Re: [libvirt] [PATCH 0/12] Standardized device addressing & SCSI controller/disk hotplug
Hi Dan,
Looks great overall
On Thu, 2009-12-10 at 22:22 +0000, Daniel P. Berrange wrote:
I then remembered that for support NIC/VirtIO/hostdev disk unplug
Mark M had previously added PCI address information to the internal
XML state files for <interface>, <disk> and <hostdev> elements.
Note, the devaddr property in the state file only had domain/bus/slot
since there was no multi-function devices involved.
Also, we should try to handle translating the devaddr state to <address>
config - e.g. if you upgrade libvirt while a guest is running with a
hotplugged device
libvirt itself will auto-assign all drive addresses, and QEMU
will auto-assign PCI adresses in dynamic mode. When starting
a guest VM we run 'info pci' to get a list of PCI vendor/product
IDs and matching PCI addresses. We then attempt to match those
up with the devices we specified to QEMU. It sounds nasty, but
it actually works fairly well. This means we also now make it
possible to hotunplug any device, even those the VM was initially
booted with
Glad to hear this works well
There is one small issue with all this, we need to know every
PCI device in the guest. It turns out there are a handful of
devices in QEMU we don't represent in XML yet
- Virtio balloon device
- Virtio console (this is easy to address with matt's patches)
- ISA bridge
- USB controller
- Some kind of PCI bridge (not clear what this is, it has
PCI ID 8086:7113
If an management application is to be able to fully control
static PCI addressing, we need to represent these somehow,
so apps can give them addresses. Technically we could get
away with not representing the ISA/PCI bridge since QEMU
always gives them the first PCI slot no matter what. Still
need the VirtIO & USB devices dealt with.
When we discussed this on qemu-devel, we thought it made sense to only
expose "free slots" information to the higher levels - i.e. all the
management app cares about is what slots are available for address
allocation, not what is in the used slots. It also means the management
apps doesn't need to know e.g. how many PCI slots there are per bus.
Cheers,
Mark.