[PATCH v4 23/36] KVM: s390: protvirt: disallow one_reg

[Christian Borntraeger <borntraeger@xxxxxxxxxx>]

From: Janosch Frank <frankja@xxxxxxxxxxxxx>

A lot of the registers are controlled by the Ultravisor and never
visible to KVM. Some fields in the sie control block are overlayed, like
gbea. As no known userspace uses the ONE_REG interface on s390 if sync
regs are available, no functionality is lost if it is disabled for
protected guests.

Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
[borntraeger@xxxxxxxxxx: patch merging, splitting, fixing]
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
 Documentation/virt/kvm/api.rst | 6 ++++--
 arch/s390/kvm/kvm-s390.c       | 3 +++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 97a72a53fa4b..7505d7a6c0d8 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -2117,7 +2117,8 @@ Errors:
 
   ======   ============================================================
   ENOENT   no such register
-  EINVAL   invalid register ID, or no such register
+  EINVAL   invalid register ID, or no such register or used with VMs in
+           protected virtualization mode on s390
   EPERM    (arm64) register access not allowed before vcpu finalization
   ======   ============================================================
 
@@ -2552,7 +2553,8 @@ Errors include:
 
   ======== ============================================================
   ENOENT   no such register
-  EINVAL   invalid register ID, or no such register
+  EINVAL   invalid register ID, or no such register or used with VMs in
+           protected virtualization mode on s390
   EPERM    (arm64) register access not allowed before vcpu finalization
   ======== ============================================================
 
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 67a746b0f8b9..6ab4c88f2e1d 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4670,6 +4670,9 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 	case KVM_SET_ONE_REG:
 	case KVM_GET_ONE_REG: {
 		struct kvm_one_reg reg;
+		r = -EINVAL;
+		if (kvm_s390_pv_cpu_is_protected(vcpu))
+			break;
 		r = -EFAULT;
 		if (copy_from_user(&reg, argp, sizeof(reg)))
 			break;
-- 
2.25.0