spapr/xive: Fix migration of hot-plugged CPUs

The migration sequence of a guest using the XIVE exploitation mode
relies on the fact that the states of all devices are restored before
the machine is. This is not true for hot-plug devices such as CPUs
which state come after the machine. This breaks migration because the
thread interrupt context registers are not correctly set.

Fix migration of hotplugged CPUs by restoring their context in the
'post_load' handler of the XiveTCTX model.

Fixes: 277dd3d7712a ("spapr/xive: add migration support for KVM")
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20190813064853.29310-1-clg@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c
index 3bf8e7a20e14bb11beacf2260a288b8ed32be1cb..8898615c69f544f64bc1ed34c15cd8e3f47bef1b 100644 (file)
--- a/hw/intc/spapr_xive_kvm.c
+++ b/hw/intc/spapr_xive_kvm.c
@@ -72,11 +72,17 @@ static void kvm_cpu_disable_all(void)
  * XIVE Thread Interrupt Management context (KVM)
  */
 
-static void kvmppc_xive_cpu_set_state(XiveTCTX *tctx, Error **errp)
+void kvmppc_xive_cpu_set_state(XiveTCTX *tctx, Error **errp)
 {
+    SpaprXive *xive = SPAPR_MACHINE(qdev_get_machine())->xive;
     uint64_t state[2];
     int ret;
 
+    /* The KVM XIVE device is not in use yet */
+    if (xive->fd == -1) {
+        return;
+    }
+
     /* word0 and word1 of the OS ring. */
     state[0] = *((uint64_t *) &tctx->regs[TM_QW1_OS]);
 
@@ -655,7 +661,16 @@ int kvmppc_xive_post_load(SpaprXive *xive, int version_id)
         }
     }
 
-    /* Restore the thread interrupt contexts */
+    /*
+     * Restore the thread interrupt contexts of initial CPUs.
+     *
+     * The context of hotplugged CPUs is restored later, by the
+     * 'post_load' handler of the XiveTCTX model because they are not
+     * available at the time the SpaprXive 'post_load' method is
+     * called. We can not restore the context of all CPUs in the
+     * 'post_load' handler of XiveTCTX because the machine is not
+     * necessarily connected to the KVM device at that time.
+     */
     CPU_FOREACH(cs) {
         PowerPCCPU *cpu = POWERPC_CPU(cs);
 

diff --git a/hw/intc/xive.c b/hw/intc/xive.c
index cf77bdb7d34aad8ca05402c66a1d57f45e7fe43a..da148e9f6fc97053b522b02eac4dce1363f4e4b0 100644 (file)
--- a/hw/intc/xive.c
+++ b/hw/intc/xive.c
@@ -615,12 +615,31 @@ static int vmstate_xive_tctx_pre_save(void *opaque)
     return 0;
 }
 
+static int vmstate_xive_tctx_post_load(void *opaque, int version_id)
+{
+    Error *local_err = NULL;
+
+    if (kvm_irqchip_in_kernel()) {
+        /*
+         * Required for hotplugged CPU, for which the state comes
+         * after all states of the machine.
+         */
+        kvmppc_xive_cpu_set_state(XIVE_TCTX(opaque), &local_err);
+        if (local_err) {
+            error_report_err(local_err);
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
 static const VMStateDescription vmstate_xive_tctx = {
     .name = TYPE_XIVE_TCTX,
     .version_id = 1,
     .minimum_version_id = 1,
     .pre_save = vmstate_xive_tctx_pre_save,
-    .post_load = NULL, /* handled by the sPAPRxive model */
+    .post_load = vmstate_xive_tctx_post_load,
     .fields = (VMStateField[]) {
         VMSTATE_BUFFER(regs, XiveTCTX),
         VMSTATE_END_OF_LIST()

diff --git a/include/hw/ppc/xive.h b/include/hw/ppc/xive.h
index 55c53c74177655a6036574a9be7c61b16a1713b2..736335174a4cafb07fdc95df83b3bd5e62018f25 100644 (file)
--- a/include/hw/ppc/xive.h
+++ b/include/hw/ppc/xive.h
@@ -438,5 +438,6 @@ void kvmppc_xive_source_set_irq(void *opaque, int srcno, int val);
 void kvmppc_xive_cpu_connect(XiveTCTX *tctx, Error **errp);
 void kvmppc_xive_cpu_synchronize_state(XiveTCTX *tctx, Error **errp);
 void kvmppc_xive_cpu_get_state(XiveTCTX *tctx, Error **errp);
+void kvmppc_xive_cpu_set_state(XiveTCTX *tctx, Error **errp);
 
 #endif /* PPC_XIVE_H */