[Bug 1976399] [NEW] focal/azure: The console log of ARM64 Ubuntu 18.04 has duplicate output

Public bug reported:

SRU Justification

[Impact]

There is duplicate output on the console . LSG team identify the root
cause and suggested to apply two patches below.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ad8cd1db80cc33337bdbee63c453ef6d5132474b
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e369d8227fd211be36242fc44a9dc2209e246b9a

What we are hitting is exactly in the second commit's log. Ubuntu kernel
also needs the following diff:

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index f07367100ece..dca15e27123a 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2203,7 +2203,7 @@ static int __init console_setup(char *str)
* for exacly this purpose.
*/
if (str[0] == 0 || strcmp(str, "null") == 0) {
- __add_preferred_console("ttynull", 0, NULL, NULL);
+ __add_preferred_console("ttynull", 0, NULL, NULL, true);
return 1;
}

Linux kernel: 5.4.0-1078-azure
Tested in Azure
Host version: 22477.1101-1-0
Image: Canonical 0002-com-ubuntu-server-arm-preview-bionic 18_04-lts 18.04.202205020

From Azure Serial Console, we can see duplicate output.

Such as:

[ 3.109140] Platform Keyring initialized
[ 3.109140] Platform Keyring initialized
[ 3.117148] Key type asymmetric registered
[ 3.117148] Key type asymmetric registered
[ 3.122303] Asymmetric key parser 'x509' registered
[ 3.122303] Asymmetric key parser 'x509' registered

[Test Plan]

Microsoft tested

[Where things could go wrong]

The kernel log could get corrupted.

[Other Info]

SF: #00338148

** Affects: linux-azure (Ubuntu)
Importance: Undecided
Status: Fix Released

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

** Package changed: linux (Ubuntu) => linux-azure (Ubuntu)

** Changed in: linux-azure (Ubuntu)
Status: New => Fix Released

** Also affects: linux-azure (Ubuntu Focal)
Importance: Undecided
Status: New

** Changed in: linux-azure (Ubuntu Focal)
Importance: Undecided => Medium

** Changed in: linux-azure (Ubuntu Focal)
Status: New => In Progress

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

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https://bugs.launchpad.net/bugs/1976399

Title:
focal/azure: The console log of ARM64 Ubuntu 18.04 has duplicate
output

Status in linux-azure package in Ubuntu:
Fix Released
Status in linux-azure source package in Focal:
In Progress

Bug description:
SRU Justification

[Impact]

There is duplicate output on the console . LSG team identify the root
cause and suggested to apply two patches below.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ad8cd1db80cc33337bdbee63c453ef6d5132474b
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e369d8227fd211be36242fc44a9dc2209e246b9a

What we are hitting is exactly in the second commit's log. Ubuntu
kernel also needs the following diff:

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index f07367100ece..dca15e27123a 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2203,7 +2203,7 @@ static int __init console_setup(char *str)
* for exacly this purpose.
*/
if (str[0] == 0 || strcmp(str, "null") == 0) {
- __add_preferred_console("ttynull", 0, NULL, NULL);
+ __add_preferred_console("ttynull", 0, NULL, NULL, true);
return 1;
}

Linux kernel: 5.4.0-1078-azure
Tested in Azure
Host version: 22477.1101-1-0
Image: Canonical 0002-com-ubuntu-server-arm-preview-bionic 18_04-lts 18.04.202205020

From Azure Serial Console, we can see duplicate output.

Such as:

[ 3.109140] Platform Keyring initialized
[ 3.109140] Platform Keyring initialized
[ 3.117148] Key type asymmetric registered
[ 3.117148] Key type asymmetric registered
[ 3.122303] Asymmetric key parser 'x509' registered
[ 3.122303] Asymmetric key parser 'x509' registered

[Test Plan]

Microsoft tested

[Where things could go wrong]

The kernel log could get corrupted.

[Other Info]

SF: #00338148

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