64_t addr;
> uint32_t *dynamic_memory = cur_index;
>
> + if (i < nr_assigned_lmbs) {
> + addr = i * lmb_size;
> + } else {
> + addr = (i - nr_assigned_lmbs) * lmb_size +
> + spapr->hotplug_memory.base;
> + }
> drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_LMB,
> addr/lmb_size);
> g_assert(drc);
> @@ -820,7 +820,11 @@ static int
> spapr_populate_drconf_memory(sPAPRMachineState *spapr, void *fdt)
> dynamic_memory[4] = cpu_to_be32(numa_get_node(addr, NULL));
> if (addr < machine->ram_size ||
> memory_region_present(get_system_memory(), addr)) {
> - dynamic_memory[5] = cpu_to_be32(SPAPR_LMB_FLAGS_ASSIGNED);
> + if (i < nr_rma_lmbs) {
> + dynamic_memory[5] = cpu_to_be32(SPAPR_LMB_FLAGS_RESERVED);
> + } else {
> + dynamic_memory[5] = cpu_to_be32(SPAPR_LMB_FLAGS_ASSIGNED);
> + }
> } else {
> dynamic_memory[5] = cpu_to_be32(0);
> }
> @@ -882,6 +886,8 @@ int spapr_h_cas_compose_response(sPAPRMachineState *spapr,
> /* Generate ibm,dynamic-reconfiguration-memory node if required */
> if (memory_update && smc->dr_lmb_enabled) {
> _FDT((spapr_populate_drconf_memory(spapr, fdt)));
> + } else {
> + _FDT((spapr_populate_memory(spapr, fdt)));
> }
>
> /* Pack resulting tree */
> @@ -919,10 +925,23 @@ static void spapr_finalize_fdt(sPAPRMachineState *spapr,
> /* open out the base tree into a temp buffer for the final tweaks */
> _FDT((fdt_open_into(spapr->fdt_skel, fdt, FDT_MAX_SIZE)));
>
> - ret = spapr_populate_memory(spapr, fdt);
> - if (ret < 0) {
> - fprintf(stderr, "couldn't setup memory nodes in fdt\n");
> - exit(1);
> + /*
> + * Add memory@0 node to represent RMA. Rest of the memory is either
> + * represented by memory nodes or ibm,dynamic-reconfiguration-memory
> + * node later during ibm,client-architecture-support call.
> + *
> + * If NUMA is configured, ensure that memory@0 ends up in the
> + * first memory-less node.
> + */
> + if (nb_numa_nodes) {
> + for (i = 0; i < nb_numa_nodes; ++i) {
> + if (numa_info[i].node_mem) {
> + spapr_populate_memory_node(fdt, i, 0, spapr->rma_size);
> + break;
> + }
> + }
> + } else {
> + spapr_populate_memory_node(fdt, 0, 0, spapr->rma_size);
> }
>
> ret = spapr_populate_vdevice(spapr->vio_bus, fdt);
> @@ -1654,14 +1673,20 @@ 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 = machine->maxram_size / lmb_size;
> + uint32_t nr_assigned_lmbs = machine->ram_size / lmb_size;
> int i;
>
> for (i = 0; i < nr_lmbs; i++) {
> sPAPRDRConnector *drc;
> uint64_t addr;
>
> - addr = i * lmb_size + spapr->hotplug_memory.base;
> + if (i < nr_assigned_lmbs) {
> + addr = i * lmb_size;
> + } else {
> + addr = (i - nr_assigned_lmbs) * lmb_size +
> + spapr->hotplug_memory.base;
> + }
> drc = spapr_dr_connector_new(OBJECT(spapr),
> SPAPR_DR_CONNECTOR_TYPE_LMB,
> addr/lmb_size);
> qemu_register_reset(spapr_drc_reset, drc);
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index b2aeb15..e5ef979 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -619,9 +619,10 @@ int spapr_rng_populate_dt(void *fdt);
> #define SPAPR_DR_LMB_LIST_ENTRY_SIZE 6
>
> /*
> - * This flag value defines the LMB as assigned in ibm,dynamic-memory
> - * property under ibm,dynamic-reconfiguration-memory node.
> + * Defines for flag value in ibm,dynamic-memory property under
> + * ibm,dynamic-reconfiguration-memory node.
> */
> #define SPAPR_LMB_FLAGS_ASSIGNED 0x00000008
> +#define SPAPR_LMB_FLAGS_RESERVED 0x00000080
>
> #endif /* !defined (__HW_SPAPR_H__) */
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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