Fix extended topology enumeration leaf #7087
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
When booting a Linux guest in SMP configuration, the following kernel warning can be observed: [Firmware Bug]: CPUID leaf 0xb subleaf 1 APIC ID mismatch 1 != 0 The reason is that we announce the presence of the extended topology leaf, but fail to announce the x2apic ID in EDX. Signed-off-by: Thomas Prescher <[email protected]> On-behalf-of: SAP [email protected]
phip1611
approved these changes
May 21, 2025
Contributor
|
(@tpressure, yes yes, sandpile is not super reliable. :-D) |
Member
Author
I actually looked into the x2apic specification and, although difficult to read, i think this is what belongs into EDX. I also checked the Linux source code which basically just confirms that the APIC IDs from different sources are identical. |
rbradford
approved these changes
May 21, 2025
russell-islam
approved these changes
May 21, 2025
Merged
via the queue into
cloud-hypervisor:main
with commit May 22, 2025
d172a5d
39 of 40 checks passed
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
6 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
When booting a Linux guest in SMP configuration, the following kernel warning can be observed:
[Firmware Bug]: CPUID leaf 0xb subleaf 1 APIC ID mismatch 1 != 0The reason is that we announce the presence of the extended topology leaf, but fail to announce the x2apic ID in EDX.
I found this issue because I am currently working on x86_64 support for >255 vCPUs where this fix is absolutely needed in order to convince Linux to boot the additional processors above 255.