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It appears that CentOS 7 cannot work with paravirtualized drivers with XenServer 6.2

I’ve installed one PVHVM guest with the xs-tools package but the drivers fails to connect at bootime.

I got this message on the dmesg, on the DomU:

[    0.000000] Xen Platform: blacklisted by host

When I would expect to receive those ones:

[    0.000000] Netfront and the Xen platform PCI driver have been compiled for this kernel: unplug emulated NICs.
[    0.000000] Blkfront and the Xen platform PCI driver have been compiled for this kernel: unplug emulated disks.

And in the Dom0 in got the corresponding messages:

Jul 11 15:39:03 xenserver1 fe: qemu-dm-53[2380]: UNPLUG: protocol version set to 1 (drivers not blacklisted)
Jul 11 15:39:03 xenserver1 fe: qemu-dm-53[2380]: UNPLUG: protocol 1 active
Jul 11 15:39:03 xenserver1 fe: qemu-dm-53[2380]: UNPLUG: product_id: 3 build_number: 1
Jul 11 15:39:03 xenserver1 fe: qemu-dm-53[2380]: UNPLUG: drivers blacklisted
Jul 11 15:39:04 xenserver1 fe: qemu-dm-53[2380]: vga s->lfb_addr = f1000000 s->lfb_end = f1800000 

Due this problem I’m stuck using the emulated Realtek Fast Ethernet driver, and I would like to know it's something possible to workarround this problem or even a real solution.

XenServer 6.2 is getting really dated today, and I'm afraid that there are under the hood incompatibilities that will not enable CentOS 7 in its glory using XenServer 6.2.

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2 Answers 2

Try installing CentOS 7 in fully-paravirtualized mode. You can use a kickstart to automate the installation; so long as the grub configuration files are patched to be readable by XenServer 6.2's pygrub, the virtual machine will boot. XenServer Tools will install properly inside the paravirtual machine.

The next version is due soon, and you may have better luck when it's released.

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PVHVM guests performs faster than fully PV guests, that's why we are doing it this way, and using PV mode we lose the netinstall feature that we really need. To achive a PVHVM guest, just install it as HVM and then load it up with xs-tools. The kernel will be aware of the HVM mode and turn on necessary features to be in PVHVM mode. Anyway I'll take a look at your tip, but this not really solves the problem. Thanks! – Vinícius Ferrão Jul 17 '14 at 17:32
I've been able to get PVHVM guests to work, too, on XenServer Creedence Alpha 4. It's possible you'll need to wait til the next release for CentOS 7 to be fully supported under PVHVM. – Frederick Aug 7 '14 at 7:34

I've installed CentOS 7.0 and Oracle Linux 7.0 as domU in XenServer 6.2 SP1 with latest hotfixes. No problem at all. I've used the Install DVD ISO though.

Make sure you choose "Other Media" when installing using the DVD. The stock kernel 3.10 certainly has the xen guest support (pvops) and will detect the xen hypervisor, unplug the emulated NICs and Disks use the PV drivers.

Looks like the error message was originated from arch/x86/xen/platform-pci-unplug.c

switch (protocol) {
    case 1:
            printk(KERN_ERR "Xen Platform: blacklisted by host\n");
            return XEN_PLATFORM_ERR_BLACKLIST;
        printk(KERN_WARNING "Xen Platform PCI: unknown I/O protocol version");

I know XenServer 6.1 has a hotfix for this issue but for 6.2 SP1 with latest hotfix, it should not be affected. Make sure you patch it up to the latest XS62ESP1008.

PV will probably NOT work because the PV templates are not yet available.

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