Public bug reported:

[SRU Justification]

[Impact]
A soft lockup is happening to Azure cloud customers due to a bug in netvsc_poll.

Ubuntu 4.15.0-1103 has CONFIG_NET_POLL_CONTROLLER=y in kernel config
file, there is a bug in netvsc that may cause CPU lockup with
POLL_CONTROLLER. This bug has been fixed by the following patch:

commit 2a7f8c3b1d3feedee3aa319ac220cbde3725b5d5 ("hv_netvsc: remove
ndo_poll_controller")

This commit is in mainline as of 4.20-rc1.

Microsoft would like to request this patch in 4.15 based Azure kernels.

[Test Plan]
Run high stress network traffic on an Azure instance.

[Where problems could occur]
There could be a decrease in performance or dropped packets due to NAPI not 
being able to keep up.

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: Incomplete

** Affects: linux (Ubuntu Bionic)
     Importance: Medium
     Assignee: Tim Gardner (timg-tpi)
         Status: In Progress


** Tags: bot-stop-nagging

** Also affects: linux (Ubuntu Bionic)
   Importance: Undecided
       Status: New

** Changed in: linux (Ubuntu Bionic)
       Status: New => In Progress

** Changed in: linux (Ubuntu Bionic)
   Importance: Undecided => Medium

** Changed in: linux (Ubuntu Bionic)
     Assignee: (unassigned) => Tim Gardner (timg-tpi)

** Tags added: bot-stop-nagging

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https://bugs.launchpad.net/bugs/1924314

Title:
  netvsc may cause CPU lockup

Status in linux package in Ubuntu:
  Incomplete
Status in linux source package in Bionic:
  In Progress

Bug description:
  [SRU Justification]

  [Impact]
  A soft lockup is happening to Azure cloud customers due to a bug in 
netvsc_poll.

  Ubuntu 4.15.0-1103 has CONFIG_NET_POLL_CONTROLLER=y in kernel config
  file, there is a bug in netvsc that may cause CPU lockup with
  POLL_CONTROLLER. This bug has been fixed by the following patch:

  commit 2a7f8c3b1d3feedee3aa319ac220cbde3725b5d5 ("hv_netvsc: remove
  ndo_poll_controller")

  This commit is in mainline as of 4.20-rc1.

  Microsoft would like to request this patch in 4.15 based Azure
  kernels.

  [Test Plan]
  Run high stress network traffic on an Azure instance.

  [Where problems could occur]
  There could be a decrease in performance or dropped packets due to NAPI not 
being able to keep up.

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