On Sat, Jan 04, 2020 at 11:54:21PM +0100, Klemens Nanni wrote: > The hypervisor requires memory and allocates it transparently, e.g. on > my T4-2 with 128G in factory-default configuration without guests, the > primary domain boots into OBP with 127.5G while the PRI presents 127.62M > of physical memory available. > > Documentation about those machine dependent allocations seems scarse, > I haven't found any so far except for M10/M12 machines of which I don't > even know whether OpenBSD would boot on them. > > ldomctl works with what it gets from the PRI and some configurations > (nearly) exhausting the available memory may fail to boot as the > hypervisor rejects the configuration, sadly with all too generic memory > related warnings. > > Can we highlight these circumstances under BUGS? I think it helps to > shed some light on this until we find proper documentation to fix this > or some way to handle this from within ldomctl. > > Feedback? OK? Opinions on this?
I'll probably put this in during the next week unless I hear objections; this information seems valuable for users and also serves as reminder each time I look at the manual. Index: ldom.conf.5 =================================================================== RCS file: /cvs/src/usr.sbin/ldomctl/ldom.conf.5,v retrieving revision 1.9 diff -u -p -r1.9 ldom.conf.5 --- ldom.conf.5 3 Dec 2019 21:07:03 -0000 1.9 +++ ldom.conf.5 12 Jan 2020 10:43:35 -0000 @@ -107,3 +107,18 @@ On a machine with 32 cores and 64GB phys .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 Em 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.
