I am trying to use the Xeon Phi card with a Xen guest VM (HVM guest) with PCI passthrough (supported by Intel's VT-d). The following is my setup:
SuperMicro SYS-1017GR-TF (has the X9SRG-F motherboard which is known to support the Phi with the latest BIOS)
Dom0: Debian Wheezy 64-bit
HVM Guest: CentOS 6.3 with stock kernel (2.6.32-279 x86_64), Xeon Phi is passed through with the Xen pciback driver
In this configuration, the VM will not boot. I'm assuming it has something to do with the special BIOS requirements that the Phi card has for memory addressing, though I'm not sure how that translates to a Xen VM.
Any thoughts or advice are greatly appreciated.