virsh: Enhance documentation of --rdma-pin-all option

https://bugzilla.redhat.com/show_bug.cgi?id=1373783

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>

diff --git a/tools/virsh.pod b/tools/virsh.pod
index 4331c76fc72f68abf7a50c3f2035e53caa524d07..576f0c122889d463f1f69724052c84b9968acb63 100644 (file)
--- a/tools/virsh.pod
+++ b/tools/virsh.pod
@@ -1767,7 +1767,13 @@ periodically increased by I<auto-converge-increment>.
 
 I<--rdma-pin-all> can be used with RDMA migration (i.e., when I<migrateuri>
 starts with rdma://) to tell the hypervisor to pin all domain's memory at once
-before migration starts rather than letting it pin memory pages as needed.
+before migration starts rather than letting it pin memory pages as needed. For
+QEMU/KVM this requires hard_limit memory tuning element (in the domain XML) to
+be used and set to the maximum memory configured for the domain plus any memory
+consumed by the QEMU process itself. Beware of setting the memory limit too
+high (and thus allowing the domain to lock most of the host's memory). Doing so
+may be dangerous to both the domain and the host itself since the host's kernel
+may run out of memory.
 
 B<Note>: Individual hypervisors usually do not support all possible types of
 migration. For example, QEMU does not support direct migration.