diff mbox series

[015/113] spapr: register dummy ICPs later

Message ID 20180619014319.28272-16-mdroth@linux.vnet.ibm.com
State New
Headers show
Series [001/113] block/ssh: fix possible segmentation fault when .desc is not null-terminated | expand

Commit Message

Michael Roth June 19, 2018, 1:41 a.m. UTC 
From: Greg Kurz <groug@kaod.org>

Some older machine types create more ICPs than needed. We hence
need to register up to xics_max_server_number() dummy ICPs to
accomodate the migration of these machine types.

Recent VSMT rework changed xics_max_server_number() to return

    DIV_ROUND_UP(max_cpus * spapr->vsmt, smp_threads)

instead of

    DIV_ROUND_UP(max_cpus * kvmppc_smt_threads(), smp_threads);

The change is okay but it requires spapr->vsmt to be set, which
isn't the case with the current code. This causes the formula to
return zero and we don't create dummy ICPs. This breaks migration
of older guests as reported here:

    https://bugzilla.redhat.com/show_bug.cgi?id=1549087

The dummy ICP workaround doesn't really have a dependency on XICS
itself. But it does depend on proper VCPU id numbering and it must
be applied before creating vCPUs (ie, creating real ICPs). So this
patch moves the workaround to spapr_init_cpus(), which already
assumes VSMT to be set.

Fixes: 72194664c8a1 ("spapr: use spapr->vsmt to compute VCPU ids")
Reported-by: Lukas Doktor <ldoktor@redhat.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
(cherry picked from commit 72fdd4de8e5fdc1a6078e000835fb54592a3fe97)
Signed-off-by: Greg Kurz <groug@kaod.org>
---
 hw/ppc/spapr.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)
diff mbox series

Patch

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index d53123c127..1a2dd1f597 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -184,7 +184,6 @@  static int xics_max_server_number(sPAPRMachineState *spapr)
 static void xics_system_init(MachineState *machine, int nr_irqs, Error **errp)
 {
     sPAPRMachineState *spapr = SPAPR_MACHINE(machine);
-    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(machine);
 
     if (kvm_enabled()) {
         if (machine_kernel_irqchip_allowed(machine) &&
@@ -206,17 +205,6 @@  static void xics_system_init(MachineState *machine, int nr_irqs, Error **errp)
             return;
         }
     }
-
-    if (smc->pre_2_10_has_unused_icps) {
-        int i;
-
-        for (i = 0; i < xics_max_server_number(spapr); i++) {
-            /* Dummy entries get deregistered when real ICPState objects
-             * are registered during CPU core hotplug.
-             */
-            pre_2_10_vmstate_register_dummy_icp(i);
-        }
-    }
 }
 
 static int spapr_fixup_cpu_smt_dt(void *fdt, int offset, PowerPCCPU *cpu,
@@ -2210,6 +2198,7 @@  static void spapr_init_cpus(sPAPRMachineState *spapr)
 {
     MachineState *machine = MACHINE(spapr);
     MachineClass *mc = MACHINE_GET_CLASS(machine);
+    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(machine);
     const char *type = spapr_get_cpu_core_type(machine->cpu_type);
     const CPUArchIdList *possible_cpus;
     int boot_cores_nr = smp_cpus / smp_threads;
@@ -2240,6 +2229,17 @@  static void spapr_init_cpus(sPAPRMachineState *spapr)
         boot_cores_nr = possible_cpus->len;
     }
 
+    if (smc->pre_2_10_has_unused_icps) {
+        int i;
+
+        for (i = 0; i < xics_max_server_number(spapr); i++) {
+            /* Dummy entries get deregistered when real ICPState objects
+             * are registered during CPU core hotplug.
+             */
+            pre_2_10_vmstate_register_dummy_icp(i);
+        }
+    }
+
     for (i = 0; i < possible_cpus->len; i++) {
         int core_id = i * smp_threads;