Hi Drew, On 06/15/2018 05:44 PM, Andrew Jones wrote: > On Tue, Jun 05, 2018 at 07:49:44AM +0000, Shameerali Kolothum Thodi wrote: >>>> On 05/16/2018 05:20 PM, Shameer Kolothum wrote: >>>>> In case valid iova regions are non-contiguous, split the >>>>> RAM mem into a 1GB non-pluggable dimm and remaining as a >>>>> single pc-dimm mem. >>>> >>>> Please can you explain where does this split come from? Currently we >>>> have 254 GB non pluggable RAM. I read the discussion started with Drew >>>> on RFC v1 where he explained we cannot change the RAM base without >>>> crashing the FW. However we should at least document this 1GB split. >>> >>> The comments were mainly to use the pc-dimm model instead of "mem alias" >>> method used on RFC v1 as this will help to add the mem hot-plug support >>> in future. >>> >>> I am not sure about the motive behind Drew's idea of splitting the first >>> 1GB as non-plug and remaining as a pc-dimm(cold). May it is to attempt a >>> best effort scenario, but as I mentioned in reply to 0/6, the current >>> solution >>> will end up changing the base address if the 0x4000000 falls under a >>> reserved >>> region. >>> >>> Again, not sure whether we should enforce a strict check on base address >>> start or just warn the user that it will fail on Guest with UEFI boot[1]. >>> >>> Hi Drew, >>> >>> Please let me know your thoughts on this. >> >> Could you please take a look at the above discussion and let us >> know your thoughts on the split of mem regions as 1GB non-pluggable >> and rest as pc-dimm. >> > > Hi Shameer, > > Sorry for the slow reply - I've been slowly catching back up after > vacation. There are two reasons to have one non-pluggable memory region > and the rest of memory in a single pluggable pc-dimm. > > 1) For mach-virt we must have the base of memory at the 1G boundary, > both because otherwise we'll break ArmVirt UEFI and because that's > a guarantee that Peter has stated he'd like to keep for mach-virt. > > 2) Memory split in this way already has precedent in the x86 PC > machine models. > > It's debatable how much memory we should allocate to the non-pluggable > region. It doesn't need to be 1G, it could be smaller. The default > memory size allocated to a mach-virt guest that doesn't provide '-m' > on the command line is 128M. Maybe we should use that size? > > If 0x40000000 falls into a reserved address region on some host, then > I'm afraid the mach-virt model won't work with those devices unless the > guest doesn't use UEFI and Peter is open to providing a machine property > that one can enable in order to move the base address of memory. > > I know Eric is looking at this problem too. I hope you guys are > coordinating your efforts.
Yes we sync'ed together. I will send an RFC beginning of next week addressing both - support of >40b PA VM (based on Suzuki's series) - addition of DIMM at 2TB, reusing the standard PC-DIMM hotplug framework. This is something standard and similar to what is done on PC Q35. I am reusing some of Shameer's patches, rebased on top of Igor and David recent works. Then we need to understand how we can use 2 hotplug regions. This is not obvsious to me as the framework currently uses a dedicated MemoryRegion, if I understand it correctly. Thanks Eric > > Thanks, > drew >
