Hi, We've been successfully using Xen with PCI pass-through of disk and network cards for a couple of years now. We have this architecture working successfully with a wide range of hardware from HP and Dell but recently have been getting problems with the HP ProLiant DL380p Gen8 and its P420i RAID controller. When we bind the RAID controller to pciback and issue the appropriate 'xl pci-attach' command the controller appears on the driver domain but fails during probing by the hpsa driver. Interestingly, in about 1 in every 10 test runs the hpsa driver probes successfully, the controller appears in the driver domain and the disks appear to function correctly. In the failure cases the syslog output from the hpsa driver is as follows: Jul 7 13:30:01 zylevel0-HVM-domU kernel: [ 54.855597] bus: 'pci': driver_prob e_device: matched device 0000:00:00.0 with driver hpsa Jul 7 13:30:01 zylevel0-HVM-domU kernel: [ 54.855599] bus: 'pci': really_prob e: probing driver hpsa with device 0000:00:00.0 Jul 7 13:30:01 zylevel0-HVM-domU kernel: [ 54.855605] HP HPSA Driver (v 3.4.4 -1) Jul 7 13:30:01 zylevel0-HVM-domU kernel: [ 54.855684] hpsa 0000:00:00.0: enab ling device (0000 -> 0003) Jul 7 13:30:01 zylevel0-HVM-domU kernel: [ 54.855983] hpsa 0000:00:00.0: Xen PCI mapped GSI34 to IRQ29 Jul 7 13:30:01 zylevel0-HVM-domU kernel: [ 54.856089] hpsa 0000:00:00.0: enab ling bus mastering Jul 7 13:30:01 zylevel0-HVM-domU kernel: [ 54.856659] hpsa 0000:00:00.0: MSIX Jul 7 13:30:01 zylevel0-HVM-domU kernel: [ 54.857384] hpsa 0000:00:00.0: Logi cal aborts not supported Jul 7 13:40:00 zylevel0-HVM-domU kernel: [ 654.318297] hpsa 0000:00:00.0: unable to get board into simple mode Jul 7 13:40:00 zylevel0-HVM-domU kernel: [ 654.318478] hpsa: probe of 0000:00:00.0 rejects match -19 The error seems to originate from the hpsa_enter_simple_mode function and looks like the first point where an interaction with the board via IO mapped memory is expected to result in a response from the board. We are using Xen 4.4 and a newly built Linux 3.15.0 kernel with Ubuntu trusty. VTd is disabled in the BIOS of the Dom-0. We use the following Grub commands for the Dom-0 boot: multiboot /boot/xen.gz placeholder dom0_mem=max:2048m iommu=0 loglvl=all guest_loglvl=all module /boot/vmlinuz-3.15.0 placeholder root=UUID=f56cf02b-d46f-4e2a-b667-242f97ec82f5 ro debug module --nounzip /boot/initrd.img-3.15.0 The driver domain is a PV guest running the same kernel version as the Dom-0. The Xen configuration file contains the following kernel boot parameters: extra="earlyprintk=xen debug max_loop=64 iommu=soft" After we issue the pci-attach command the following additional lines appear in the 'xl dmesg' log: (XEN) grant_table.c:289:d0 Increased maptrack size to 2 frames (XEN) mm.c:809: d2: Forcing read-only access to MFN f7f02 (XEN) mm.c:809: d0: Forcing read-only access to MFN f7f02 We were wondering whether anyone in the community had got PCI pass-through of the P420i working, or any pointers of where to look to further diagnose the problem. Best wishes, Simon