KVM: s390: introduce ais mode modify function

Provide an interface for userspace to modify AIS
(adapter-interruption-suppression) mode state, and add documentation
for the interface. Allowed target modes are ALL-Interruptions mode
and SINGLE-Interruption mode.

We introduce the 'simm' and 'nimm' fields in kvm_s390_float_interrupt
to store interruption modes for each ISC. Each bit in 'simm' and
'nimm' targets to one ISC, and collaboratively indicate three modes:
ALL-Interruptions, SINGLE-Interruption and NO-Interruptions. This
interface can initiate most transitions between the states; transition
from SINGLE-Interruption to NO-Interruptions via adapter interrupt
injection will be introduced in a following patch. The meaningful
combinations are as follows:

    interruption mode | simm bit | nimm bit
    ------------------|----------|----------
             ALL      |    0     |     0
           SINGLE     |    1     |     0
             NO       |    1     |     1

Besides, add tracepoint to track AIS mode transitions.

Co-Authored-By: Yi Min Zhao <zyimin@linux.vnet.ibm.com>
Signed-off-by: Yi Min Zhao <zyimin@linux.vnet.ibm.com>
Signed-off-by: Fei Li <sherrylf@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

Documentation/virtual/kvm/devices/s390_flic.txt

@@ -14,6 +14,7 @@ FLIC provides support to
 - purge one pending floating I/O interrupt (KVM_DEV_FLIC_CLEAR_IO_IRQ)
 - enable/disable for the guest transparent async page faults
 - register and modify adapter interrupt sources (KVM_DEV_FLIC_ADAPTER_*)
+- modify AIS (adapter-interruption-suppression) mode state (KVM_DEV_FLIC_AISM)
 
 Groups:
   KVM_DEV_FLIC_ENQUEUE
@@ -107,6 +108,25 @@ struct kvm_s390_io_adapter_req {
       release a userspace page for the translated address specified in addr
       from the list of mappings
 
+  KVM_DEV_FLIC_AISM
+    modify the adapter-interruption-suppression mode for a given isc if the
+    AIS capability is enabled. Takes a kvm_s390_ais_req describing:
+
+struct kvm_s390_ais_req {
+	__u8 isc;
+	__u16 mode;
+};
+
+    isc contains the target I/O interruption subclass, mode the target
+    adapter-interruption-suppression mode. The following modes are
+    currently supported:
+    - KVM_S390_AIS_MODE_ALL: ALL-Interruptions Mode, i.e. airq injection
+      is always allowed;
+    - KVM_S390_AIS_MODE_SINGLE: SINGLE-Interruption Mode, i.e. airq
+      injection is only allowed once and the following adapter interrupts
+      will be suppressed until the mode is set again to ALL-Interruptions
+      or SINGLE-Interruption mode.
+
 Note: The KVM_SET_DEVICE_ATTR/KVM_GET_DEVICE_ATTR device ioctls executed on
 FLIC with an unknown group or attribute gives the error code EINVAL (instead of
 ENXIO, as specified in the API documentation). It is not possible to conclude

arch/s390/include/asm/kvm_host.h

@@ -521,6 +521,12 @@ struct kvm_s390_local_interrupt {
 #define FIRQ_CNTR_PFAULT   3
 #define FIRQ_MAX_COUNT     4
 
+/* mask the AIS mode for a given ISC */
+#define AIS_MODE_MASK(isc) (0x80 >> isc)
+
+#define KVM_S390_AIS_MODE_ALL    0
+#define KVM_S390_AIS_MODE_SINGLE 1
+
 struct kvm_s390_float_interrupt {
 	unsigned long pending_irqs;
 	spinlock_t lock;
@@ -530,6 +536,10 @@ struct kvm_s390_float_interrupt {
 	struct kvm_s390_ext_info srv_signal;
 	int next_rr_cpu;
 	unsigned long idle_mask[BITS_TO_LONGS(KVM_MAX_VCPUS)];
+	struct mutex ais_lock;
+	u8 simm;
+	u8 nimm;
+	int ais_enabled;
 };
 
 struct kvm_hw_wp_info_arch {

arch/s390/include/uapi/asm/kvm.h

@@ -26,6 +26,7 @@
 #define KVM_DEV_FLIC_ADAPTER_REGISTER	6
 #define KVM_DEV_FLIC_ADAPTER_MODIFY	7
 #define KVM_DEV_FLIC_CLEAR_IO_IRQ	8
+#define KVM_DEV_FLIC_AISM		9
 /*
  * We can have up to 4*64k pending subchannels + 8 adapter interrupts,
  * as well as up  to ASYNC_PF_PER_VCPU*KVM_MAX_VCPUS pfault done interrupts.
@@ -46,6 +47,11 @@ struct kvm_s390_io_adapter {
 
