[GIT PULL 15/18] KVM: s390: usage hint for adapter mappings

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From: Cornelia Huck <cornelia.huck@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
 Documentation/virtual/kvm/devices/s390_flic.txt | 2 ++
 1 file changed, 2 insertions(+)

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 @@ struct kvm_s390_io_adapter_req {
       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
-- 
2.3.0

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