Introduce CPUState.prefer_arch_id_over_cpu_index and
MachineClass.prefer_arch_id_over_cpu_index that allow target
machines to optionally switch to using arch_id instead of cpu_index
as instance_id in vmstate_register(). This will help allow successful
migration in cases where holes are introduced in cpu_index range
after CPU hot removals.
Whether to use arch_id or cpu_index is based on machine type version
and hence added MachineClass.prefer_arch_id_over_cpu_index. However the
enforcement is via and during CPU creation and hence added
CPUState.prefer_arch_id_over_cpu_index. So it becomes a two step
process for the target to enable the use of arch_id:
1. Set MachineClass.prefer_arch_id_over_cpu_index.
2. Ensure CPUState.prefer_arch_id_over_cpu_index is set for all CPUs
based on 1. above.
Suggested-by: Igor Mammedov <imamm...@redhat.com>
Signed-off-by: Bharata B Rao <bhar...@linux.vnet.ibm.com>
---
exec.c | 10 ++++++++--
include/hw/boards.h | 1 +
include/qom/cpu.h | 4 ++++
3 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/exec.c b/exec.c
index 8ce8e90..7cc1d06 100644
--- a/exec.c
+++ b/exec.c
@@ -616,15 +616,21 @@ static void cpu_release_index(CPUState *cpu)
bitmap_clear(cpu_index_map, cpu->cpu_index, 1);
}
+/*
+ * TODO: cpu_index and instance_id are of type int while .get_arch_id()is
+ * of type int64_t. What is the consequence of changing instance_id to int64_t
?
+ */
static void cpu_vmstate_register(CPUState *cpu)
{
CPUClass *cc = CPU_GET_CLASS(cpu);
+ int instance_id = cpu->prefer_arch_id_over_cpu_index ?
+ cc->get_arch_id(cpu) : cpu->cpu_index;
if (qdev_get_vmsd(DEVICE(cpu)) == NULL) {
- vmstate_register(NULL, cpu->cpu_index, &vmstate_cpu_common, cpu);
+ vmstate_register(NULL, instance_id, &vmstate_cpu_common, cpu);
}
if (cc->vmsd != NULL) {
- vmstate_register(NULL, cpu->cpu_index, cc->vmsd, cpu);
+ vmstate_register(NULL, instance_id, cc->vmsd, cpu);
}
}
diff --git a/include/hw/boards.h b/include/hw/boards.h
index 3ed6155..decabba 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -123,6 +123,7 @@ struct MachineClass {
ram_addr_t default_ram_size;
bool option_rom_has_mr;
bool rom_file_has_mr;
+ bool prefer_arch_id_over_cpu_index;
HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
DeviceState *dev);
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index 32f3af3..1f1706e 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -273,6 +273,9 @@ struct qemu_work_item {
* @kvm_fd: vCPU file descriptor for KVM.
* @work_mutex: Lock to prevent multiple access to queued_work_*.
* @queued_work_first: First asynchronous work pending.
+ * @prefer_arch_id_over_cpu_index: Set to enforce the use of
+ * CPUClass.get_arch_id() over cpu_index during vmstate registration
+ * and any other uses by target machine where arch_id is preferred.
*
* State of one CPU core or thread.
*/
@@ -360,6 +363,7 @@ struct CPUState {
(absolute value) offset as small as possible. This reduces code
size, especially for hosts without large memory offsets. */
uint32_t tcg_exit_req;
+ bool prefer_arch_id_over_cpu_index;
};
QTAILQ_HEAD(CPUTailQ, CPUState);
--
2.7.4
