Kernel-Xen - Red Hat ENTERPRISE LINUX 5.4 - TECHNICAL NOTES Manual

Chapter 4. Known Issues
To work around this limitation, booting or installation can be done using the default behavior. After
the iscsi and iscsid services start, the iscsi service can log into the target using iSCSI iface binding.
This however, will leave an extra session using the default behavior, and it has to be manually
logged out using the following command:
iscsiadm -m node -T target -p ip -I default -u
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4.12. kernel-xen

• When booting paravirtualized guests that support gigabyte page tables (i.e. a Fedora 11 guest) on
Red Hat Enterprise Linux 5.4 Xen, the domain may fail to start if more than 2047MB of memory
is configured for the domain. To work around this issue, pass the "nogbpages" parameter on the
guest kernel command-line.
• Boot parameters are required to enable SR/IOV Virtual Function devices. SR/IOV Virtual Function
devices can only be accessed if the parameter pci_pt_e820_access=on is added to the boot stanza
in the /boot/grub/grub.conf file. For example:
title Red Hat Enterprise Linux Server (2.6.18-152.el5xen)
root (hd0,1)
kernel /xen.gz-2.6.18-152.el5 com1=115200,8n1 console=com1 iommu=1
module /vmlinuz-2.6.18-152.el5xen ro root=LABEL=/ console=ttyS0,115200
pci_pt_e820_access=on
This enables the MMCONF access method for the PCI configuration space, a requirement for VF
device support
• When using Single Root I/O Virtualization (SR-IOV) devices under Xen, a single Hardware Virtual
Machine (HVM) guest is limited to 12 Virtual Function (VF) assignments.
• When booting a fully virtualized Xen guest, the following message may be displayed on the guest
console:
testing NMI watchdog ... <4>
WARNING: CPU#0: NMI appears to be stuck (0->0)!
This issue is caused by an implementation issue with the Xen hypervisor and can be safely ignored.
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• Diskette drive media will not be accessible when using the virtualized kernel. To work around this,
use a USB-attached diskette drive instead.
Note that diskette drive media works well with other non-virtualized kernels.
• Formatting a disk when running Windows 2008 or Windows Vista as a guest can crash when the
guest has been booted with multiple virtual CPUs. To work around this, boot the guest with a single
virtual CPU when formatting.
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