[PATCH RFC V2 02/37] cpus-common: Add common CPU utility for possible vCPUs

[Salil Mehta]

Adds various utility functions which might be required to fetch or check the
state of the possible vCPUs. This also introduces concept of *disabled* vCPUs,
which are part of the *possible* vCPUs but are not part of the *present* vCPU.
This state shall be used during machine init time to check the presence of
vcpus.

Co-developed-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Co-developed-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
---
 cpus-common.c         | 31 +++++++++++++++++++++++++
 include/hw/core/cpu.h | 53 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+)

diff --git a/cpus-common.c b/cpus-common.c
index 45c745ecf6..24c04199a1 100644
--- a/cpus-common.c
+++ b/cpus-common.c
@@ -24,6 +24,7 @@
 #include "sysemu/cpus.h"
 #include "qemu/lockable.h"
 #include "trace/trace-root.h"
+#include "hw/boards.h"
 
 QemuMutex qemu_cpu_list_lock;
 static QemuCond exclusive_cond;
@@ -107,6 +108,36 @@ void cpu_list_remove(CPUState *cpu)
     cpu_list_generation_id++;
 }
 
+CPUState *qemu_get_possible_cpu(int index)
+{
+    MachineState *ms = MACHINE(qdev_get_machine());
+    const CPUArchIdList *possible_cpus = ms->possible_cpus;
+
+    assert((index >= 0) && (index < possible_cpus->len));
+
+    return CPU(possible_cpus->cpus[index].cpu);
+}
+
+bool qemu_present_cpu(CPUState *cpu)
+{
+    return cpu;
+}
+
+bool qemu_enabled_cpu(CPUState *cpu)
+{
+    return cpu && !cpu->disabled;
+}
+
+uint64_t qemu_get_cpu_archid(int cpu_index)
+{
+    MachineState *ms = MACHINE(qdev_get_machine());
+    const CPUArchIdList *possible_cpus = ms->possible_cpus;
+
+    assert((cpu_index >= 0) && (cpu_index < possible_cpus->len));
+
+    return possible_cpus->cpus[cpu_index].arch_id;
+}
+
 CPUState *qemu_get_cpu(int index)
 {
     CPUState *cpu;
diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
index fdcbe87352..e5af79950c 100644
--- a/include/hw/core/cpu.h
+++ b/include/hw/core/cpu.h
@@ -413,6 +413,17 @@ struct CPUState {
     SavedIOTLB saved_iotlb;
 #endif
 
+    /*
+     * Some architectures do not allow *presence* of vCPUs to be changed
+     * after guest has booted using information specified by VMM/firmware
+     * via ACPI MADT at the boot time. Thus to enable vCPU hotplug on these
+     * architectures possible vCPU can have CPUState object in 'disabled'
+     * state or can also not have CPUState object at all. This is possible
+     * when vCPU Hotplug is supported and vCPUs are 'yet-to-be-plugged' in
+     * the QOM or have been hot-unplugged.
+     * By default every CPUState is enabled as of now across all archs.
+     */
+    bool disabled;
     /* TODO Move common fields from CPUArchState here. */
     int cpu_index;
     int cluster_index;
@@ -770,6 +781,48 @@ static inline bool cpu_in_exclusive_context(const CPUState 
*cpu)
  */
 CPUState *qemu_get_cpu(int index);
 
+/**
+ * qemu_get_possible_cpu:
+ * @index: The CPUState@cpu_index value of the CPU to obtain.
+ *         Input index MUST be in range [0, Max Possible CPUs)
+ *
+ * If CPUState object exists,then it gets a CPU matching
+ * @index in the possible CPU array.
+ *
+ * Returns: The possible CPU or %NULL if CPU does not exist.
+ */
+CPUState *qemu_get_possible_cpu(int index);
+
+/**
+ * qemu_present_cpu:
+ * @cpu: The vCPU to check
+ *
+ * Checks if the vCPU is amongst the present possible vcpus.
+ *
+ * Returns: True if it is present possible vCPU else false
+ */
+bool qemu_present_cpu(CPUState *cpu);
+
+/**
+ * qemu_enabled_cpu:
+ * @cpu: The vCPU to check
+ *
+ * Checks if the vCPU is enabled.
+ *
+ * Returns: True if it is 'enabled' else false
+ */
+bool qemu_enabled_cpu(CPUState *cpu);
+
+/**
+ * qemu_get_cpu_archid:
+ * @cpu_index: possible vCPU for which arch-id needs to be retreived
+ *
+ * Fetches the vCPU arch-id from the present possible vCPUs.
+ *
+ * Returns: arch-id of the possible vCPU
+ */
+uint64_t qemu_get_cpu_archid(int cpu_index);
+
 /**
  * cpu_exists:
  * @id: Guest-exposed CPU ID to lookup.
-- 
2.34.1