The pause is happening in the code that inits the APIC.
Its after the APIC is set up when it is beginning to init the x2APIC.
It is timing related, and when I add a lot of print statements to the
code, the problem goes away. So, its been fun trying to narrow it down.
I have it narrowed down somewhat now. I tested with the oracular:linux
6.11 kernel, and it still has the pause. I tested the jammy:aws-6.5
kernel, and it seems to run fine.
Rather than debugging the 6.8 kernel, which is very time consuming, I
will do the following in parallel:
1) I will try to do a bisect between the 6.5 and 6.8 kernels to find the
regression point
2) I will examine the commits between 6.5 and 6.8 that touched the APIC code,
and see if any stand out to be the root cause.
One of these should get the answer.
** Changed in: linux-aws (Ubuntu)
Importance: Undecided => High
** Changed in: linux-aws (Ubuntu)
Status: New => In Progress
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https://bugs.launchpad.net/bugs/2076217
Title:
booting an 24.10 or 24.04 ec2 instance with SEV-SNP enabled hangs
sometimes
Status in cloud-images:
New
Status in linux-aws package in Ubuntu:
In Progress
Bug description:
I'm trying to test an EC2 instance with SEV-SNP enabled. But the boot
process hangs at:
[snipped]
[ 0.609079] printk: legacy console [ttyS0] enabled
[ 5.405931] ACPI: Core revision 20230628
[ 5.430448] clocksource: hpet: mask: 0xffffffff max_cycles: 0xffffffff,
max_idle_ns: 30580167144 ns
[ 5.473066] APIC: Switch to symmetric I/O mode setup
Steps to reproduce are:
$ AWS_DEFAULT_REGION=eu-west-1 aws ec2 run-instances --image-id
ami-005a44922e2ffd1fa --instance-type m6a.large --cpu-options
AmdSevSnp=enabled --key-name toabctl --tag-specifications
'ResourceType=instance,Tags=[{Key=Name,Value=toabctl-2410-sevsnp-
testing}]'
The AMI ami-005a44922e2ffd1fa is ubuntu/images-testing/hvm-ssd-
gp3/ubuntu-oracular-daily-amd64-server-20240716 and does contain
6.8.0-1008-aws .
Attached is the full output from the EC2 serial console.
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