On Mon, Oct 26, 2015 at 03:23:05PM +0530, Bharata B Rao wrote: > Add support to hot remove pc-dimm memory devices.
Sorry it's taken me so long to look at this.
> TODO: In response to memory hot removal operation on a DIMM device,
> guest kernel might refuse to offline a few LMBs that are part of that device.
> In such cases, we will have a DIMM device that has some LMBs online and some
> LMBs offline. To avoid this situation, drmgr could be enhanced to support
> a command line option that results in removal of all the LMBs or none.
Hm.. what would be the end result of such a situation? We want to
handle it as gracefully as we can, even if the guest has old tools.
Is there some way we can detect this failure condition, and re-connect
the DIMM?
It does highlight the fact that the PAPR hotplug interface and the
pc-dimm model don't work together terribly well. I think we have to
try to support it for the sake of management layers, but I do wonder
if we ought to thinkg about an alternative "lmb-pool" backend, where
the precise location of memory blocks isn't so important. With some
thought such a backend might also be useful for paravirt x86.
Which also makes me think, I wonder if it would be possible to wire up
a PAPR compatible interface to qemu's balloon backend, since in some
ways the PAPR memory hotplug model acts more like a balloon (in that
the guest physical address of removed LMBs isn't usually important to
the host).
Still, we need to get the dimm backed model working first, I guess.
Apart from those overall considerations, the patch looks good.
> Signed-off-by: Bharata B Rao <bhar...@linux.vnet.ibm.com>
> ---
> Changes in v1:
> - Got rid of the patch that introduced a field in PCDIMMDevice to track
> DIMM marked for removal since we can track that using within DRC
> object.
> - Removed the patch that added return value to rtas_set_indicator()
> since the required changes are already pushed by Michael Roth.
>
> v0:
>
> hw/ppc/spapr.c | 90
> +++++++++++++++++++++++++++++++++++++++++++++++++++++-
> hw/ppc/spapr_drc.c | 18 +++++++++++
> 2 files changed, 107 insertions(+), 1 deletion(-)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index e1202ce..f5b1ac2 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2174,6 +2174,85 @@ out:
> error_propagate(errp, local_err);
> }
>
> +typedef struct sPAPRDIMMState {
> + uint32_t nr_lmbs;
> +} sPAPRDIMMState;
> +
> +static void spapr_lmb_release(DeviceState *dev, void *opaque)
> +{
> + sPAPRDIMMState *ds = (sPAPRDIMMState *)opaque;
> + HotplugHandler *hotplug_ctrl = NULL;
> + Error *local_err = NULL;
> +
> + if (--ds->nr_lmbs) {
> + return;
> + }
> +
> + g_free(ds);
> +
> + /*
> + * Now that all the LMBs have been removed by the guest, call the
> + * pc-dimm unplug handler to cleanup up the pc-dimm device.
> + */
> + hotplug_ctrl = qdev_get_hotplug_handler(dev);
> + hotplug_handler_unplug(hotplug_ctrl, dev, &local_err);
> +}
> +
> +static void spapr_del_lmbs(DeviceState *dev, uint64_t addr, uint64_t size,
> + Error **errp)
> +{
> + sPAPRDRConnector *drc;
> + sPAPRDRConnectorClass *drck;
> + uint32_t nr_lmbs = size/SPAPR_MEMORY_BLOCK_SIZE;
> + Error *local_err = NULL;
> + int i;
> + sPAPRDIMMState *ds = g_malloc0(sizeof(sPAPRDIMMState));
> +
> + ds->nr_lmbs = nr_lmbs;
> + for (i = 0; i < nr_lmbs; i++) {
> + drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_LMB,
> + addr/SPAPR_MEMORY_BLOCK_SIZE);
> + g_assert(drc);
> +
> + drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> + drck->detach(drc, dev, spapr_lmb_release, ds, &local_err);
