Bug 11363 - Support building and deploying multiple kernels for a single image
Summary: Support building and deploying multiple kernels for a single image
Status: RESOLVED FIXED
Alias: None
Product: OE-Core
Classification: Build System, Metadata & Runtime
Component: kernel (show other bugs)
Version: unspecified
Hardware: x86 Multiple
: Medium+ enhancement
Target Milestone: 2.5 M2
Assignee: Haris Okanovic
QA Contact:
URL:
Whiteboard: LET
: 3732 (view as bug list)
Depends on:
Blocks: 12320
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Reported: 2017-04-13 22:17 UTC by California Sullivan
Modified: 2018-01-17 18:30 UTC (History)
9 users (show)

See Also:
OS type for building Yocto: ---
Type of Regression: ---
Verified:
Documentation change: Yes (doc changes required)

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Description California Sullivan 2017-04-13 22:17:26 UTC 
Currently an image we create will only ever have one kernel in it. It should be possible to have a 4.9 and 4.10 kernel in the same image, for example. Ideally, we would have boot targets set up using each kernel automatically as well.
Comment 1 Tim Orling 2017-07-24 19:52:34 UTC 
If it can be designed to build from a list of kernels (we might want up to 4 different kernels in one image) that would be even better.
Comment 2 Saul Wold 2017-10-23 23:57:51 UTC 
*** Bug 3732 has been marked as a duplicate of this bug. ***
Comment 3 Robert Berger 2017-11-03 17:06:00 UTC 
The question is, do we really want different kernel versions, like 4.9, 4.10,... or would it be OK to have different patches and configs. Best would be to have a different sets of kernel version/kernel config/patches per "kernel".

Could kernel patches/configs be handled by yocto ktypes? 

I would be extremely happy with those kernels:

1) 4.9.x configured as a standard/release kernel[1]

2) 4.9.x configured as a debug kernel[2]

3) 4.9.47 preemp-rt patched/configured

4) 4.9.51 xenomai patched/configured

At the moment I create one rootfs/kernel with Yocto and the other 3 with a Yocto SDK, add user space xenomai and just exchange kernel/device trees to perform some tests.

[1] https://github.com/RobertBerger/meta-mainline/blob/rocko-training-v4.9.x/multi-v7-ml/recipes-kernel/linux/config/multi-v7-ml-base/ktypes/standard/standard.scc

[2] https://github.com/RobertBerger/meta-mainline/blob/rocko-training-v4.9.x/multi-v7-ml/recipes-kernel/linux/config/multi-v7-ml-base/ktypes/debug/debug.scc
Comment 4 Tim Orling 2017-11-08 03:23:50 UTC 
The first part of support for this has been occurring in a thread on oe-core mailing list. The latest installment is:

http://lists.openembedded.org/pipermail/openembedded-core/2017-November/144031.html

Please test this approach and give feedback. I performed a simple qemux86 build with the following in my local.conf:

PREFERRED_PROVIDER_virtual/kernel = "linux-yocto"
KERNEL_PACKAGE_NAME_pn-linux-yocto-rt = "rt-linux"
KERNEL_PACKAGE_NAME_pn-linux-yocto-tiny = "tiny-linux"
CORE_IMAGE_EXTRA_INSTALL = "rt-linux tiny-linux"

The resulting bzImages were in /boot as expected:
bzImage -> bzImage-4.12.12-yocto-standard
bzImage-4.12.12-yocto-preempt-rt
bzImage-4.12.12-yocto-tiny
Comment 5 Saul Wold 2017-12-11 00:50:07 UTC 
Assigning to actual implementor!
Comment 6 Haris Okanovic 2018-01-17 18:30:17 UTC 
Resolved by commit 6c8c8998 in openembedded-core:master