Chapter 1. Package Updates
138
• In previous kernels the
tuntap
device send path did not have any packet accounting. This meant
that the user-space sender could pin down arbitrary amounts of kernel memory by continuing to
send data to an end-point that was congested. This update adds packet accounting to the
tun
driver so that
virtio-net
gets congestion feedback which is necessary to prevent packet loss for
protocols lacking congestion control (such as UDP) when used in a guest. (
BZ#495863
1025
)
• This update adds the virtualization feature VT-d. This feature provides hardware support for directly
assigning physical devices to Xen fully virtualized (HVM) guests or KVM guests. The principal
benefit of the feature is to improve device access performance to be close to native speeds. Please
refer to the
Red Hat Knowledgebase
1026
before using PCI device assignment with this technology to
avoid possible system instability issues. (
BZ#500901
1027
)
VT-d support is disabled by default. To enable VT-d one must add intel_iommu=on to the
kernel commandline. Enabling VT-d is required to assign a host's PCI device to a KVM guest.
(BZ#504363)
1028
Additionally, only the assignment of NIC devices from host to guest is supported. Assigning a
block device (hard disk) to a guest is not supported. On hardware platforms that support IOMMU
passthrough it is recommended to also use the
iommu=pt
kernel commandline option as this will
improve the performance of I/O devices in the host. This parameter has no effect on performance
for devices assigned to guests.
When the iommu=pt mode, if a device is assigned to (and then de-assigned from) a guest, it can no
longer be used in the host until the host has been rebooted. PCI hotplug devices can not be used in
iommu=pt mode
• This update includes a fix for kernel panic encountered when attempting to run a
kdump
process on
hardware virtual machine (HVM) in an ia64 architecture environment. (
BZ#418591
1029
)
• This update corrects softlockup issues encountered when booting earlier kernel versions in a virtual
environment and setting the clocksource to read from the system's Programmable Interval Timer
(PIT). (
BZ#427588
1030
)
• A problem identified with Xen kernels manifested with
meminfo
reporting an incorrect
LowTotal
of 4Tb. A patch applied to the driver alters how
highmem
pages are handled and corrects the error.
(
BZ#428892
1031
)
• When users set
LPFC HBA
storage to reset in a loop the system would attempt to rediscover
SCSI
devices and some of these processes would time-out. The issue was found to be code paths
deleting
SCSI
devices without setting the device state to
SDEV_DEL
. A patch included in this update
corrects this behavior(
BZ#430170
1032
)
• The Xen kernel does not currently support the suspend functionality. A fix has been applied to this
release to remove the "Suspend" option from graphical user interface menus. (
BZ#430928
1033
)
• This update fixes a race condition when queuing incoming
iucv
messages by spreading
the message queue spinlock in the
message_pending
callback across the entire callback
function.This resolves the race condition and enhances system stability. (
BZ#499626
1034
)
• This feature fixes
hexdump
data in
s390dbf
traces, allowing Red Hat Enterprise Linux to have
complete registered state change notification (RSCN) traces (up to 1024 bytes). (
BZ#470618
1035
)
Summary of Contents for ENTERPRISE 5.4 RELEASE NOTES
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