KVM: selftests: Add arch specific initialization

Introduce arch specific API: kvm_selftest_arch_init to allow each arch to
handle initialization before running any selftest logic.

Suggested-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Andrew Jones <andrew.jones@linux.dev>
Reviewed-by: Peter Gonda <pgonda@google.com>
Signed-off-by: Vishal Annapurve <vannapurve@google.com>
Link: https://lore.kernel.org/r/20221115213845.3348210-3-vannapurve@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

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

@@ -857,4 +857,11 @@ static inline int __vm_disable_nx_huge_pages(struct kvm_vm *vm)
 	return __vm_enable_cap(vm, KVM_CAP_VM_DISABLE_NX_HUGE_PAGES, 0);
 }
 
+/*
+ * Arch hook that is invoked via a constructor, i.e. before exeucting main(),
+ * to allow for arch-specific setup that is common to all tests, e.g. computing
+ * the default guest "mode".
+ */
+void kvm_selftest_arch_init(void);
+
 #endif /* SELFTEST_KVM_UTIL_BASE_H */

tools/testing/selftests/kvm/lib/aarch64/processor.c

@@ -495,15 +495,6 @@ void aarch64_get_supported_page_sizes(uint32_t ipa,
 	close(kvm_fd);
 }
 
-/*
- * arm64 doesn't have a true default mode, so start by computing the
- * available IPA space and page sizes early.
- */
-void __attribute__((constructor)) init_guest_modes(void)
-{
-       guest_modes_append_default();
-}
-
 void smccc_hvc(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)
@@ -528,3 +519,12 @@ void smccc_hvc(uint32_t function_id, uint64_t arg0, uint64_t arg1,
 		       [arg4] "r"(arg4), [arg5] "r"(arg5), [arg6] "r"(arg6)
 		     : "x0", "x1", "x2", "x3", "x4", "x5", "x6", "x7");
 }
+
+void kvm_selftest_arch_init(void)
+{
+	/*
+	 * arm64 doesn't have a true default mode, so start by computing the
+	 * available IPA space and page sizes early.
+	 */
+	guest_modes_append_default();
+}

tools/testing/selftests/kvm/lib/kvm_util.c

@@ -2087,8 +2087,14 @@ void __vm_get_stat(struct kvm_vm *vm, const char *stat_name, uint64_t *data,
 	}
 }
 
+__weak void kvm_selftest_arch_init(void)
+{
+}
+
 void __attribute((constructor)) kvm_selftest_init(void)
 {
 	/* Tell stdout not to buffer its content. */
 	setbuf(stdout, NULL);
+
+	kvm_selftest_arch_init();
 }