group.of.nepali.translators team mailing list archive

[Luis Henriques <luis.henriques@xxxxxxxxxxxxx>]

** Changed in: linux (Ubuntu Xenial)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1648088

Title:
  linux - Memory Bandwidth Monitoring regression

Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Xenial:
  Fix Released

Bug description:
  Hi team,,

  I have a customer, who tried to install Xenial or upgrade to 4.4 kernel with Trusty on our cloud platform(qemu 1.5.3), reports a defect. he complains that only  one cpu is successfully detected, other cpus is disabled if
  he used 4.4 kernel. I tried to bisect Xenial kernel tree, and found that this bug was introduced by the following commit.

  commit 31c2013e4ea2e594522980acc3d20e88664b19f1
  Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
  Date:   Mon Feb 22 22:19:15 2016 +0000

      x86/topology: Create logical package id

      BugLink: http://bugs.launchpad.net/bugs/1397880

      For per package oriented services we must be able to rely on the number of CPU
      packages to be within bounds. Create a tracking facility, which

      - calculates the number of possible packages depending on
  nr_cpu_ids after boot

      - makes sure that the package id is within the number of possible packages. If
        the apic id is outside we map it to a logical package id if there is enough
        space available.

      Provide interfaces for drivers to query the mapping and do translations from
      physcial to logical ids.

  and then I backported 7b0501b1e7cddd32b265178e32d332bdfbb532d4 from
  Linus tree to Xenial kernel, the issue goes away, so could we consider
  to backport it to xenial kernel tree to solve this issue in next
  release?

  From 7b0501b1e7cddd32b265178e32d332bdfbb532d4 Mon Sep 17 00:00:00 2001
  From: Jiri Olsa <jolsa@xxxxxxxxxx>
  Date: Mon, 15 Aug 2016 12:17:00 +0200
  Subject: [PATCH] x86/smp: Fix __max_logical_packages value setup

  Frank reported kernel panic when he disabled several cores in BIOS
  via following option:

  Thanks
  Wei

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