[PATCH v2 25/42] 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>
[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 cb58714fe60d..a82166e5f7d9 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, ONE_REG forbidden
+           for protected guests (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, ONE_REG forbidden
+           for protected guests (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 8db82aaf1275..d20a7fa9d480 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4638,6 +4638,9 @@ 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_is_protected(vcpu->kvm))
+			break;
 		r = -EFAULT;
 		if (copy_from_user(&reg, argp, sizeof(reg)))
 			break;
-- 
2.25.0