 #define KVM_S390_ADAPTER_SUPPRESSIBLE 0x01
 
+struct kvm_s390_ais_req {
+	__u8 isc;
+	__u16 mode;
+};
+
 #define KVM_S390_IO_ADAPTER_MASK 1
 #define KVM_S390_IO_ADAPTER_MAP 2
 #define KVM_S390_IO_ADAPTER_UNMAP 3

arch/s390/kvm/interrupt.c

@@ -2152,6 +2152,45 @@ static int clear_io_irq(struct kvm *kvm, struct kvm_device_attr *attr)
 	return 0;
 }
 
+static int modify_ais_mode(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	struct kvm_s390_float_interrupt *fi = &kvm->arch.float_int;
+	struct kvm_s390_ais_req req;
+	int ret = 0;
+
+	if (!fi->ais_enabled)
+		return -ENOTSUPP;
+
+	if (copy_from_user(&req, (void __user *)attr->addr, sizeof(req)))
+		return -EFAULT;
+
+	if (req.isc > MAX_ISC)
+		return -EINVAL;
+
+	trace_kvm_s390_modify_ais_mode(req.isc,
+				       (fi->simm & AIS_MODE_MASK(req.isc)) ?
+				       (fi->nimm & AIS_MODE_MASK(req.isc)) ?
+				       2 : KVM_S390_AIS_MODE_SINGLE :
+				       KVM_S390_AIS_MODE_ALL, req.mode);
+
+	mutex_lock(&fi->ais_lock);
+	switch (req.mode) {
+	case KVM_S390_AIS_MODE_ALL:
+		fi->simm &= ~AIS_MODE_MASK(req.isc);
+		fi->nimm &= ~AIS_MODE_MASK(req.isc);
+		break;
+	case KVM_S390_AIS_MODE_SINGLE:
+		fi->simm |= AIS_MODE_MASK(req.isc);
+		fi->nimm &= ~AIS_MODE_MASK(req.isc);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+	mutex_unlock(&fi->ais_lock);
+
+	return ret;
+}
+
 static int flic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
 {
 	int r = 0;
@@ -2188,6 +2227,9 @@ static int flic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
 	case KVM_DEV_FLIC_CLEAR_IO_IRQ:
 		r = clear_io_irq(dev->kvm, attr);
 		break;
+	case KVM_DEV_FLIC_AISM:
+		r = modify_ais_mode(dev->kvm, attr);
+		break;
 	default:
 		r = -EINVAL;
 	}
@@ -2207,6 +2249,7 @@ static int flic_has_attr(struct kvm_device *dev,
 	case KVM_DEV_FLIC_ADAPTER_REGISTER:
 	case KVM_DEV_FLIC_ADAPTER_MODIFY:
 	case KVM_DEV_FLIC_CLEAR_IO_IRQ:
+	case KVM_DEV_FLIC_AISM:
 		return 0;
 	}
 	return -ENXIO;

arch/s390/kvm/kvm-s390.c

@@ -1515,6 +1515,10 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 
 	kvm_s390_crypto_init(kvm);
 
+	mutex_init(&kvm->arch.float_int.ais_lock);
+	kvm->arch.float_int.simm = 0;
+	kvm->arch.float_int.nimm = 0;
+	kvm->arch.float_int.ais_enabled = 0;
 	spin_lock_init(&kvm->arch.float_int.lock);
 	for (i = 0; i < FIRQ_LIST_COUNT; i++)
 		INIT_LIST_HEAD(&kvm->arch.float_int.lists[i]);

arch/s390/kvm/trace-s390.h

@@ -280,6 +280,37 @@ TRACE_EVENT(kvm_s390_enable_disable_ibs,
 		      __entry->state ? "enabling" : "disabling", __entry->id)
 	);
 
+/*
+ * Trace point for modifying ais mode for a given isc.
+ */
+TRACE_EVENT(kvm_s390_modify_ais_mode,
+	    TP_PROTO(__u8 isc, __u16 from, __u16 to),
+	    TP_ARGS(isc, from, to),
+
+	    TP_STRUCT__entry(
+		    __field(__u8, isc)
+		    __field(__u16, from)
+		    __field(__u16, to)
+		    ),
+
+	    TP_fast_assign(
+		    __entry->isc = isc;
+		    __entry->from = from;
+		    __entry->to = to;
+		    ),
+
+	    TP_printk("for isc %x, modifying interruption mode from %s to %s",
+		      __entry->isc,
+		      (__entry->from == KVM_S390_AIS_MODE_ALL) ?
+		      "ALL-Interruptions Mode" :
+		      (__entry->from == KVM_S390_AIS_MODE_SINGLE) ?
+		      "Single-Interruption Mode" : "No-Interruptions Mode",
+		      (__entry->to == KVM_S390_AIS_MODE_ALL) ?
+		      "ALL-Interruptions Mode" :
+		      (__entry->to == KVM_S390_AIS_MODE_SINGLE) ?
+		      "Single-Interruption Mode" : "No-Interruptions Mode")
+	);
+
 
 #endif /* _TRACE_KVMS390_H */