KVM: s390: Wire up ioeventfd.

Enable ioeventfd support on s390 and hook up diagnose 500 virtio-ccw
notifications.
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/s390/kvm/Kconfig

@@ -22,6 +22,7 @@ config KVM
 	select PREEMPT_NOTIFIERS
 	select ANON_INODES
 	select HAVE_KVM_CPU_RELAX_INTERCEPT
+	select HAVE_KVM_EVENTFD
 	---help---
 	  Support hosting paravirtualized guest machines using the SIE
 	  virtualization capability on the mainframe. This should work

arch/s390/kvm/Makefile

@@ -6,7 +6,7 @@
 # it under the terms of the GNU General Public License (version 2 only)
 # as published by the Free Software Foundation.
 
-common-objs = $(addprefix ../../../virt/kvm/, kvm_main.o)
+common-objs = $(addprefix ../../../virt/kvm/, kvm_main.o eventfd.o)
 
 ccflags-y := -Ivirt/kvm -Iarch/s390/kvm
 

arch/s390/kvm/diag.c

@@ -13,6 +13,7 @@
 
 #include <linux/kvm.h>
 #include <linux/kvm_host.h>
+#include <asm/virtio-ccw.h>
 #include "kvm-s390.h"
 #include "trace.h"
 #include "trace-s390.h"
@@ -104,6 +105,29 @@ static int __diag_ipl_functions(struct kvm_vcpu *vcpu)
 	return -EREMOTE;
 }
 
+static int __diag_virtio_hypercall(struct kvm_vcpu *vcpu)
+{
+	int ret, idx;
+
+	/* No virtio-ccw notification? Get out quickly. */
+	if (!vcpu->kvm->arch.css_support ||
+	    (vcpu->run->s.regs.gprs[1] != KVM_S390_VIRTIO_CCW_NOTIFY))
+		return -EOPNOTSUPP;
+
+	idx = srcu_read_lock(&vcpu->kvm->srcu);
+	/*
+	 * The layout is as follows:
+	 * - gpr 2 contains the subchannel id (passed as addr)
+	 * - gpr 3 contains the virtqueue index (passed as datamatch)
+	 */
+	ret = kvm_io_bus_write(vcpu->kvm, KVM_VIRTIO_CCW_NOTIFY_BUS,
+				vcpu->run->s.regs.gprs[2],
+				8, &vcpu->run->s.regs.gprs[3]);
+	srcu_read_unlock(&vcpu->kvm->srcu, idx);
+	/* kvm_io_bus_write returns -EOPNOTSUPP if it found no match. */
+	return ret < 0 ? ret : 0;
+}
+
 int kvm_s390_handle_diag(struct kvm_vcpu *vcpu)
 {
 	int code = (vcpu->arch.sie_block->ipb & 0xfff0000) >> 16;
@@ -118,6 +142,8 @@ int kvm_s390_handle_diag(struct kvm_vcpu *vcpu)
 		return __diag_time_slice_end_directed(vcpu);
 	case 0x308:
 		return __diag_ipl_functions(vcpu);
+	case 0x500:
+		return __diag_virtio_hypercall(vcpu);
 	default:
 		return -EOPNOTSUPP;
 	}

arch/s390/kvm/kvm-s390.c

@@ -142,6 +142,7 @@ int kvm_dev_ioctl_check_extension(long ext)
 	case KVM_CAP_ONE_REG:
 	case KVM_CAP_ENABLE_CAP:
 	case KVM_CAP_S390_CSS_SUPPORT:
+	case KVM_CAP_IOEVENTFD:
 		r = 1;
 		break;
 	case KVM_CAP_NR_VCPUS: