On Fri, Feb 19, 2016 at 12:08 AM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > On Thu, Feb 18, 2016 at 11:05:23AM +0100, Igor Mammedov wrote: >> On Thu, 18 Feb 2016 12:03:36 +0800 >> Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx> wrote: >> >> > On 02/18/2016 01:26 AM, Michael S. Tsirkin wrote: >> > > On Wed, Feb 17, 2016 at 10:04:18AM +0800, Xiao Guangrong wrote: >> > >>>>> As for the rest could that commands go via MMIO that we usually >> > >>>>> use for control path? >> > >>>> >> > >>>> So both input data and output data go through single MMIO, we need to >> > >>>> introduce a protocol to pass these data, that is complex? >> > >>>> >> > >>>> And is any MMIO we can reuse (more complexer？) or we should allocate this >> > >>>> MMIO page （the old question - where to allocated?）? >> > >>> Maybe you could reuse/extend memhotplug IO interface, >> > >>> or alternatively as Michael suggested add a vendor specific PCI_Config, >> > >>> I'd suggest PM device for that (hw/acpi/[piix4.c|ihc9.c]) >> > >>> which I like even better since you won't need to care about which ports >> > >>> to allocate at all. >> > >> >> > >> Well, if Michael does not object, i will do it in the next version. :) >> > > >> > > Sorry, the thread's so long by now that I'm no longer sure what does "it" refer to. >> > >> > Never mind i saw you were busy on other loops. >> > >> > "It" means the suggestion of Igor that "map each label area right after each >> > NVDIMM's data memory" >> Michael pointed out that putting label right after each NVDIMM >> might burn up to 256GB of address space due to DIMM's alignment for 256 NVDIMMs. >> However if address for each label is picked with pc_dimm_get_free_addr() >> and label's MemoryRegion alignment is default 2MB then all labels >> would be allocated close to each other within a single 1GB range. >> >> That would burn only 1GB for 500 labels which is more than possible 256 NVDIMMs. > > I thought about it, once we support hotplug, this means that one will > have to pre-declare how much is needed so QEMU can mark the correct > memory reserved, that would be nasty. Maybe we always pre-reserve 1Gbyte. > Okay but next time we need something, do we steal another Gigabyte? > It seems too much, I'll think it over on the weekend. > > Really, most other devices manage to get by with 4K chunks just fine, I > don't see why do we are so special and need to steal gigabytes of > physically contigious phy ranges. What's the driving use case for labels in the guest? For example, NVDIMM-N devices are supported by the kernel without labels. I certainly would not want to sacrifice 1GB alignment for a label area. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
