KVM: s390: interprocessor communication via sigp

This patch introduces in-kernel handling of _some_ sigp interprocessor
signals (similar to ipi).
kvm_s390_handle_sigp() decodes the sigp instruction and calls individual
handlers depending on the operation requested:
- sigp sense tries to retrieve information such as existence or running state
  of the remote cpu
- sigp emergency sends an external interrupt to the remove cpu
- sigp stop stops a remove cpu
- sigp stop store status stops a remote cpu, and stores its entire internal
  state to the cpus lowcore
- sigp set arch sets the architecture mode of the remote cpu. setting to
  ESAME (s390x 64bit) is accepted, setting to ESA/S390 (s390, 31 or 24 bit) is
  denied, all others are passed to userland
- sigp set prefix sets the prefix register of a remote cpu

For implementation of this, the stop intercept indication starts to get reused
on purpose: a set of action bits defines what to do once a cpu gets stopped:
ACTION_STOP_ON_STOP  really stops the cpu when a stop intercept is recognized
ACTION_STORE_ON_STOP stores the cpu status to lowcore when a stop intercept is
                     recognized

Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 20 insertions, 2 deletions

diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index 7a20d63..9f0d8b2 100644
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -95,6 +95,7 @@ static int handle_lctl(struct kvm_vcpu *vcpu)
 }
 
 static intercept_handler_t instruction_handlers[256] = {
+	[0xae] = kvm_s390_handle_sigp,
 	[0xb2] = kvm_s390_handle_priv,
 	[0xb7] = handle_lctl,
 	[0xeb] = handle_lctg,
@@ -117,10 +118,27 @@ static int handle_noop(struct kvm_vcpu *vcpu)
 
 static int handle_stop(struct kvm_vcpu *vcpu)
 {
+	int rc;
+
 	vcpu->stat.exit_stop_request++;
-	VCPU_EVENT(vcpu, 3, "%s", "cpu stopped");
 	atomic_clear_mask(CPUSTAT_RUNNING, &vcpu->arch.sie_block->cpuflags);
-	return -ENOTSUPP;
+	spin_lock_bh(&vcpu->arch.local_int.lock);
+	if (vcpu->arch.local_int.action_bits & ACTION_STORE_ON_STOP) {
+		vcpu->arch.local_int.action_bits &= ~ACTION_STORE_ON_STOP;
+		rc = __kvm_s390_vcpu_store_status(vcpu,
+						  KVM_S390_STORE_STATUS_NOADDR);
+		if (rc >= 0)
+			rc = -ENOTSUPP;
+	}
+
+	if (vcpu->arch.local_int.action_bits & ACTION_STOP_ON_STOP) {
+		vcpu->arch.local_int.action_bits &= ~ACTION_STOP_ON_STOP;
+		VCPU_EVENT(vcpu, 3, "%s", "cpu stopped");
+		rc = -ENOTSUPP;
+	} else
+		rc = 0;
+	spin_unlock_bh(&vcpu->arch.local_int.lock);
+	return rc;
 }
 
 static int handle_validity(struct kvm_vcpu *vcpu)