KVM: s390: Storage key functions refactoring

Refactor some storage key functions to improve readability.

Introduce helper functions that will be used in the next patches.

Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

Author: Claudio Imbrenda

arch/s390/kvm/gaccess.c

@@ -961,7 +961,7 @@ int access_guest_real(struct kvm_vcpu *vcpu, unsigned long gra,
  *            *@old_addr contains the value at @gpa before the attempt to
  *            exchange the value.
  * @new: The value to place at @gpa.
- * @access_key: The access key to use for the guest access.
+ * @acc: The access key to use for the guest access.
  * @success: output value indicating if an exchange occurred.
  *
  * Atomically exchange the value at @gpa by @new, if it contains *@old.
@@ -974,9 +974,8 @@ int access_guest_real(struct kvm_vcpu *vcpu, unsigned long gra,
  *         * -EAGAIN: transient failure (len 1 or 2)
  *         * -EOPNOTSUPP: read-only memslot (should never occur)
  */
-int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len,
-			       __uint128_t *old_addr, __uint128_t new,
-			       u8 access_key, bool *success)
+int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len, union kvm_s390_quad *old_addr,
+			       union kvm_s390_quad new, u8 acc, bool *success)
 {
 	gfn_t gfn = gpa_to_gfn(gpa);
 	struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
@@ -1008,41 +1007,42 @@ int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len,
 	case 1: {
 		u8 old;
 
-		ret = cmpxchg_user_key((u8 __user *)hva, &old, *old_addr, new, access_key);
-		*success = !ret && old == *old_addr;
-		*old_addr = old;
+		ret = cmpxchg_user_key((u8 __user *)hva, &old, old_addr->one, new.one, acc);
+		*success = !ret && old == old_addr->one;
+		old_addr->one = old;
 		break;
 	}
 	case 2: {
 		u16 old;
 
-		ret = cmpxchg_user_key((u16 __user *)hva, &old, *old_addr, new, access_key);
-		*success = !ret && old == *old_addr;
-		*old_addr = old;
+		ret = cmpxchg_user_key((u16 __user *)hva, &old, old_addr->two, new.two, acc);
+		*success = !ret && old == old_addr->two;
+		old_addr->two = old;
 		break;
 	}
 	case 4: {
 		u32 old;
 
-		ret = cmpxchg_user_key((u32 __user *)hva, &old, *old_addr, new, access_key);
-		*success = !ret && old == *old_addr;
-		*old_addr = old;
+		ret = cmpxchg_user_key((u32 __user *)hva, &old, old_addr->four, new.four, acc);
+		*success = !ret && old == old_addr->four;
+		old_addr->four = old;
 		break;
 	}
 	case 8: {
 		u64 old;
 
-		ret = cmpxchg_user_key((u64 __user *)hva, &old, *old_addr, new, access_key);
-		*success = !ret && old == *old_addr;
-		*old_addr = old;
+		ret = cmpxchg_user_key((u64 __user *)hva, &old, old_addr->eight, new.eight, acc);
+		*success = !ret && old == old_addr->eight;
+		old_addr->eight = old;
 		break;
 	}
 	case 16: {
 		__uint128_t old;
 
-		ret = cmpxchg_user_key((__uint128_t __user *)hva, &old, *old_addr, new, access_key);
-		*success = !ret && old == *old_addr;
-		*old_addr = old;
+		ret = cmpxchg_user_key((__uint128_t __user *)hva, &old, old_addr->sixteen,
+				       new.sixteen, acc);
+		*success = !ret && old == old_addr->sixteen;
+		old_addr->sixteen = old;
 		break;
 	}
 	default:

arch/s390/kvm/gaccess.h

@@ -206,8 +206,8 @@ int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
 int access_guest_real(struct kvm_vcpu *vcpu, unsigned long gra,
 		      void *data, unsigned long len, enum gacc_mode mode);
 
-int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len, __uint128_t *old,
-			       __uint128_t new, u8 access_key, bool *success);
+int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len, union kvm_s390_quad *old_addr,
+			       union kvm_s390_quad new, u8 access_key, bool *success);
 
 /**
  * write_guest_with_key - copy data from kernel space to guest space

arch/s390/kvm/kvm-s390.c

@@ -2900,9 +2900,9 @@ static int mem_op_validate_common(struct kvm_s390_mem_op *mop, u64 supported_fla
 static int kvm_s390_vm_mem_op_abs(struct kvm *kvm, struct kvm_s390_mem_op *mop)
 {
 	void __user *uaddr = (void __user *)mop->buf;
+	void *tmpbuf __free(kvfree) = NULL;
 	enum gacc_mode acc_mode;
-	void *tmpbuf = NULL;
-	int r, srcu_idx;
+	int r;
 
 	r = mem_op_validate_common(mop, KVM_S390_MEMOP_F_SKEY_PROTECTION |
 					KVM_S390_MEMOP_F_CHECK_ONLY);
@@ -2915,52 +2915,36 @@ static int kvm_s390_vm_mem_op_abs(struct kvm *kvm, struct kvm_s390_mem_op *mop)
 			return -ENOMEM;
 	}
 
