KVM: PPC: Book3S: Introduce new hcall H_COPY_TOFROM_GUEST to access quadrants 1 & 2

A guest cannot access quadrants 1 or 2 as this would result in an
exception. Thus introduce the hcall H_COPY_TOFROM_GUEST to be used by a
guest when it wants to perform an access to quadrants 1 or 2, for
example when it wants to access memory for one of its nested guests.

Also provide an implementation for the kvm-hv module.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

arch/powerpc/kvm/book3s_64_mmu_radix.c

@@ -29,9 +29,9 @@
  */
 static int p9_supported_radix_bits[4] = { 5, 9, 9, 13 };
 
-static unsigned long __kvmhv_copy_tofrom_guest_radix(int lpid, int pid,
-					gva_t eaddr, void *to, void *from,
-					unsigned long n)
+unsigned long __kvmhv_copy_tofrom_guest_radix(int lpid, int pid,
+					      gva_t eaddr, void *to, void *from,
+					      unsigned long n)
 {
 	unsigned long quadrant, ret = n;
 	int old_pid, old_lpid;
@@ -82,6 +82,7 @@ static unsigned long __kvmhv_copy_tofrom_guest_radix(int lpid, int pid,
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(__kvmhv_copy_tofrom_guest_radix);
 
 static long kvmhv_copy_tofrom_guest_radix(struct kvm_vcpu *vcpu, gva_t eaddr,
 					  void *to, void *from, unsigned long n)

arch/powerpc/kvm/book3s_hv.c

@@ -996,7 +996,11 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
 		if (nesting_enabled(vcpu->kvm))
 			ret = kvmhv_do_nested_tlbie(vcpu);
 		break;
-
+	case H_COPY_TOFROM_GUEST:
+		ret = H_FUNCTION;
+		if (nesting_enabled(vcpu->kvm))
+			ret = kvmhv_copy_tofrom_guest_nested(vcpu);
+		break;
 	default:
 		return RESUME_HOST;
 	}

arch/powerpc/kvm/book3s_hv_nested.c

@@ -461,6 +461,81 @@ long kvmhv_set_partition_table(struct kvm_vcpu *vcpu)
 	return ret;
 }
 
+/*
+ * Handle the H_COPY_TOFROM_GUEST hcall.
+ * r4 = L1 lpid of nested guest
+ * r5 = pid
+ * r6 = eaddr to access
+ * r7 = to buffer (L1 gpa)
+ * r8 = from buffer (L1 gpa)
+ * r9 = n bytes to copy
+ */
+long kvmhv_copy_tofrom_guest_nested(struct kvm_vcpu *vcpu)
+{
+	struct kvm_nested_guest *gp;
+	int l1_lpid = kvmppc_get_gpr(vcpu, 4);
+	int pid = kvmppc_get_gpr(vcpu, 5);
+	gva_t eaddr = kvmppc_get_gpr(vcpu, 6);
+	gpa_t gp_to = (gpa_t) kvmppc_get_gpr(vcpu, 7);
+	gpa_t gp_from = (gpa_t) kvmppc_get_gpr(vcpu, 8);
+	void *buf;
+	unsigned long n = kvmppc_get_gpr(vcpu, 9);
+	bool is_load = !!gp_to;
+	long rc;
+
+	if (gp_to && gp_from) /* One must be NULL to determine the direction */
+		return H_PARAMETER;
+
+	if (eaddr & (0xFFFUL << 52))
+		return H_PARAMETER;
+
+	buf = kzalloc(n, GFP_KERNEL);
+	if (!buf)
+		return H_NO_MEM;
+
+	gp = kvmhv_get_nested(vcpu->kvm, l1_lpid, false);
+	if (!gp) {
+		rc = H_PARAMETER;
+		goto out_free;
+	}
+
+	mutex_lock(&gp->tlb_lock);
+
+	if (is_load) {
+		/* Load from the nested guest into our buffer */
+		rc = __kvmhv_copy_tofrom_guest_radix(gp->shadow_lpid, pid,
+						     eaddr, buf, NULL, n);
+		if (rc)
+			goto not_found;
+
+		/* Write what was loaded into our buffer back to the L1 guest */
+		rc = kvm_vcpu_write_guest(vcpu, gp_to, buf, n);
+		if (rc)
+			goto not_found;
+	} else {
+		/* Load the data to be stored from the L1 guest into our buf */
+		rc = kvm_vcpu_read_guest(vcpu, gp_from, buf, n);
+		if (rc)
+			goto not_found;
+
+		/* Store from our buffer into the nested guest */
+		rc = __kvmhv_copy_tofrom_guest_radix(gp->shadow_lpid, pid,
+						     eaddr, NULL, buf, n);
+		if (rc)
+			goto not_found;
+	}
+
+out_unlock:
+	mutex_unlock(&gp->tlb_lock);
+	kvmhv_put_nested(gp);
+out_free:
+	kfree(buf);
+	return rc;
+not_found:
+	rc = H_NOT_FOUND;
+	goto out_unlock;
+}
+
 /*
  * Reload the partition table entry for a guest.
  * Caller must hold gp->tlb_lock.