From: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
Date: Fri, 11 Feb 2022 19:22:10 +0100
Subject: KVM: s390: Add optional storage key checking to MEMOP IOCTL
Git-commit: e9e9feebcbc14b174fef862842f8cc9a388e1db3
Patch-mainline: v5.18-rc1
References: jsc#PED-579

User space needs a mechanism to perform key checked accesses when
emulating instructions.

The key can be passed as an additional argument.
Having an additional argument is flexible, as user space can
pass the guest PSW's key, in order to make an access the same way the
CPU would, or pass another key if necessary.

Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/r/20220211182215.2730017-6-scgl@linux.ibm.com
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 arch/s390/kvm/kvm-s390.c |   31 +++++++++++++++++++++----------
 include/uapi/linux/kvm.h |    6 +++++-
 2 files changed, 26 insertions(+), 11 deletions(-)

--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2391,6 +2391,11 @@ static int kvm_s390_handle_pv(struct kvm
 	return r;
 }
 
+static bool access_key_invalid(u8 access_key)
+{
+	return access_key > 0xf;
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg)
 {
@@ -4713,17 +4718,21 @@ static long kvm_s390_guest_mem_op(struct
 	void *tmpbuf = NULL;
 	int r = 0;
 	const u64 supported_flags = KVM_S390_MEMOP_F_INJECT_EXCEPTION
-				    | KVM_S390_MEMOP_F_CHECK_ONLY;
+				    | KVM_S390_MEMOP_F_CHECK_ONLY
+				    | KVM_S390_MEMOP_F_SKEY_PROTECTION;
 
 	if (mop->flags & ~supported_flags || mop->ar >= NUM_ACRS || !mop->size)
 		return -EINVAL;
-
 	if (mop->size > MEM_OP_MAX_SIZE)
 		return -E2BIG;
-
 	if (kvm_s390_pv_cpu_is_protected(vcpu))
 		return -EINVAL;
-
+	if (mop->flags & KVM_S390_MEMOP_F_SKEY_PROTECTION) {
+		if (access_key_invalid(mop->key))
+			return -EINVAL;
+	} else {
+		mop->key = 0;
+	}
 	if (!(mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY)) {
 		tmpbuf = vmalloc(mop->size);
 		if (!tmpbuf)
@@ -4733,11 +4742,12 @@ static long kvm_s390_guest_mem_op(struct
 	switch (mop->op) {
 	case KVM_S390_MEMOP_LOGICAL_READ:
 		if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY) {
-			r = check_gva_range(vcpu, mop->gaddr, mop->ar,
-					    mop->size, GACC_FETCH, 0);
+			r = check_gva_range(vcpu, mop->gaddr, mop->ar, mop->size,
+					    GACC_FETCH, mop->key);
 			break;
 		}
-		r = read_guest(vcpu, mop->gaddr, mop->ar, tmpbuf, mop->size);
+		r = read_guest_with_key(vcpu, mop->gaddr, mop->ar, tmpbuf,
+					mop->size, mop->key);
 		if (r == 0) {
 			if (copy_to_user(uaddr, tmpbuf, mop->size))
 				r = -EFAULT;
@@ -4745,15 +4755,16 @@ static long kvm_s390_guest_mem_op(struct
 		break;
 	case KVM_S390_MEMOP_LOGICAL_WRITE:
 		if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY) {
-			r = check_gva_range(vcpu, mop->gaddr, mop->ar,
-					    mop->size, GACC_STORE, 0);
+			r = check_gva_range(vcpu, mop->gaddr, mop->ar, mop->size,
+					    GACC_STORE, mop->key);
 			break;
 		}
 		if (copy_from_user(tmpbuf, uaddr, mop->size)) {
 			r = -EFAULT;
 			break;
 		}
-		r = write_guest(vcpu, mop->gaddr, mop->ar, tmpbuf, mop->size);
+		r = write_guest_with_key(vcpu, mop->gaddr, mop->ar, tmpbuf,
+					 mop->size, mop->key);
 		break;
 	}
 
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -544,7 +544,10 @@ struct kvm_s390_mem_op {
 	__u32 op;		/* type of operation */
 	__u64 buf;		/* buffer in userspace */
 	union {
-		__u8 ar;	/* the access register number */
+		struct {
+			__u8 ar;	/* the access register number */
+			__u8 key;	/* access key, ignored if flag unset */
+		};
 		__u32 sida_offset; /* offset into the sida */
 		__u8 reserved[32]; /* should be set to 0 */
 	};
@@ -557,6 +560,7 @@ struct kvm_s390_mem_op {
 /* flags for kvm_s390_mem_op->flags */
 #define KVM_S390_MEMOP_F_CHECK_ONLY		(1ULL << 0)
 #define KVM_S390_MEMOP_F_INJECT_EXCEPTION	(1ULL << 1)
+#define KVM_S390_MEMOP_F_SKEY_PROTECTION	(1ULL << 2)
 
 /* for KVM_INTERRUPT */
 struct kvm_interrupt {