On Wed, 8 Aug 2018 11:33:23 +0200 Auger Eric <eric.au...@redhat.com> wrote:
> Hi Igor, > > On 07/18/2018 03:00 PM, Igor Mammedov wrote: > [...] > >>> > >>> I think Igor wants one contiguous region for RAM, where additional > >>> space can be reserved for hotplugging. > >> This is not compliant with 2012 ARM white paper, although I don't really > >> know if this document truly is a reference (did not get any reply). > > it's upto QEMU to pick layout, if we have maxmem (upto 256Gb) we could > > accommodate legacy req and put single device_memory in 1Gb-256Gb GPA gap, > > if it's more we can move whole device_memory to 2Tb, 8Tb ... > > that keeps things manageable for us and fits specs (if such exist). > > WE should make selection of the next RAM base deterministic is possible > > when layout changes due to maxram size or IOVA, so that we won't need > > to use compat knobs/checks to keep machine migratable. > Sorry for the delay. I was out of the office those past weeks. > > OK understood. Your preferred approach is to have a contiguous memory > region (initial + hotplug). So this depends on the FW capability to > support flexible RAM base. Let's see how this dependency gets resolved. I think Drew had already a look at FW side of the issue and has a prototype to works with. Once he's back in the office he planned to work on upstreaming EDK and qemu parts. > This series does not bump the non hotpluggable memory region limit, > which is still limited to 255GB. The only way to add more memory is > though PCDIMM or NVDIMM (max 2TB atm). To do so you need to add ,maxmem > and ,slots options which need to be on both source and dest, right, + > the PCDIMM/NVDIMM device option lines? Also the series checks the > destination has at least the same IPA range capability as the source, > which conditions the fact the requested device_memory size can be > accommodated. At the moment I fail to see what are the other compat > knobs I must be prepared to handle. it looks the same to me. We might use presence of slot/maxmem options as a knob to switch to a new all DIMM layout (initial + hotplug) with floating ram base. That way guests/fw that are designed to work with fixed RAM base will work just fine by default and guests/fw that are to work with mem hotplug or large RAM need vfio holes will use floating RAM base. Does it seem reasonable? > Thanks > > Eric > > > > [...] > >
