On 22/08/2024 05:04, Aneesh Kumar K.V wrote:

Steven Price [off-list ref] writes:

....

quoted

+static int rec_exit_ripas_change(struct kvm_vcpu *vcpu)
+{
+	struct kvm *kvm = vcpu->kvm;
+	struct realm *realm = &kvm->arch.realm;
+	struct realm_rec *rec = &vcpu->arch.rec;
+	unsigned long base = rec->run->exit.ripas_base;
+	unsigned long top = rec->run->exit.ripas_top;
+	unsigned long ripas = rec->run->exit.ripas_value & 1;
+	unsigned long top_ipa;
+	int ret = -EINVAL;
+
+	if (realm_is_addr_protected(realm, base) &&
+	    realm_is_addr_protected(realm, top - 1)) {
+		kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_page_cache,
+					   kvm_mmu_cache_min_pages(vcpu->arch.hw_mmu));
+		write_lock(&kvm->mmu_lock);
+		ret = realm_set_ipa_state(vcpu, base, top, ripas, &top_ipa);
+		write_unlock(&kvm->mmu_lock);
+	}
+
+	WARN(ret && ret != -ENOMEM,
+	     "Unable to satisfy SET_IPAS for %#lx - %#lx, ripas: %#lx\n",
+	     base, top, ripas);
+
+	/* Exit to VMM to complete the change */
+	kvm_prepare_memory_fault_exit(vcpu, base, top_ipa - base, false, false,
+				      ripas == 1);
+
+	return 0;
+}
+

arch/arm64/kvm/rme-exit.c:100:6: warning: variable 'top_ipa' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
        if (realm_is_addr_protected(realm, base) &&
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/arm64/kvm/rme-exit.c:114:44: note: uninitialized use occurs here
        kvm_prepare_memory_fault_exit(vcpu, base, top_ipa - base, false, false,
                                                  ^~~~~~~

I'm not sure why I didn't notice this before, if the condition is false
then we're hitting the WARN (i.e. this shouldn't happen), but I should
fix that up to handle the situation better.

Steve