[Qemu-devel] [PATCH v2] spapr: manage hotplugged devices while the VM is not started

[Laurent Vivier <lvivier@redhat.com>]

For QEMU, a hotlugged device is a device added using the HMP/QMP
interface.
For SPAPR, a hotplugged device is a device added while the
machine is running. In this case QEMU doesn't update internal
state but relies on the OS for this part

In the case of migration, when we (libvirt) hotplug a device
on the source guest, we (libvirt) generally hotplug the same
device on the destination guest. But in this case, the machine
is stopped (RUN_STATE_INMIGRATE) and QEMU must not expect
the OS will manage it as an hotplugged device as it will
be "imported" by the migration.

This patch changes the meaning of "hotplugged" in spapr.c
to manage a QEMU hotplugged device like a "coldplugged" one
when the machine is awaiting an incoming migration.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
---
v2: fix the minor nit reported by dgibson

    I repost the patch as I think it is good to have
    devices in a good state before migration (it is
    generally a pre-requisite for migration), 
    so a hotplugged CPU before incoming migration
    appears like a coldplugged one, and moreover
    it fixes the use case in which CPU are hotplugged
    on both side (src and dest), and we try to unplug
    the CPU after the migration.

 hw/ppc/spapr.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 91b4057..d5a3587 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2518,6 +2518,12 @@ static void spapr_nmi(NMIState *n, int cpu_index, Error **errp)
     }
 }
 
+static bool spapr_coldplugged(DeviceState *dev)
+{
+    return runstate_check(RUN_STATE_INMIGRATE) ||
+           !dev->hotplugged;
+}
+
 static void spapr_add_lmbs(DeviceState *dev, uint64_t addr_start, uint64_t size,
                            uint32_t node, bool dedicated_hp_event_source,
                            Error **errp)
@@ -2528,6 +2534,7 @@ static void spapr_add_lmbs(DeviceState *dev, uint64_t addr_start, uint64_t size,
     int i, fdt_offset, fdt_size;
     void *fdt;
     uint64_t addr = addr_start;
+    bool coldplugged = spapr_coldplugged(dev);
 
     for (i = 0; i < nr_lmbs; i++) {
         drc = spapr_drc_by_id(TYPE_SPAPR_DRC_LMB,
@@ -2539,9 +2546,9 @@ static void spapr_add_lmbs(DeviceState *dev, uint64_t addr_start, uint64_t size,
                                                 SPAPR_MEMORY_BLOCK_SIZE);
 
         drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
-        drck->attach(drc, dev, fdt, fdt_offset, !dev->hotplugged, errp);
+        drck->attach(drc, dev, fdt, fdt_offset, coldplugged, errp);
         addr += SPAPR_MEMORY_BLOCK_SIZE;
-        if (!dev->hotplugged) {
+        if (coldplugged) {
             /* guests expect coldplugged LMBs to be pre-allocated */
             drck->set_allocation_state(drc, SPAPR_DR_ALLOCATION_STATE_USABLE);
             drck->set_isolation_state(drc, SPAPR_DR_ISOLATION_STATE_UNISOLATED);
@@ -2550,7 +2557,7 @@ static void spapr_add_lmbs(DeviceState *dev, uint64_t addr_start, uint64_t size,
     /* send hotplug notification to the
      * guest only in case of hotplugged memory
      */
-    if (dev->hotplugged) {
+    if (!coldplugged) {
         if (dedicated_hp_event_source) {
             drc = spapr_drc_by_id(TYPE_SPAPR_DRC_LMB,
                                   addr_start / SPAPR_MEMORY_BLOCK_SIZE);
@@ -2863,6 +2870,7 @@ static void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
     int smt = kvmppc_smt_threads();
     CPUArchId *core_slot;
     int index;
+    bool coldplugged = spapr_coldplugged(dev);
 
     core_slot = spapr_find_cpu_slot(MACHINE(hotplug_dev), cc->core_id, &index);
     if (!core_slot) {
@@ -2884,7 +2892,7 @@ static void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
 
     if (drc) {
         sPAPRDRConnectorClass *drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
-        drck->attach(drc, dev, fdt, fdt_offset, !dev->hotplugged, &local_err);
+        drck->attach(drc, dev, fdt, fdt_offset, coldplugged, &local_err);
         if (local_err) {
             g_free(fdt);
             error_propagate(errp, local_err);
@@ -2892,7 +2900,7 @@ static void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
         }
     }
 
-    if (dev->hotplugged) {
+    if (!coldplugged) {
         /*
          * Send hotplug notification interrupt to the guest only in case
          * of hotplugged CPUs.
-- 
2.9.4