> + addr += SPAPR_MEMORY_BLOCK_SIZE;
> + }
> + spapr_hotplug_req_remove_by_count(SPAPR_DR_CONNECTOR_TYPE_LMB, nr_lmbs);
> +}
> +
> +static void spapr_memory_unplug(HotplugHandler *hotplug_dev, DeviceState
> *dev,
> + Error **errp)
> +{
> + sPAPRMachineState *ms = SPAPR_MACHINE(hotplug_dev);
> + PCDIMMDevice *dimm = PC_DIMM(dev);
> + PCDIMMDeviceClass *ddc = PC_DIMM_GET_CLASS(dimm);
> + MemoryRegion *mr = ddc->get_memory_region(dimm);
> +
> + pc_dimm_memory_unplug(dev, &ms->hotplug_memory, mr);
> + object_unparent(OBJECT(dev));
> +}
> +
> +static void spapr_memory_unplug_request(HotplugHandler *hotplug_dev,
> + DeviceState *dev, Error **errp)
> +{
> + Error *local_err = NULL;
> + PCDIMMDevice *dimm = PC_DIMM(dev);
> + PCDIMMDeviceClass *ddc = PC_DIMM_GET_CLASS(dimm);
> + MemoryRegion *mr = ddc->get_memory_region(dimm);
> + uint64_t size = memory_region_size(mr);
> + uint64_t addr;
> +
> + addr = object_property_get_int(OBJECT(dimm), PC_DIMM_ADDR_PROP,
> &local_err);
> + if (local_err) {
> + goto out;
> + }
> +
> + spapr_del_lmbs(dev, addr, size, &local_err);
> +out:
> + error_propagate(errp, local_err);
> +}
> +
> static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
> DeviceState *dev, Error **errp)
> {
> @@ -2221,7 +2300,15 @@ static void spapr_machine_device_unplug(HotplugHandler
> *hotplug_dev,
> DeviceState *dev, Error **errp)
> {
> if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> - error_setg(errp, "Memory hot unplug not supported by sPAPR");
> + spapr_memory_unplug(hotplug_dev, dev, errp);
> + }
> +}
> +
> +static void spapr_machine_device_unplug_request(HotplugHandler *hotplug_dev,
> + DeviceState *dev, Error
> **errp)
> +{
> + if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> + spapr_memory_unplug_request(hotplug_dev, dev, errp);
> }
> }
>
> @@ -2263,6 +2350,7 @@ static void spapr_machine_class_init(ObjectClass *oc,
> void *data)
> hc->plug = spapr_machine_device_plug;
> hc->unplug = spapr_machine_device_unplug;
> mc->cpu_index_to_socket_id = spapr_cpu_index_to_socket_id;
> + hc->unplug_request = spapr_machine_device_unplug_request;
>
> smc->dr_lmb_enabled = false;
> fwc->get_dev_path = spapr_get_fw_dev_path;
> diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c
> index 5d6ea7c..59b6ea9 100644
> --- a/hw/ppc/spapr_drc.c
> +++ b/hw/ppc/spapr_drc.c
> @@ -11,6 +11,7 @@
> */
>
> #include "hw/ppc/spapr_drc.h"
> +#include "hw/ppc/spapr.h"
> #include "qom/object.h"
> #include "hw/qdev.h"
> #include "qapi/visitor.h"
> @@ -77,6 +78,23 @@ static uint32_t set_isolation_state(sPAPRDRConnector *drc,
> }
> }
>
> + /*
> + * Fail any request to ISOLATE the LMB DRC if this LMB doesn't
> + * belong to a DIMM device that is marked for removal.
> + *
> + * Currently the guest userspace tool drmgr that drives the memory
> + * hotplug/unplug will just try to remove a set of 'removable' LMBs
> + * in response to a hot unplug request that is based on drc-count.
> + * If the LMB being removed doesn't belong to a DIMM device that is
> + * actually being unplugged, fail the isolation request here.
> + */
> + if (drc->type == SPAPR_DR_CONNECTOR_TYPE_LMB) {
> + if ((state == SPAPR_DR_ISOLATION_STATE_ISOLATED) &&
> + !drc->awaiting_release) {
> + return RTAS_OUT_HW_ERROR;
> + }
> + }
> +
> drc->isolation_state = state;
>
> if (drc->isolation_state == SPAPR_DR_ISOLATION_STATE_ISOLATED) {
--
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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