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Bug 452587

Summary: [BUGFIX] CPU hotplug support for x86_64
Product: Red Hat Enterprise Linux 5 Reporter: Alok Kataria <akataria>
Component: kernelAssignee: Prarit Bhargava <prarit>
Status: CLOSED NOTABUG QA Contact: Martin Jenner <mjenner>
Severity: low Docs Contact:
Priority: low    
Version: 5.2CC: peterm, sborman, srihan
Target Milestone: rcKeywords: Reopened
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2008-07-01 19:29:58 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Attachments:
Description Flags
Support physical cpu hotplug for x86_64
none
Fix paranoia about using BIOS quickboot mechanism.
none
fix "buggy BIOS check" when CPUs are hot removed none

Description Alok Kataria 2008-06-23 22:04:00 UTC 
Description of problem:

Physical hotplug support for x86_64 kernels is broken in RHEL 5.2
RHEL 5.2 kernel is missing some code in ACPI to support physical hot remove of
CPUs. Even though there is a eject object under sysfs, because of the missing
support the CPU cannot be physically hot-removed. 
Along with this there are couple of bug's which are triggered when CPU are
hot-removed and added back to the system. 


Version-Release number of selected component (if applicable):
RHEL 5.2

Attached are patches which help physical cpu hotplug on rhel 5.2 (2.6.18-92).
All of these are backport of patches from the mainline tree. The patch headers
have information regarding the original commit.

Info about patches : 
1. acpi-hotplug-support.patch : Implements acpi_map_lsapic() and
acpi_unmap_lsapic() to support physical cpu hotplug.
2. bios_quickboot-mechanism : Fix paranoia about using BIOS quickboot mechanism
3. buggy-bios-check.patch : fix "buggy BIOS check" when CPUs are hot removed

Please apply. 

Thanks,
Alok
Comment 1 Alok Kataria 2008-06-23 22:04:00 UTC 
Created attachment 310080 [details]
Support physical cpu hotplug for x86_64
Comment 2 Alok Kataria 2008-06-23 22:05:41 UTC 
Created attachment 310081 [details]
Fix paranoia about using BIOS quickboot mechanism.
Comment 3 Alok Kataria 2008-06-23 22:06:18 UTC 
Created attachment 310082 [details]
fix "buggy BIOS check" when CPUs are hot removed
Comment 5 Prarit Bhargava 2008-06-27 12:07:45 UTC 
Please be advised, that Bugzilla is not a support tool. It is an
Engineering and Community tool. So although all changes to Enterprise
Linux go through Bugzilla and Red Hat considers issues directly entered
into Bugzilla valuable feedback, there is no SLA around it.

If this is a production issue, please report it to your Red Hat Support contact.

Thank you.
Comment 6 Alok Kataria 2008-07-01 18:57:05 UTC 
(In reply to comment #5)
> Please be advised, that Bugzilla is not a support tool. It is an
> Engineering and Community tool. So although all changes to Enterprise
> Linux go through Bugzilla and Red Hat considers issues directly entered
> into Bugzilla valuable feedback, there is no SLA around it.
> 

Hi Prarit,

This is a BUG in the current RHEL 5.2 kernel code. The code for physical ACPI
CPU-hotplug is missing in 2.6.18 and subsequently from the RHEL kernel.  It was
merged in the mainline tree in the 2.6.19 release cycle. This bug can be hit on
a native system too which supports physical CPU hot plug. 

I had already backported the patches so attached them with the report. 

Similarly the other two patches too fixes BUGS while hotplug and were accepted
in the mainline tree.  These bugs can be hit with logical hotplug as well, i.e.
while offline-online'ing a cpu.

Here is the commit info for the individual patches, please cherry pick these
patches for the RH kernels. 

1. ACPI hotplug support
73fea175303926055440c06bc8894f0c5c58afc8

2. BIOS quickboot
63d38198a0f57dca87e6cb79931c7bedbb7ab069

3. Buggy bios check
ba62b077871a5255e271f4fdae57167651839277

Thanks you,
Alok

> If this is a production issue, please report it to your Red Hat Support contact.
> 
> Thank you.
>
Comment 7 Prarit Bhargava 2008-07-01 19:29:58 UTC 
Hi Alok,

RHEL5 does not support CPU hotswap.  We do support CPU hotplug, but not physical
additions and removals.

Thanks,

P.