KVM: s390: Add optional storage key checking to MEMOP IOCTL

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>

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index fdbd6c1dc709aa2f3391609de621c18a8cec08aa..c31b40abfa238d5aac84b6fb5943e63ce3885798 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2359,6 +2359,11 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
        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)
 {
@@ -4692,17 +4697,21 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
        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)
@@ -4712,11 +4721,12 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
        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;
@@ -4724,15 +4734,16 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
                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;
        }
 

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 5191b57e156220bd7fc6d85940c301e16cc1645a..4566f429db2c8cd53009e996b9b34439f00427e4 100644 (file)
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -562,7 +562,10 @@ 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 */
        };
@@ -575,6 +578,7 @@ 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 {