KVM: s390: add clear I/O irq operation for FLIC

Introduce a FLIC operation for clearing I/O interrupts for a subchannel.

Rationale: According to the platform specification, pending I/O
interruption requests have to be revoked in certain situations. For
instance, according to the Principles of Operation (page 17-27), a
subchannel put into the installed parameters initialized state is in the
same state as after an I/O system reset (just parameters possibly changed).
This implies that any I/O interrupts for that subchannel are no longer
pending (as I/O system resets clear I/O interrupts). Therefore, we need an
interface to clear pending I/O interrupts.

Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

diff --git a/Documentation/virtual/kvm/devices/s390_flic.txt b/Documentation/virtual/kvm/devices/s390_flic.txt
index 646f474..8478de1 100644 (file)
--- a/Documentation/virtual/kvm/devices/s390_flic.txt
+++ b/Documentation/virtual/kvm/devices/s390_flic.txt
@@ -11,6 +11,7 @@ FLIC provides support to
 - add interrupts (KVM_DEV_FLIC_ENQUEUE)
 - inspect currently pending interrupts (KVM_FLIC_GET_ALL_IRQS)
 - purge all pending floating interrupts (KVM_DEV_FLIC_CLEAR_IRQS)
+- 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_*)
 
@@ -40,6 +41,11 @@ Groups:
     Simply deletes all elements from the list of currently pending floating
     interrupts.  No interrupts are injected into the guest.
 
+  KVM_DEV_FLIC_CLEAR_IO_IRQ
+    Deletes one (if any) I/O interrupt for a subchannel identified by the
+    subsystem identification word passed via the buffer specified by
+    attr->addr (address) and attr->attr (length).
+
   KVM_DEV_FLIC_APF_ENABLE
     Enables async page faults for the guest. So in case of a major page fault
     the host is allowed to handle this async and continues the guest.

diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index 347fe5a..3b8e99e 100644 (file)
--- a/arch/s390/include/uapi/asm/kvm.h
+++ b/arch/s390/include/uapi/asm/kvm.h
@@ -25,6 +25,7 @@
 #define KVM_DEV_FLIC_APF_DISABLE_WAIT  5
 #define KVM_DEV_FLIC_ADAPTER_REGISTER  6
 #define KVM_DEV_FLIC_ADAPTER_MODIFY    7
+#define KVM_DEV_FLIC_CLEAR_IO_IRQ      8
 /*
  * 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.

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 4c2cdb2..e550404 100644 (file)
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -2034,6 +2034,27 @@ static int modify_io_adapter(struct kvm_device *dev,
        return ret;
 }
 
+static int clear_io_irq(struct kvm *kvm, struct kvm_device_attr *attr)
+
+{
+       const u64 isc_mask = 0xffUL << 24; /* all iscs set */
+       u32 schid;
+
+       if (attr->flags)
+               return -EINVAL;
+       if (attr->attr != sizeof(schid))
+               return -EINVAL;
+       if (copy_from_user(&schid, (void __user *) attr->addr, sizeof(schid)))
+               return -EFAULT;
+       kfree(kvm_s390_get_io_int(kvm, isc_mask, schid));
+       /*
+        * If userspace is conforming to the architecture, we can have at most
+        * one pending I/O interrupt per subchannel, so this is effectively a
+        * clear all.
+        */
+       return 0;
+}
+
 static int flic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
 {
        int r = 0;
@@ -2067,6 +2088,9 @@ static int flic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
        case KVM_DEV_FLIC_ADAPTER_MODIFY:
                r = modify_io_adapter(dev, attr);
                break;
+       case KVM_DEV_FLIC_CLEAR_IO_IRQ:
+               r = clear_io_irq(dev->kvm, attr);
+               break;
        default:
                r = -EINVAL;
        }
@@ -2085,6 +2109,7 @@ static int flic_has_attr(struct kvm_device *dev,
        case KVM_DEV_FLIC_APF_DISABLE_WAIT:
        case KVM_DEV_FLIC_ADAPTER_REGISTER:
        case KVM_DEV_FLIC_ADAPTER_MODIFY:
+       case KVM_DEV_FLIC_CLEAR_IO_IRQ:
                return 0;
        }
        return -ENXIO;