Re: [libvirt] [PATCH v2 01/10] Introduce NVDIMM memory model
On Thu, Sep 08, 2016 at 14:59:07 +0100, Daniel Berrange wrote:
On Thu, Sep 08, 2016 at 03:50:40PM +0200, Michal Privoznik wrote:
[...]
This is very different to how we deal with addressing for all other
types of device in libvirt, where we always assign addresses
immediately at time the guest is defined. By only assigning addresses
transiently when QEMU starts up, then you're liable to get different
addressing even if the DIMM config isn't isn't changed. eg addition
of other unrelated devices may alter the address QEMU ends up assigning
to the DIMMS. Your arguments in favour of not having persistent addresses
aren't really in any way specific to DIMMs, so if we wanted to take that
approach, then it would apply to all types of device. So I think we need
to fix DIMM address assignment so that it works exactly the same way as
we do for all other device addressing needs and assign it up front.
Well, we certainly can assign the slot numbers (I'm going to fix this
soon as it may create problems).
It's nearly impossible for us to assign the memory module base address
though. This would require to re-implement all the platform specific
code that maps memory in qemu which would be ridiculous.
I think that an attempt to do so would most certainly break if not kept
in sync with qemu. I still strongly prefer not to attempt to do this and
just discover the addresses so that we can keep them across migrations.
Peter