On Mon, 2020-03-23 at 14:24 +1100, David Gibson wrote: > On Fri, Mar 20, 2020 at 09:39:22PM -0300, Leonardo Bras wrote: > > Add support for MinMem SPLPAR Characteristic on emulated > > RTAS call ibm,get-system-parameter. > > > > MinMem represents Minimum Memory, that is described in LOPAPR as: > > The minimum amount of main store that is needed to power on the > > partition. Minimum memory is expressed in MB of storage. > > Where exactly does LoPAPR say that? The version I'm looking at > doesn't describe MinMem all that clearly, other than to say it must be > <= DesMem, which currently has the same value here.
Please look for "Minimum Memory". It's on Table 237. SPLPAR Terms. > > This provides a way for the OS to discern hotplugged LMBs and > > LMBs that have started with the VM, allowing it to better provide > > a way for memory hot-removal. > > This seems a bit dubious. Surely we should have this information from > the dynamic-reconfiguration-memory stuff already? Trying to discern > this from purely a number seems very fragile - wouldn't that mean > making assumptions about how qemu / the host is laying out it's fixed > and dynamic memory which might not be justified? I agree. I previously sent a RFC proposing the usage of a new flag for this same reason [1], which I thank you for positive feedback. Even though I think using a flag is a better solution, I am also working in this other option (MinMem), that would use parameter already available on the platform, in case the new flag don't get approved. So far, using MinMem looks like a very complex solution on kernel side, and I think it's a poor solution. I decided to send this patch because it's a simple change to the platform support, that should cause no harm and could even be useful to other OSes. Best regards, Leonardo [1] http://patchwork.ozlabs.org/patch/1249931/
signature.asc
Description: This is a digitally signed message part