[Hyper-V] Read TSC frequency from a synthetic MSR

Bug #1715489 reported by Joshua R. Poulson on 2017-09-06
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
linux (Ubuntu)
Medium
Marcelo Cerri
Xenial
Medium
Marcelo Cerri
linux-azure (Ubuntu)
High
Marcelo Cerri
Xenial
High
Marcelo Cerri

Bug Description

It was found that SMI_TRESHOLD of 50000 is not enough for Hyper-V
guests in nested environment and falling back to counting jiffies
is not an option for Gen2 guests as they don't have PIT. As Hyper-V
provides TSC frequency in a synthetic MSR we can just use this information
instead of doing a error prone calibration.

Upstream commit here: https://github.com/torvalds/linux/commit/71c2a2d0a81f096a2932fccb39a500116fece554

Joshua R. Poulson (jrp) on 2017-09-06
Changed in linux (Ubuntu):
status: New → Confirmed
Changed in linux (Ubuntu):
importance: Undecided → Medium
tags: added: kernel-da-key kernel-hyper-v
Marcelo Cerri (mhcerri) on 2017-09-06
Changed in linux (Ubuntu):
assignee: nobody → Marcelo Cerri (mhcerri)
Marcelo Cerri (mhcerri) on 2017-09-07
Changed in linux (Ubuntu):
status: Confirmed → In Progress
status: In Progress → Confirmed
Changed in linux-azure (Ubuntu):
status: New → In Progress
importance: Undecided → High
assignee: nobody → Marcelo Cerri (mhcerri)
Marcelo Cerri (mhcerri) wrote :
Changed in linux-azure (Ubuntu Xenial):
status: New → In Progress
Changed in linux (Ubuntu Xenial):
status: New → Confirmed
importance: Undecided → Medium
Changed in linux-azure (Ubuntu Xenial):
importance: Undecided → High
Changed in linux (Ubuntu Xenial):
assignee: nobody → Marcelo Cerri (mhcerri)
Changed in linux-azure (Ubuntu Xenial):
assignee: nobody → Marcelo Cerri (mhcerri)
Marcelo Cerri (mhcerri) on 2017-09-07
Changed in linux-azure (Ubuntu):
status: In Progress → Fix Committed
Changed in linux-azure (Ubuntu Xenial):
status: In Progress → Fix Committed
Launchpad Janitor (janitor) wrote :

This bug was fixed in the package linux-azure - 4.11.0-1009.9

---------------
linux-azure (4.11.0-1009.9) xenial; urgency=low

  * linux-azure: 4.11.0-1009.9 -proposed tracker (LP: #1715731)

  * [Hyper-V] Read TSC frequency from a synthetic MSR (LP: #1715489)
    - x86/hyperv: Check frequency MSRs presence according to the specification
    - x86/hyperv: Read TSC frequency from a synthetic MSR

  * [Hyper-V] linux-azure: rdma_ucm should autoload on HPC images (LP: #1712915)
    - azure: force rdma_ucm to be loaded when hv_network_direct_* is loaded

 -- Marcelo Henrique Cerri <email address hidden> Thu, 07 Sep 2017 16:28:39 -0300

Changed in linux-azure (Ubuntu Xenial):
status: Fix Committed → Fix Released
Marcelo Cerri (mhcerri) on 2019-02-06
Changed in linux (Ubuntu):
status: Confirmed → Won't Fix
Changed in linux (Ubuntu Xenial):
status: Confirmed → Won't Fix
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