linux - Memory Bandwidth Monitoring regression

Bug #1648088 reported by Tim Gardner
This bug affects 1 person
Affects Status Importance Assigned to Milestone
linux (Ubuntu)
Tim Gardner

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 <email address hidden>
Date: Mon Feb 22 22:19:15 2016 +0000

    x86/topology: Create logical package id


    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 <email address hidden>
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:


Revision history for this message
Tim Gardner (timg-tpi) wrote :
Changed in linux (Ubuntu Xenial):
assignee: nobody → Tim Gardner (timg-tpi)
status: New → In Progress
Changed in linux (Ubuntu):
status: New → Fix Released
Luis Henriques (henrix)
Changed in linux (Ubuntu Xenial):
status: In Progress → Fix Committed
Revision history for this message
Adam Conrad (adconrad) wrote : Update Released

The verification of the Stable Release Update for linux-aws has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

Luis Henriques (henrix)
Changed in linux (Ubuntu Xenial):
status: Fix Committed → Fix Released
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