KVM: riscv: selftests: Add guest helper to get vcpu id

Add guest_get_vcpuid() helper to simplify accessing to per-cpu
private data. The sscratch CSR was used to store the vcpu id.
Signed-off-by: Haibo Xu <haibo1.xu@intel.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

tools/testing/selftests/kvm/include/aarch64/processor.h

@@ -226,8 +226,4 @@ void smccc_smc(uint32_t function_id, uint64_t arg0, uint64_t arg1,
 	       uint64_t arg2, uint64_t arg3, uint64_t arg4, uint64_t arg5,
 	       uint64_t arg6, struct arm_smccc_res *res);
 
-
-
-uint32_t guest_get_vcpuid(void);
-
 #endif /* SELFTEST_KVM_PROCESSOR_H */

tools/testing/selftests/kvm/include/kvm_util_base.h

@@ -1081,4 +1081,6 @@ void kvm_selftest_arch_init(void);
 
 void kvm_arch_vm_post_create(struct kvm_vm *vm);
 
+uint32_t guest_get_vcpuid(void);
+
 #endif /* SELFTEST_KVM_UTIL_BASE_H */

tools/testing/selftests/kvm/lib/riscv/processor.c

@@ -316,6 +316,9 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
 	vcpu_set_reg(vcpu, RISCV_CORE_REG(regs.sp), stack_vaddr + stack_size);
 	vcpu_set_reg(vcpu, RISCV_CORE_REG(regs.pc), (unsigned long)guest_code);
 
+	/* Setup sscratch for guest_get_vcpuid() */
+	vcpu_set_reg(vcpu, RISCV_GENERAL_CSR_REG(sscratch), vcpu_id);
+
 	/* Setup default exception vector of guest */
 	vcpu_set_reg(vcpu, RISCV_GENERAL_CSR_REG(stvec), (unsigned long)guest_unexp_trap);
 
@@ -437,6 +440,11 @@ void vm_install_interrupt_handler(struct kvm_vm *vm, exception_handler_fn handle
 	handlers->exception_handlers[1][0] = handler;
 }
 
+uint32_t guest_get_vcpuid(void)
+{
+	return csr_read(CSR_SSCRATCH);
+}
+
 struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,
 			unsigned long arg1, unsigned long arg2,
 			unsigned long arg3, unsigned long arg4,