Add BUGS section for hypervisor memory requirement

The hypervisor transparently allocates memory it needs, but the specific
amount is machine dependent and not always documented or known.

Mention these details to prevent users from overcommitting memroy in their
configuration.

1 files changed, 17 insertions, 2 deletions

diff --git a/usr.sbin/ldomctl/ldom.conf.5 b/usr.sbin/ldomctl/ldom.conf.5
index daf4f1145d5..246c75fe860 100644
--- a/usr.sbin/ldomctl/ldom.conf.5
+++ b/usr.sbin/ldomctl/ldom.conf.5
@@ -1,4 +1,4 @@
-.\" $OpenBSD: ldom.conf.5,v 1.9 2019/12/03 21:07:03 kn Exp $
+.\" $OpenBSD: ldom.conf.5,v 1.10 2020/01/13 09:29:41 kn Exp $
 .\"
 .\" Copyright (c) 2012 Mark Kettenis <kettenis@openbsd.org>
 .\"
@@ -14,7 +14,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: December 3 2019 $
+.Dd $Mdocdate: January 13 2020 $
 .Dt LDOM.CONF 5 sparc64
 .Os
 .Sh NAME
@@ -107,3 +107,18 @@ On a machine with 32 cores and 64GB physical memory, this leaves 12 cores and
 .Xr eeprom 8 ,
 .Xr ldomctl 8 ,
 .Xr ldomd 8
+.Sh BUGS
+The hypervisor requires a machine dependent amount of physical memory that is
+reserved automatically.
+Although the Physical Resource Inventory
+.Pq PRI
+seems to account for this by presenting less available memory, using the entire
+amount via
+.Ic memory
+is not always successful, e.g. the hypervisor would reject the configuration and
+fallback to
+.Dq factory-default
+upon resetting the machine.
+.Pp
+If in doubt, leave enough memory unused for the hypervisor to reserve.
+On bigger T4 based machines, 1024 megabytes has proven to suffice.