-	srcu_idx = srcu_read_lock(&kvm->srcu);
+	acc_mode = mop->op == KVM_S390_MEMOP_ABSOLUTE_READ ? GACC_FETCH : GACC_STORE;
 
-	if (!kvm_is_gpa_in_memslot(kvm, mop->gaddr)) {
-		r = PGM_ADDRESSING;
-		goto out_unlock;
-	}
+	scoped_guard(srcu, &kvm->srcu) {
+		if (!kvm_is_gpa_in_memslot(kvm, mop->gaddr))
+			return PGM_ADDRESSING;
 
-	acc_mode = mop->op == KVM_S390_MEMOP_ABSOLUTE_READ ? GACC_FETCH : GACC_STORE;
-	if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY) {
-		r = check_gpa_range(kvm, mop->gaddr, mop->size, acc_mode, mop->key);
-		goto out_unlock;
-	}
-	if (acc_mode == GACC_FETCH) {
+		if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY)
+			return check_gpa_range(kvm, mop->gaddr, mop->size, acc_mode, mop->key);
+
+		if (acc_mode == GACC_STORE && copy_from_user(tmpbuf, uaddr, mop->size))
+			return -EFAULT;
 		r = access_guest_abs_with_key(kvm, mop->gaddr, tmpbuf,
-					      mop->size, GACC_FETCH, mop->key);
+					      mop->size, acc_mode, mop->key);
 		if (r)
-			goto out_unlock;
-		if (copy_to_user(uaddr, tmpbuf, mop->size))
-			r = -EFAULT;
-	} else {
-		if (copy_from_user(tmpbuf, uaddr, mop->size)) {
-			r = -EFAULT;
-			goto out_unlock;
-		}
-		r = access_guest_abs_with_key(kvm, mop->gaddr, tmpbuf,
-					      mop->size, GACC_STORE, mop->key);
+			return r;
+		if (acc_mode != GACC_STORE && copy_to_user(uaddr, tmpbuf, mop->size))
+			return -EFAULT;
 	}
 
-out_unlock:
-	srcu_read_unlock(&kvm->srcu, srcu_idx);
-
-	vfree(tmpbuf);
-	return r;
+	return 0;
 }
 
 static int kvm_s390_vm_mem_op_cmpxchg(struct kvm *kvm, struct kvm_s390_mem_op *mop)
 {
 	void __user *uaddr = (void __user *)mop->buf;
 	void __user *old_addr = (void __user *)mop->old_addr;
-	union {
-		__uint128_t quad;
-		char raw[sizeof(__uint128_t)];
-	} old = { .quad = 0}, new = { .quad = 0 };
-	unsigned int off_in_quad = sizeof(new) - mop->size;
-	int r, srcu_idx;
-	bool success;
+	union kvm_s390_quad old = { .sixteen = 0 };
+	union kvm_s390_quad new = { .sixteen = 0 };
+	bool success = false;
+	int r;
 
 	r = mem_op_validate_common(mop, KVM_S390_MEMOP_F_SKEY_PROTECTION);
 	if (r)
@@ -2972,25 +2956,21 @@ static int kvm_s390_vm_mem_op_cmpxchg(struct kvm *kvm, struct kvm_s390_mem_op *m
 	 */
 	if (mop->size > sizeof(new))
 		return -EINVAL;
-	if (copy_from_user(&new.raw[off_in_quad], uaddr, mop->size))
+	if (copy_from_user(&new, uaddr, mop->size))
 		return -EFAULT;
-	if (copy_from_user(&old.raw[off_in_quad], old_addr, mop->size))
+	if (copy_from_user(&old, old_addr, mop->size))
 		return -EFAULT;
 
-	srcu_idx = srcu_read_lock(&kvm->srcu);
+	scoped_guard(srcu, &kvm->srcu) {
+		if (!kvm_is_gpa_in_memslot(kvm, mop->gaddr))
+			return PGM_ADDRESSING;
 
-	if (!kvm_is_gpa_in_memslot(kvm, mop->gaddr)) {
-		r = PGM_ADDRESSING;
-		goto out_unlock;
-	}
-
-	r = cmpxchg_guest_abs_with_key(kvm, mop->gaddr, mop->size, &old.quad,
-				       new.quad, mop->key, &success);
-	if (!success && copy_to_user(old_addr, &old.raw[off_in_quad], mop->size))
-		r = -EFAULT;
+		r = cmpxchg_guest_abs_with_key(kvm, mop->gaddr, mop->size, &old, new,
+					       mop->key, &success);
 
-out_unlock:
-	srcu_read_unlock(&kvm->srcu, srcu_idx);
+		if (!success && copy_to_user(old_addr, &old, mop->size))
+			return -EFAULT;
+	}
 	return r;
 }
 

arch/s390/kvm/kvm-s390.h

@@ -22,6 +22,14 @@
 
 #define KVM_S390_UCONTROL_MEMSLOT (KVM_USER_MEM_SLOTS + 0)
 
+union kvm_s390_quad {
+	__uint128_t sixteen;
+	unsigned long eight;
+	unsigned int four;
+	unsigned short two;
+	unsigned char one;
+};
+
 static inline void kvm_s390_fpu_store(struct kvm_run *run)
 {
 	fpu_stfpc(&run->s.regs.fpc);