On Tue, Jun 11, 2013 at 8:26 PM, Vijayendra Bhamidipati <vijayendra.bhamidip...@citrix.com> wrote:
> -----Original Message----- > From: David Nalley [mailto:da...@gnsa.us] > Sent: Tuesday, June 11, 2013 5:08 AM > To: dev@cloudstack.apache.org > Cc: Ryousei Takano > Subject: Re: PCI-Passthrough with CloudStack > > [Vijay>] Any specific reasons for not tracking the type of device? Different > hypervisors may implement passthrough differently. KVM may use the PCI ID but > afaik vmware does not and so we probably will need to know the type of device > in order to map it as a passthrough device. I don't think that there is any use to tracking the type of device, and a PCI device can be any kind of device. I don't have any direct experience with VMWare, but VMWare documentation (http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1010789) does show that it is recorded using the PCI ID. > [Vijay>] What is the reason for this limitation? Is it that PCI IDs can > change among PCI devices on a host across reboots? In general, what is the > effect of a host reboot on PCI IDs? Could the PCI ID of the physical device > change? Is there a way to configure passthrough devices without using the PCI > ID of the device? The limitation is to simplify the initial implementation of allocation. I believe that a PCI ID is constant (unless of course, the PCI card is physically moved inside the server). A PCI ID will always have to be specified somewhere, whether it is in the management or agent. > This looks like a compelling idea, though I am sure not limited to just > networking (think GPU passthrough). > How are things like live migration affected? Are you making planner changes > to deal with the limiting factor of a single PCI-passthrough VM being > available per host? So far, I've made the change to FirstFitAllocator so that it only assigns one VM with PCI Passthrough to one host. I'm looking to making it smarter though. (Like what Edison Su suggested) > What's the level of effort to extend this to work with VMware DirectPath I/O > and PCI passthrough on XenServer? I don't have much experience with VMware or XenServer, so I am not sure. I am actually doing this as an internship project, so my scope is likely limited to KVM. > [Vijay>] It's probably a good idea to limit the passthrough to networking to > begin with and implement other types of devices (HBA/CD-ROMs etc) > incrementally. Live migration will definitely be affected. In vmware, live > migration is disabled for a VM once the VM is configured with a passthrough > device. The implementation should handle this. A host of other features also > get disabled when passthrough is configured, and if cloudstack is using any > of those, we should handle those paths as well. With KVM, libvirt prevents live migration for machines with PCI Passthrough enabled. The errors goes back up the stack and the UI "correctly" displays the error message "Failed to migrate vm". > > Regards, > Vijay > --David Best Regards, Pawit
