[PATCH]: kvm-s390: add KVM_S390_GET/SET_SREGS2 call for additional hw regs

[Christian Borntraeger <borntraeger@de.ibm.com>]

Avi, Marcelo,

let me know if you would prefer to reuse another register load/save ioctls
that is still unused for s390 (e.g. XCRS).


From: Christian Borntraeger <borntraeger@de.ibm.com>

For guest relocation and virsh dump qemu needs an interface to
get/set additional registers from kvm. We also need the prefix
register for all guest memory accesses to the prefix pages.

The prefix register could also be set via the KVM_S390_SIGP_SET_PREFIX
interrupt ioctl, but I also added the synchronous operation to have

o symmetry: we want to have the same struct for get/set routine
o the interrupt is only delivered before entering the SIE, we also
  want to cover the sequence set prefix/store status at prefix

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
 arch/s390/include/asm/kvm.h |    9 +++++++++
 arch/s390/kvm/kvm-s390.c    |   24 ++++++++++++++++++++++++
 include/linux/kvm.h         |    4 ++++
 3 files changed, 37 insertions(+)

Index: b/arch/s390/include/asm/kvm.h
===================================================================
--- a/arch/s390/include/asm/kvm.h
+++ b/arch/s390/include/asm/kvm.h
@@ -28,6 +28,15 @@ struct kvm_sregs {
 	__u64 crs[16];
 };
 
+/* for KVM_S390_GET_SREGS2 and KVM_S390_SET_SREGS2 */
+struct kvm_s390_sregs2 {
+	__u64 ckc;
+	__u64 cputm;
+	__u64 gbea;
+	__u32 todpr;
+	__u32 prefix;
+};
+
 /* for KVM_GET_FPU and KVM_SET_FPU */
 struct kvm_fpu {
 	__u32 fpc;
Index: b/arch/s390/kvm/kvm-s390.c
===================================================================
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -129,6 +129,7 @@ int kvm_dev_ioctl_check_extension(long e
 	case KVM_CAP_S390_PSW:
 	case KVM_CAP_S390_GMAP:
 	case KVM_CAP_SYNC_MMU:
+	case KVM_CAP_S390_SREGS2:
 		r = 1;
 		break;
 	default:
@@ -673,6 +674,29 @@ long kvm_arch_vcpu_ioctl(struct file *fi
 	case KVM_S390_INITIAL_RESET:
 		r = kvm_arch_vcpu_ioctl_initial_reset(vcpu);
 		break;
+	case KVM_S390_GET_SREGS2: {
+		struct kvm_s390_sregs2 sregs2;
+
+		sregs2.prefix = vcpu->arch.sie_block->prefix;
+		sregs2.gbea = vcpu->arch.sie_block->gbea;
+		sregs2.cputm = vcpu->arch.sie_block->cputm;
+		sregs2.ckc = vcpu->arch.sie_block->ckc;
+		sregs2.todpr = vcpu->arch.sie_block->todpr;
+		r = copy_to_user(argp, &sregs2, sizeof(sregs2));
+		break;
+	}
+	case KVM_S390_SET_SREGS2: {
+		struct kvm_s390_sregs2 sregs2;
+
+		vcpu->arch.sie_block->prefix = sregs2.prefix;
+		vcpu->arch.sie_block->gbea = sregs2.gbea;
+		vcpu->arch.sie_block->cputm = sregs2.cputm;
+		vcpu->arch.sie_block->ckc = sregs2.ckc;
+		vcpu->arch.sie_block->todpr = sregs2.todpr;
+		r = copy_from_user(&sregs2, argp, sizeof(sregs2));
+	        vcpu->arch.sie_block->ihcpu     = 0xffff;
+		break;
+	}
 	default:
 		r = -EINVAL;
 	}
Index: b/include/linux/kvm.h
===================================================================
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -557,6 +557,7 @@ struct kvm_ppc_pvinfo {
 #define KVM_CAP_MAX_VCPUS 66       /* returns max vcpus per vm */
 #define KVM_CAP_PPC_PAPR 68
 #define KVM_CAP_S390_GMAP 71
+#define KVM_CAP_S390_SREGS2 72
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -762,6 +763,9 @@ struct kvm_clock_data {
 #define KVM_CREATE_SPAPR_TCE	  _IOW(KVMIO,  0xa8, struct kvm_create_spapr_tce)
 /* Available with KVM_CAP_RMA */
 #define KVM_ALLOCATE_RMA	  _IOR(KVMIO,  0xa9, struct kvm_allocate_rma)
+/* Available with KVM_CAP_S390_SREGS2 */
+#define KVM_S390_GET_SREGS2        _IOR(KVMIO,  0xaa, struct kvm_s390_sregs2)
+#define KVM_S390_SET_SREGS2        _IOW(KVMIO,  0xab, struct kvm_s390_sregs2)
 
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)