[Qemu-devel] [PATCH v13 6/6] migration: Include migration support for machine check handling

[Aravinda Prasad <aravinda@linux.vnet.ibm.com>]

This patch includes migration support for machine check
handling. Especially this patch blocks VM migration
requests until the machine check error handling is
complete as (i) these errors are specific to the source
hardware and is irrelevant on the target hardware,
(ii) these errors cause data corruption and should
be handled before migration.

Signed-off-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
---
 hw/ppc/spapr.c         |   44 ++++++++++++++++++++++++++++++++++++++++++++
 hw/ppc/spapr_events.c  |   14 ++++++++++++++
 hw/ppc/spapr_rtas.c    |    2 ++
 include/hw/ppc/spapr.h |    2 ++
 4 files changed, 62 insertions(+)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 1c0908e..f6262f0 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -46,6 +46,7 @@
 #include "migration/qemu-file-types.h"
 #include "migration/global_state.h"
 #include "migration/register.h"
+#include "migration/blocker.h"
 #include "mmu-hash64.h"
 #include "mmu-book3s-v3.h"
 #include "cpu-models.h"
@@ -1829,6 +1830,8 @@ static void spapr_machine_reset(MachineState *machine)
 
     /* Signal all vCPUs waiting on this condition */
     qemu_cond_broadcast(&spapr->mc_delivery_cond);
+
+    migrate_del_blocker(spapr->fwnmi_migration_blocker);
 }
 
 static void spapr_create_nvram(SpaprMachineState *spapr)
@@ -2119,6 +2122,42 @@ static const VMStateDescription vmstate_spapr_dtb = {
     },
 };
 
+static bool spapr_fwnmi_needed(void *opaque)
+{
+    SpaprMachineState *spapr = (SpaprMachineState *)opaque;
+
+    return spapr->guest_machine_check_addr != -1;
+}
+
+static int spapr_fwnmi_post_load(void *opaque, int version_id)
+{
+    SpaprMachineState *spapr = (SpaprMachineState *)opaque;
+
+    if (spapr_get_cap(spapr, SPAPR_CAP_FWNMI_MCE) == SPAPR_CAP_ON) {
+
+        if (kvmppc_has_cap_ppc_fwnmi()) {
+            return 0;
+        }
+
+        return kvmppc_set_fwnmi();
+    }
+
+    return 0;
+}
+
+static const VMStateDescription vmstate_spapr_machine_check = {
+    .name = "spapr_machine_check",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = spapr_fwnmi_needed,
+    .post_load = spapr_fwnmi_post_load,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT64(guest_machine_check_addr, SpaprMachineState),
+        VMSTATE_INT32(mc_status, SpaprMachineState),
+        VMSTATE_END_OF_LIST()
+    },
+};
+
 static const VMStateDescription vmstate_spapr = {
     .name = "spapr",
     .version_id = 3,
@@ -2152,6 +2191,7 @@ static const VMStateDescription vmstate_spapr = {
         &vmstate_spapr_dtb,
         &vmstate_spapr_cap_large_decr,
         &vmstate_spapr_cap_ccf_assist,
+        &vmstate_spapr_machine_check,
         NULL
     }
 };
@@ -2948,6 +2988,10 @@ static void spapr_machine_init(MachineState *machine)
             exit(1);
         }
 
+        /* Create the error string for live migration blocker */
+        error_setg(&spapr->fwnmi_migration_blocker,
+            "Live migration not supported during machine check handling");
+
         /* Register ibm,nmi-register and ibm,nmi-interlock RTAS calls */
         spapr_fwnmi_register();
     }
diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
index ecc3d68..83f0a22 100644
--- a/hw/ppc/spapr_events.c
+++ b/hw/ppc/spapr_events.c
@@ -43,6 +43,7 @@
 #include "qemu/main-loop.h"
 #include "hw/ppc/spapr_ovec.h"
 #include <libfdt.h>
+#include "migration/blocker.h"
 
 #define RTAS_LOG_VERSION_MASK                   0xff000000
 #define   RTAS_LOG_VERSION_6                    0x06000000
@@ -844,6 +845,8 @@ void spapr_mce_req_event(PowerPCCPU *cpu, bool recovered)
 {
     SpaprMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
     CPUState *cs = CPU(cpu);
+    int ret;
+    Error *local_err = NULL;
 
     if (spapr->guest_machine_check_addr == -1) {
         /*
@@ -857,6 +860,17 @@ void spapr_mce_req_event(PowerPCCPU *cpu, bool recovered)
         return;
     }
 
+    ret = migrate_add_blocker(spapr->fwnmi_migration_blocker, &local_err);
+    if (ret < 0) {
+        /*
+         * We don't want to abort and let the migration to continue. In a
+         * rare case, the machine check handler will run on the target
+         * hardware. Though this is not preferable, it is better than aborting
+         * the migration or killing the VM.
+         */
+        warn_report_err(local_err);
+    }
+
     while (spapr->mc_status != -1) {
         /*
          * Check whether the same CPU got machine check error
diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
index d892583..b682cc2 100644
--- a/hw/ppc/spapr_rtas.c
+++ b/hw/ppc/spapr_rtas.c
@@ -50,6 +50,7 @@
 #include "hw/ppc/fdt.h"
 #include "target/ppc/mmu-hash64.h"
 #include "target/ppc/mmu-book3s-v3.h"
+#include "migration/blocker.h"
 
 static void rtas_display_character(PowerPCCPU *cpu, SpaprMachineState *spapr,
                                    uint32_t token, uint32_t nargs,
@@ -438,6 +439,7 @@ static void rtas_ibm_nmi_interlock(PowerPCCPU *cpu,
          */
         spapr->mc_status = -1;
         qemu_cond_signal(&spapr->mc_delivery_cond);
+        migrate_del_blocker(spapr->fwnmi_migration_blocker);
         rtas_st(rets, 0, RTAS_OUT_SUCCESS);
     }
 }
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index dada821..ea7625e 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -217,6 +217,8 @@ struct SpaprMachineState {
 
     unsigned gpu_numa_id;
     SpaprTpmProxy *tpm_proxy;
+
+    Error *fwnmi_migration_blocker;
 };
 
 #define H_SUCCESS         0