问题描述

现场NF5466M5主机，产线预装操作系统RHEL6.7，软件包使用全包安装的方式，现场实施发现USB设备无法使用，并且有接入USB设备后宕机的情况。收集日志发现有如下报错。

Sep 22 11:02:48 localhost pulseaudio[7275]: pid.c: Stale PID file, overwriting.

Sep 22 11:05:39 localhost kernel: usb 1-2: new low speed USB device number 4 using xhci_hcd

Sep 22 11:05:39 localhost kernel: usb 1-2: device descriptor read/64, error -71

Sep 22 11:05:39 localhost kernel: xhci_hcd 0000:00:14.0: Setup ERROR: setup context command for slot 3.

Sep 22 11:05:39 localhost kernel: hub 1-0:1.0: unable to enumerate USB device on port 2

Sep 22 11:05:41 localhost kernel: dmar: DRHD: handling fault status reg 2

Sep 22 11:05:41 localhost kernel: dmar: DMAR:[DMA Read] Request device [00:14.0] fault addr 0

Sep 22 11:05:41 localhost kernel: DMAR:[fault reason 06] PTE Read access is not set

Sep 22 11:05:47 localhost kernel: xhci_hcd 0000:00:14.0: Timeout while waiting for a slot

Sep 22 11:05:56 localhost kernel: xhci_hcd 0000:00:14.0: Stopped the command ring failed, maybe the host is dead

Sep 22 11:05:56 localhost kernel: xhci_hcd 0000:00:14.0: Abort command ring failed

Sep 22 11:05:56 localhost kernel: xhci_hcd 0000:00:14.0: HC died; cleaning up

Sep 22 11:05:56 localhost kernel: hub 1-0:1.0: cannot reset port 2 (err = -19)

Sep 22 11:05:56 localhost kernel: hub 1-0:1.0: cannot disable port 2 (err = -19)

涉及范围

M5/M4机型+搭配rhel6.x+全包安装操作系统。grub.conf及menu.lst有iommu=on的字样。

处理方案

重启后在菜单选择的时候按e修改参数，将intel_iommu=on amd_iommu=on中的on改成off，进入系统之后再修改grub.conf文件，修改内容与前面一致。

故障根因

sosreport中看到/proc/cmdline中有intel_iommu=on amd_iommu=on参数。

根据以往的经验，在一些机器上使用intel_iommu时偶尔会在插拔USB设备时出现系统hang住的问题；

在低版本内核中，还存在启动intel_iommu后kdump服务无法收集vmcore的问题，这些问题都和RHEL6版本的内核中相关的实现有关。