Red Hat Enterprise Linux 7.4 for ARM - Release Notes

Red Hat Enterprise Linux 7.4 for ARM introduces Red Hat Enterprise Linux 7.4 user space with an updated kernel. The new kernel version 4.11 is provided by the kernel-alt packages. The offering is distributed with other updated packages; most of the packages are standard Red Hat Enterprise Linux 7 Server RPMs.

Installation ISO images are available on the Customer Portal Downloads page.

For information about Red Hat Enterprise Linux 7.4 user space, see the Release Notes and other Red Hat Enterprise Linux 7 documentation.

The following packages are being distributed with this release:

• binutils
• elinks
• iproute
• js
• kernel-alt
• libproxy
• mesa-private-llvm
• mozjs17
• oprofile
• papi and libpfm
• polkit
• rdma-core
• systemtap

The following packages are provided as Development Preview in this release:

• libvirt (Optional channel)
• qemu-kvm (Optional channel)

Note: KVM is a development preview (unsupported) on the 64-bit ARM architecture. Customers may contact Red Hat and describe their use case, which will be taken into consideration for a future release of Red Hat Enterprise Linux.

Kernel Configuration Changes

HW Enablement

• Bluetooth (disabled)
• WIRELESS (disabled)
• CPU_IDLE (enabled)
• GPIO_DWAPB (enabled)
• I2C (enabled) - Designware, QUP, and XLP9XX
  • sensor support:
    • IIO drivers (disabled)
    • Accel sensors (disabled)
    • light + orientation + interrupt trigger (disabled)
• Input driver
  • mouse, synaptics, rmi4
• LED
  • Intel SS4200 (disabled)
• Generic IRQ CHIP (enabled)
• Hibernate (enabled)
• Clock Source DATA (enabled)
• Sound
  • OSS_CORE (disabled)
  • all SND drivers (disabled)

Networking Driver Support

• Thunder2 driver (enabled)
• Amazon (enabled)
• Altera (disabled)
• ARC (disabled)
• Broadcom B44, BCMGENET, BNX2X_VLAN, CNIC (disabled)
• Hisilicon (enabled)
• cadence MACB (disabled)
• Chelsio T3 (disabled)
• Intel E1000 (disabled)
• Mellanox (enabled)
• myri10GE (disabled)
• Qlogic - qla2xxx, netxen_nic, Qed, Qede (enabled)
• Qualcomm - qcom_emac (enabled)
• Broadcom - bcm7xxx (disabled)

Infiniband Support (enabled)

• CXBG4, I40IW, MLX4, MLX5, IPOIB, IPOIB_CM, IPOIB_DEBUG, ISERT, SRP, SRPT (enabled)

Core Kernel Support

• Schedule Imbalance (enabled)
• 48 bit VA support (enabled)
• tick cpu accounting (disabled)
• Context Tracking (enabled)
• RCU NOCB (enabled)
• CGROUP-Hugetlb (enabled)
• CRIU (enabled)
• BPF_SYSCALL (disabled)
• PERF_USE_VMALLOC (disabled)
• HZ_100/HZ (enabled)
• NO_HZ_IDLE (disabled)
• NO_HZ_FULL (enabled)
• BPF_EVENTS (disabled)
• LZ4 compression (disabled)
• BTREE (enabled)
• CPUMASK_OFFSTACK (disabled)
• DEBUG_INFO_DWARF4 (enabled)
• SCHEDSTATS (enabled)
• Striaght DEVMEM (disabled)
• Transparent Hugepage (HTP) (enabled)
• ZSMaLLOC_STAT, IDLE_PAGE_TRACKING(enabled)
• PAGE_EXTENSION and PAGE_POISONING (disabled)

Networking Stack support

• SLIP - (enabled)
• JME (disabled)
• IPVLAN (disabled)
• BPF_JIT (disabled)
• dccp (disabled)
• [ipv4] NET_FOU, Diag, CDG, NV (disabled)
• [ipv6] ILA (disabled), GRE (enabled)
• MAC80211 (disabled)
• netfilter _ conntrack (enabled)

Graphic/GPU Support

• DRM_I2C_SIL64 (disabled)
• TTY
  • serial_nonstandard, cyclades, synclinkmp, synclink_gt, N_HDLC, serial_8250_MID (enabled)
  • fbdev (enabled)
• USB - PHY (disabled)

Storage Support

• Block scsi request (enabled)
• Block debugfs (enabled)
• Block Multi-Queue PCI (enabled)
• Block Multi-Queue VirtIO (enabled)
• Block Multi-Queue IOSched_deadline (enabled)
• MD Long Write -(disabled)
• SCSI - ARCMSR, AM53C974, WD719x, BNX2X_FCOE, BNX2_ISCSI, ESAS2R (disabled)
• SCSI - HISI_SAS (enabled)
• SPI - QUP, SLP (enabled)
• SSB (disabled)

File Systems

• FS_DAX (enabled)
• BTRFS (disabled)
• Ceph (enabled)
• DLM (disabled)
• FSCAHE (disabled)
• GFS2 (disabled)
• Swap over NFS (disabled)
• NFS-FSCACHE (enabled)

Virtualization and KVM Support

• KVM_IRQCHIP, KVM_IRQ_ROUTING, KVM_MSI (enabled)
• Virtio - noiommu (enabled)

Known Issues

NMI watchdog reports soft lockups under heavy CPU load

A kernel bug concerning a fairness issue when CPUs are competing for the global task lock, which happens in cases where many short-lived tasks are created, may cause processes to be killed. When this happens, the kernel ring buffer (dmesg) displays error messages similar to the following:

NMI watchdog: BUG: soft lockup - CPU#47 stuck for 44s! [stress-ng-sleep:9967]

The cause of the bug is unknown at the time of writing this document, and there is no available workaround. (BZ#1454844)

ipmitool communicates with BMC only when "IPMI_SI=no" on Cavium ThunderX

When starting ipmi.service with the systemctl command, the default configuration attempts to load the ipmi_si driver. On Cavium ThunderX systems, which do not have an IPMI SI device, ipmi.service incorrectly removes the ipmi_devintf driver. Consequently, the ipmitool utility in the kernel is not able to communicate with the Baseboard Management Controller (BMC).

To work around this problem, edit the /etc/sysconfig/ipmi file and set the IPMI_SI variable as follows:

IPMI_SI=no

Then, reboot the operating system if necessary. As a result, the correct drivers are loaded and ipmitool can communicate with BMC through the /dev/ipmi0 directory. (BZ#1448181)

Bug Fixes

Memory exhaustion causing OOM on the 64-bit ARM systems has been fixed when kdump or CMA features are enabled

On the 64-bit ARM systems with memory limited to <=1G, the crash kernel consumed about 512M of memory and the Contiguous Memory Allocator (CMA) took around 512M of the remaining memory, thus exhausting the system memory. Consequently, some user-space applications, such as Shared Memory in Linux (SHM)(/dev/shm), could cause the out-of-memory (OOM) conditions with the following error message:

Out of memory: Kill process 23474 (shm_open_23-1.r) score 0 or sacrifice child

With this update, the underlying kexec source code addressing the crash kernel and CMA has been fixed. As a result, the OOM conditions due to memory exhaustion no longer occur when dumping the kernel on systems with limited memory size. (BZ#1492799)