Re: [Qemu-devel] KVM call agenda for 2014-04-15

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On 04/15/2014 04:00 PM, Markus Armbruster wrote:
Juan Quintela <quintela@xxxxxxxxxx> writes:

Juan Quintela <quintela@xxxxxxxxxx> wrote:
Hi

Please, send any topic that you are interested in covering.

Thanks, Juan.
As there are no topics, no call.
Did we have a call anyway?  IRC log looks like we did...

Yes, we did. Whoever attended, please reply with things I mixed up or forgot.

Two topics:

1) pSeries IOMMU bus

Live migration registers the name for a migration blob in register_savevm_live() through qdev bus enumeration. The IOMMUs in our pSeries machine don't live on any bus, so they all get the same name. That leads to problems when we change the order of -device arguments on the command line.

One proposed solution to this is to create a bus for IOMMUs which allows us to give each IOMMU a unique name; patch is on the list.

Another proposed solution is to give devices the chance to override their name themselves. IOMMUs do know their system wide unique ID and can easily generate a unique device name for themselves. If we keep names the way they were without this callback, we can stay backwards compatible for x86 and have our IOMMUs return unique names.


2) -device for non-PCI devices

There are 2 reasons we want to create "platform" devices using -device on the command line. One is that Xilinx is trying to create a full machine from the command line. The other one is that we want VFIO for platform devices.

a) IRQs

The "Anthony" way of doing IRQ links between random devices is his stateful Pin object approach. Since Anthony is gone and it'd be a lot of refactoring, we don't deem this approach realistic.

Andreas suggested that we could make every qemu_irq a QOM object that then gets a global name in the QOM hierarchy and can be addressed as connector for IRQ output lines of devices in the -device command line syntax.

b) Memory Regions

The "Anthony" approach was to turn memory regions into QOM objects. That allows to expose memory region links as QOM links.

The currently proposed approach is to add a -sysbusdev (or -device) command line option that hard codedly puts memory region n of device x into address a of the physical address space.

c) Device Granularity

We talked about the granularity of VFIO platform devices per -device option. I was advocating that we should have a -device granularity that "makes sense" for the user, rather than individual separate components. The main reason for that is that we lose information about links of different components of a device when we make it separate devices.


Alex

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