Re: [Xen-users] Hotplugging FPGA to running VM

[Anil Rao <anil.rao@xxxxxxxxxxxx>]

Yes, the guest OS has PCI hotplug support. I am able to hotplug a variety of PCI devices to the VM. The only one that doesn't work is the FPGA device. Even for this one, the only time it doesn't work, is if the VM was powered-on prior to the FPGA device being brought on-line on the host. If the FPGA was present before the VM was powered-on everything works as expected.

 

It somehow seems like new devices that are introduced in the host, after a VM has been started on it, cannot be hotplugged into the VM.

 

Thanks.

-Anil

 

 

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From: theubaz@xxxxxxxxx [mailto:theubaz@xxxxxxxxx] On Behalf Of John Sherwood
Sent: Wednesday, May 30, 2012 7:20 PM
To: Anil Rao
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Hotplugging FPGA to running VM

Are you sure the guest OS has PCI hotplug support?

On Wed, May 30, 2012 at 10:14 PM, Anil Rao <anil.rao@xxxxxxxxxxxx> wrote:

Hi,

 

I am trying to assign a FPGA (which is a PCI device) to a running VM. The interesting thing here is that the FPGA is not present when the VM was powered-on. I.e. sometime after the VM was started, the FPGA was brought on-line on the host by downloading its image to the device.

 

So far my attempts at using Xen PCI-passthrough have not been successful. Although Xen reports that the pass-through operation was successful, which I have verified using the appropriate xl command, I am unable to see the FPGA from within the guest OS.

 

I have tried both manual rescanning of the PCI bus inside the guest as well as making use of the pciehp driver. The only way I can (reliably) see the FPGA from within the guest, is to shutdown and restart the VM and then redo the hotplug operation. I want to avoid a VM reboot and was wondering if this is at all possible and if so what do I need to do to realize it.

 

[The virtualization host is based on the default Xen setup that comes with SLES 11 SP2]

 

Thanks for any help on this matter.

 

-Anil

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