KVM: s390: usage hint for adapter mappings
The interface for adapter mappings was designed with code in mind
that maps each address only once; let's document this.
Otherwise, duplicate mappings are added to the list, which makes
the code ineffective and uses up the limited amount of mapping
needlessly.
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
diff --git a/Documentation/virtual/kvm/devices/s390_flic.txt b/Documentation/virtual/kvm/devices/s390_flic.txt
index d1ad9d5..e3e314c 100644
--- a/Documentation/virtual/kvm/devices/s390_flic.txt
+++ b/Documentation/virtual/kvm/devices/s390_flic.txt
@@ -88,6 +88,8 @@
perform a gmap translation for the guest address provided in addr,
pin a userspace page for the translated address and add it to the
list of mappings
+ Note: A new mapping will be created unconditionally; therefore,
+ the calling code should avoid making duplicate mappings.
KVM_S390_IO_ADAPTER_UNMAP
release a userspace page for the translated address specified in addr