KVM: s390: provide the prefix register via kvm_run

Add the prefix register to the synced register field in kvm_run.
While we need the prefix register most of the time read-only, this
patch also adds handling for guest dirtying of the prefix register.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

2 files changed, 9 insertions, 0 deletions

diff --git a/arch/s390/include/asm/kvm.h b/arch/s390/include/asm/kvm.h
index 325560afb77..9fc328c2615 100644
--- a/arch/s390/include/asm/kvm.h
+++ b/arch/s390/include/asm/kvm.h
@@ -41,7 +41,9 @@ struct kvm_debug_exit_arch {
 struct kvm_guest_debug_arch {
 };
 
+#define KVM_SYNC_PREFIX (1UL << 0)
 /* definition of registers in kvm_run */
 struct kvm_sync_regs {
+        __u64 prefix;   /* prefix register */
 };
 #endif
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 1868b89a840..6962c1b9eec 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -132,6 +132,7 @@ int kvm_dev_ioctl_check_extension(long ext)
 #ifdef CONFIG_KVM_S390_UCONTROL
         case KVM_CAP_S390_UCONTROL:
 #endif
+        case KVM_CAP_SYNC_REGS:
                 r = 1;
                 break;
         default:
@@ -288,6 +289,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
         }
 
         vcpu->arch.gmap = vcpu->kvm->arch.gmap;
+        vcpu->run->kvm_valid_regs = KVM_SYNC_PREFIX;
         return 0;
 }
 
@@ -572,6 +574,10 @@ rerun_vcpu:
 
         vcpu->arch.sie_block->gpsw.mask = kvm_run->psw_mask;
         vcpu->arch.sie_block->gpsw.addr = kvm_run->psw_addr;
+        if (kvm_run->kvm_dirty_regs & KVM_SYNC_PREFIX) {
+                kvm_run->kvm_dirty_regs &= ~KVM_SYNC_PREFIX;
+                kvm_s390_set_prefix(vcpu, kvm_run->s.regs.prefix);
+        }
 
         might_fault();
 
@@ -620,6 +626,7 @@ rerun_vcpu:
 
         kvm_run->psw_mask     = vcpu->arch.sie_block->gpsw.mask;
         kvm_run->psw_addr     = vcpu->arch.sie_block->gpsw.addr;
+        kvm_run->s.regs.prefix = vcpu->arch.sie_block->prefix;
 
         if (vcpu->sigset_active)
                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);