KVM: selftests: Only muck with SREGS on x86 in mmu_stress_test

Try to get/set SREGS in mmu_stress_test only when running on x86, as the
ioctls are supported only by x86 and PPC, and the latter doesn't yet
support KVM selftests.

Reviewed-by: James Houghton <jthoughton@google.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20241128005547.4077116-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

tools/testing/selftests/kvm/mmu_stress_test.c

@@ -59,23 +59,23 @@ static void run_vcpu(struct kvm_vcpu *vcpu)
 
 static void *vcpu_worker(void *data)
 {
+	struct kvm_sregs __maybe_unused sregs;
 	struct vcpu_info *info = data;
 	struct kvm_vcpu *vcpu = info->vcpu;
 	struct kvm_vm *vm = vcpu->vm;
-	struct kvm_sregs sregs;
 
 	vcpu_args_set(vcpu, 3, info->start_gpa, info->end_gpa, vm->page_size);
 
 	rendezvous_with_boss();
 
 	run_vcpu(vcpu);
 	rendezvous_with_boss();
-	vcpu_sregs_get(vcpu, &sregs);
 #ifdef __x86_64__
+	vcpu_sregs_get(vcpu, &sregs);
 	/* Toggle CR0.WP to trigger a MMU context reset. */
 	sregs.cr0 ^= X86_CR0_WP;
-#endif
 	vcpu_sregs_set(vcpu, &sregs);
+#endif
 	rendezvous_with_boss();
 
 	run_vcpu(vcpu);