On 13/06/2017 22:18, Laurent Vivier wrote:
> On 12/06/2017 16:37, David Gibson wrote:
>> On Thu, Jun 08, 2017 at 07:27:42PM +0200, Laurent Vivier wrote:
>>> If the OS is not started, QEMU sends an event to the OS
>>> that is lost and cannot be recovered. An unplug is not
>>> able to restore QEMU in a coherent state.
>>> So, while the OS is not started, disable CPU and memory hotplug.
>>> We guess the OS is started if the CAS has been negotiated.
>>>
>>> Signed-off-by: Laurent Vivier <lviv...@redhat.com>
>>
>> It seems a pain to introduce a whole new (migrated) variable just to
>> check this. Could we instead tweak the allocation of spapr->ov5_cas,
>> so it is NULL until CAS is completed?
>
> I think it's a good idea to use ov5_cas, but we need to modify some
> functions to manage the NULL pointer (spapr_ovec_test(),
> spapr_ovec_populate_dt()), and I have some issues to manage the NULL
> pointer in migration:
>
> - with the previous releases, if it is NULL, we don't want to migrate it
> because previous releases are not able to manage a NULL pointer, so we
> don't migrate it (spapr_ov5_cas_needed() should be false if ov5_cas is
> NULL) letting it to its default value (initialized but empty) in this
> case on the destination,
>
> - with the current version, if it is not NULL, we to want migrate it,
> but the destination guest crashes because the pointer on the destination
> is NULL and there is no memory the receive the data.
>
> I think the problem is we can't migrate ov5_cas if it is not initialized
> on the destination side[0]. Perhaps I've missed something but it seems a
> NULL pointer can't be migrated and thus cannot be used as a state marker.
>
> Any idea?
>
> Thanks,
> Laurent
>
> [0] Perhaps we could use a VMSTATE_XXX() with a VMS_ALLOC flag instead
> of VMSTATE_STRUCT_POINTER_V() to allocate the memory on the destination?
>
This is what I've tried but migration crashes if the OS is started on
source guest (ov5_cas != NULL, because on destination guest ov5_cas ==
NULL and the guest doesn't allocate the memory on migration). I think my
v2 looks cleaner.
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index b2951d7..742cbe7 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1343,7 +1343,7 @@ static void ppc_spapr_reset(void)
* negotiated options and start from scratch */
if (!spapr->cas_reboot) {
spapr_ovec_cleanup(spapr->ov5_cas);
- spapr->ov5_cas = spapr_ovec_new();
+ spapr->ov5_cas = NULL;
}
fdt = spapr_build_fdt(spapr, rtas_addr, spapr->rtas_size);
@@ -1457,6 +1457,10 @@ static bool spapr_ov5_cas_needed(void *opaque)
sPAPROptionVector *ov5_removed = spapr_ovec_new();
bool cas_needed;
+ if (spapr->ov5_cas == NULL) {
+ return false;
+ }
+
/* Prior to the introduction of sPAPROptionVector, we had two option
* vectors we dealt with: OV5_FORM1_AFFINITY, and OV5_DRCONF_MEMORY.
* Both of these options encode machine topology into the device-tree
@@ -2105,7 +2109,7 @@ static void ppc_spapr_init(MachineState *machine)
/* Set up containers for ibm,client-set-architecture negotiated
options */
spapr->ov5 = spapr_ovec_new();
- spapr->ov5_cas = spapr_ovec_new();
+ spapr->ov5_cas = NULL;
if (smc->dr_lmb_enabled) {
spapr_ovec_set(spapr->ov5, OV5_DRCONF_MEMORY);
@@ -2604,6 +2608,7 @@ out:
static void spapr_memory_pre_plug(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);
@@ -2616,6 +2621,15 @@ static void spapr_memory_pre_plug(HotplugHandler
*hotplug_dev, DeviceState *dev,
return;
}
+ if (dev->hotplugged) {
+ if (!runstate_check(RUN_STATE_PRELAUNCH) &&
+ !runstate_check(RUN_STATE_INMIGRATE) &&
+ ms->ov5_cas == NULL) {
+ error_setg(errp, "Memory hotplug not supported without OS");
+ return;
+ }
+ }
+
mem_dev = object_property_get_str(OBJECT(dimm),
PC_DIMM_MEMDEV_PROP, NULL);
if (mem_dev && !kvmppc_is_mem_backend_page_size_ok(mem_dev)) {
error_setg(errp, "Memory backend has bad page size. "
@@ -2919,6 +2933,7 @@ static void spapr_core_pre_plug(HotplugHandler
*hotplug_dev, DeviceState *dev,
Error **errp)
{
MachineState *machine = MACHINE(OBJECT(hotplug_dev));
+ sPAPRMachineState *ms = SPAPR_MACHINE(machine);
MachineClass *mc = MACHINE_GET_CLASS(hotplug_dev);
Error *local_err = NULL;
CPUCore *cc = CPU_CORE(dev);
@@ -2927,9 +2942,18 @@ static void spapr_core_pre_plug(HotplugHandler
*hotplug_dev, DeviceState *dev,
CPUArchId *core_slot;
int index;
- if (dev->hotplugged && !mc->has_hotpluggable_cpus) {
- error_setg(&local_err, "CPU hotplug not supported for this
machine");
- goto out;
+ if (dev->hotplugged) {
+ if (!mc->has_hotpluggable_cpus) {
+ error_setg(&local_err,
+ "CPU hotplug not supported for this machine");
+ goto out;
+ }
+ if (!runstate_check(RUN_STATE_PRELAUNCH) &&
+ !runstate_check(RUN_STATE_INMIGRATE) &&
+ ms->ov5_cas == NULL) {
+ error_setg(&local_err, "CPU hotplug not supported without OS");
+ goto out;
+ }
}
if (strcmp(base_core_type, type)) {
diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
index aa1ffea..fa25a34 100644
--- a/hw/ppc/spapr_hcall.c
+++ b/hw/ppc/spapr_hcall.c
@@ -1133,6 +1133,10 @@ static target_ulong
h_client_architecture_support(PowerPCCPU *cpu,
guest_radix = spapr_ovec_test(ov5_guest, OV5_MMU_RADIX_300);
spapr_ovec_clear(ov5_guest, OV5_MMU_RADIX_300);
+ if (spapr->ov5_cas == NULL) {
+ spapr->ov5_cas = spapr_ovec_new();
+ }
+
/* NOTE: there are actually a number of ov5 bits where input from the
* guest is always zero, and the platform/QEMU enables them
independently
* of guest input. To model these properly we'd want some sort of mask,
diff --git a/hw/ppc/spapr_ovec.c b/hw/ppc/spapr_ovec.c
index 41df4c3..5f0c2d9 100644
--- a/hw/ppc/spapr_ovec.c
+++ b/hw/ppc/spapr_ovec.c
@@ -128,9 +128,12 @@ void spapr_ovec_clear(sPAPROptionVector *ov, long
bitnr)
bool spapr_ovec_test(sPAPROptionVector *ov, long bitnr)
{
- g_assert(ov);
g_assert_cmpint(bitnr, <, OV_MAXBITS);
+ if (ov == NULL) {
+ return false;
+ }
+
return test_bit(bitnr, ov->bitmap) ? true : false;
}
@@ -217,7 +220,10 @@ int spapr_ovec_populate_dt(void *fdt, int fdt_offset,
unsigned long lastbit;
int i;
- g_assert(ov);
+ if (ov == NULL) {
+ vec[0] = 0;
+ return fdt_setprop(fdt, fdt_offset, name, vec, 2);
+ }
