Commit d0e5a8f2 authored by Bharata B Rao's avatar Bharata B Rao Committed by David Gibson
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spapr: Ensure all LMBs are represented in ibm,dynamic-memory 



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.

To work around this guest kernel bug, ensure that ibm,dynamic-memory
has information about all the LMBs (RMA, boot-time LMBs, future
hotpluggable LMBs, and dummy LMBs to cover the gap between RAM and
hotpluggable region).

RMA is represented separately by memory@0 node. Hence mark RMA LMBs
and also the LMBs for the gap b/n RAM and hotpluggable region as
reserved and as having no valid DRC so that these LMBs are not considered
by the guest.

Signed-off-by: default avatarBharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: default avatarMichael Roth <mdroth@linux.vnet.ibm.com>
Reviewed-by: default avatarNathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
parent bc9ca595

hw/ppc/spapr.c

+37 −20
Original line number Diff line number Diff line
@@ -762,14 +762,17 @@ 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 hotplug_lmb_start = spapr->hotplug_memory.base / lmb_size;

    uint32_t nr_lmbs = (spapr->hotplug_memory.base +

                       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;



    /*

     * Don't create the node if there are no DR LMBs.

     * Don't create the node if there is no hotpluggable memory

     */

    if (!nr_lmbs) {

    if (machine->ram_size == machine->maxram_size) {

        return 0;

    }
@@ -803,13 +806,14 @@ static int spapr_populate_drconf_memory(sPAPRMachineState *spapr, void *fdt) 
    int_buf[0] = cpu_to_be32(nr_lmbs);

    cur_index++;

    for (i = 0; i < nr_lmbs; i++) {

        uint64_t addr = i * lmb_size;

        uint32_t *dynamic_memory = cur_index;



        if (i >= hotplug_lmb_start) {

            sPAPRDRConnector *drc;

            sPAPRDRConnectorClass *drck;

        uint64_t addr = i * lmb_size + spapr->hotplug_memory.base;;

        uint32_t *dynamic_memory = cur_index;



        drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_LMB,

                                       addr/lmb_size);

            drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_LMB, i);

            g_assert(drc);

            drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
@@ -818,12 +822,25 @@ static int spapr_populate_drconf_memory(sPAPRMachineState *spapr, void *fdt) 
            dynamic_memory[2] = cpu_to_be32(drck->get_index(drc));

            dynamic_memory[3] = cpu_to_be32(0); /* reserved */

            dynamic_memory[4] = cpu_to_be32(numa_get_node(addr, NULL));

        if (addr < machine->ram_size ||

                    memory_region_present(get_system_memory(), addr)) {

            if (memory_region_present(get_system_memory(), addr)) {

                dynamic_memory[5] = cpu_to_be32(SPAPR_LMB_FLAGS_ASSIGNED);

            } else {

                dynamic_memory[5] = cpu_to_be32(0);

            }

        } else {

            /*

             * LMB information for RMA, boot time RAM and gap b/n RAM and

             * hotplug memory region -- all these are marked as reserved

             * and as having no valid DRC.

             */

            dynamic_memory[0] = cpu_to_be32(addr >> 32);

            dynamic_memory[1] = cpu_to_be32(addr & 0xffffffff);

            dynamic_memory[2] = cpu_to_be32(0);

            dynamic_memory[3] = cpu_to_be32(0); /* reserved */

            dynamic_memory[4] = cpu_to_be32(-1);

            dynamic_memory[5] = cpu_to_be32(SPAPR_LMB_FLAGS_RESERVED |

                                            SPAPR_LMB_FLAGS_DRC_INVALID);

        }



        cur_index += SPAPR_DR_LMB_LIST_ENTRY_SIZE;

    }

include/hw/ppc/spapr.h

+4 −2
Original line number Diff line number Diff line
@@ -620,9 +620,11 @@ 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_DRC_INVALID 0x00000020

#define SPAPR_LMB_FLAGS_RESERVED 0x00000080



#endif /* !defined (__HW_SPAPR_H__) */