Re: [PATCH v4 09/18] KVM: arm64: selftests: Add guest support to get the vcpuid

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h

b/tools/testing/selftests/kvm/include/kvm_util.h
index 010b59b13917..0e87cb0c980b 100644

--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h

@@ -400,4 +400,24 @@ uint64_t get_ucall(struct kvm_vm *vm, uint32_t

vcpu_id, struct ucall *uc);
 int vm_get_stats_fd(struct kvm_vm *vm);
 int vcpu_get_stats_fd(struct kvm_vm *vm, uint32_t vcpuid);

+#define VM_CPUID_MAP_INVAL -1
+
+struct vm_cpuid_map {
+       uint64_t hw_cpuid;
+       int vcpuid;
+};
+
+/*
+ * Create a vcpuid:hw_cpuid map and export it to the guest
+ *
+ * Input Args:
+ *   vm - KVM VM.
+ *
+ * Output Args: None
+ *
+ * Must be called after all the vCPUs are added to the VM
+ */
+void vm_cpuid_map_init(struct kvm_vm *vm);
+int guest_get_vcpuid(void);
+
 #endif /* SELFTEST_KVM_UTIL_H */

diff --git a/tools/testing/selftests/kvm/lib/aarch64/processor.c

b/tools/testing/selftests/kvm/lib/aarch64/processor.c
index db64ee206064..e796bb3984a6 100644

--- a/tools/testing/selftests/kvm/lib/aarch64/processor.c
+++ b/tools/testing/selftests/kvm/lib/aarch64/processor.c

@@ -16,6 +16,8 @@

 static vm_vaddr_t exception_handlers;

+static struct vm_cpuid_map cpuid_map[KVM_MAX_VCPUS];
+
 static uint64_t page_align(struct kvm_vm *vm, uint64_t v)
 {
        return (v + vm->page_size) & ~(vm->page_size - 1);

@@ -426,3 +428,42 @@ void vm_install_exception_handler(struct kvm_vm

*vm, int vector,
        assert(vector < VECTOR_NUM);
        handlers->exception_handlers[vector][0] = handler;
 }
+
+void vm_cpuid_map_init(struct kvm_vm *vm)
+{
+       int i = 0;
+       struct vcpu *vcpu;
+       struct vm_cpuid_map *map;
+
+       TEST_ASSERT(!list_empty(&vm->vcpus), "vCPUs must have been created\n");
+
+       list_for_each_entry(vcpu, &vm->vcpus, list) {
+               map = &cpuid_map[i++];
+               map->vcpuid = vcpu->id;
+               get_reg(vm, vcpu->id,
KVM_ARM64_SYS_REG(SYS_MPIDR_EL1), &map->hw_cpuid);
+               map->hw_cpuid &= MPIDR_HWID_BITMASK;
+       }
+
+       if (i < KVM_MAX_VCPUS)
+               cpuid_map[i].vcpuid = VM_CPUID_MAP_INVAL;
+
+       sync_global_to_guest(vm, cpuid_map);
+}
+
+int guest_get_vcpuid(void)
+{
+       int i, vcpuid;
+       uint64_t mpidr = read_sysreg(mpidr_el1) & MPIDR_HWID_BITMASK;
+
+       for (i = 0; i < KVM_MAX_VCPUS; i++) {
+               vcpuid = cpuid_map[i].vcpuid;
+
+               /* Was this vCPU added to the VM after the map was
initialized? */
+               GUEST_ASSERT_1(vcpuid != VM_CPUID_MAP_INVAL, mpidr);
+
+               if (mpidr == cpuid_map[i].hw_cpuid)
+                       return vcpuid;
+       }
+
+       /* We should not be reaching here */
+       GUEST_ASSERT_1(0, mpidr);
+       return -1;
+}

This would ensure that we don't have a sparse array and can use the
last non-vCPU element as a sentinal node.
If you still feel preparing the map as and when the vCPUs are created
makes more sense, I can go for it.