KVM: selftests: Add 'malloc' failure check in vcpu_save_state

There is a 'malloc' call in vcpu_save_state function, which can
be unsuccessful. This patch will add the malloc failure checking
to avoid possible null dereference and give more information
about test fail reasons.
Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Link: https://lore.kernel.org/r/20230322144528.704077-1-ivan.orlov0322@gmail.comSigned-off-by: Sean Christopherson <seanjc@google.com>

tools/testing/selftests/kvm/lib/x86_64/processor.c

@@ -970,6 +970,7 @@ struct kvm_x86_state *vcpu_save_state(struct kvm_vcpu *vcpu)
 	vcpu_run_complete_io(vcpu);
 
 	state = malloc(sizeof(*state) + msr_list->nmsrs * sizeof(state->msrs.entries[0]));
+	TEST_ASSERT(state, "-ENOMEM when allocating kvm state");
 
 	vcpu_events_get(vcpu, &state->events);
 	vcpu_mp_state_get(vcpu, &state->mp_state);