CPUHotPlug - Revision history

Bsd: typo in category name

2015-05-31T14:11:36Z

typo in category name

← Older revision		Revision as of 10:11, 31 May 2015
Line 28:		Line 28:


	[[Category:~~Architechture~~]][[Category:Docs]]		[[Category:Architecture]][[Category:Docs]]

Bsd: added categories

2015-05-31T13:45:09Z

added categories

← Older revision		Revision as of 09:45, 31 May 2015
Line 26:		Line 26:
	* bring it online by writting 1 to the "online" file inside that directory on guest		* bring it online by writting 1 to the "online" file inside that directory on guest
	* Try adding as many cpus as possible, and make sure we at least do not crash.		* Try adding as many cpus as possible, and make sure we at least do not crash.


			[[Category:Architechture]][[Category:Docs]]

Lmr at 15:58, 25 January 2010

2010-01-25T15:58:46Z

← Older revision		Revision as of 11:58, 25 January 2010
Line 10:		Line 10:

	Hot-unplug does not work, and actually, does not even make that much sense.		Hot-unplug does not work, and actually, does not even make that much sense.

			Note: Some people might expect KVM virtualization to behave similarly to IBM power virtualization, power machines can virtualize several LPARS, and each one of the physical power processors can be split on 10 processing units, that can be assigned to machines at will. So effectively on that platform we have good support for adding and removing new CPUs to the guest systems. Perhaps that's why people request this feature. Obviously the situation under intel hardware is different.

	== Status ==		== Status ==
Line 20:		Line 22:

	* switch to the monitor		* switch to the monitor
	* type cpu_set <n+1> on		* type 'cpu_set <n+1> online'
	* A new cpu should appear on /sys/devices/system/cpu		* A new cpu should appear on /sys/devices/system/cpu
	* bring it online by writting 1 to the "online" file inside that directory		* bring it online by writting 1 to the "online" file inside that directory on guest
	* Try adding as many cpus as possible, and make sure we at least do not crash.		* Try adding as many cpus as possible, and make sure we at least do not crash.

Glommer at 13:30, 19 January 2010

2010-01-19T13:30:39Z

New page

= CPU Hotplug =

CPU hotplug is a controverse feature. It exists on qemu-kvm for
some time now, and according to some BZ movement, we know there are users for
it. There are very few physical machines that actually support it. (Only one
unisys box I know of), The Linux implementation follows what this specific
box do, but happens to break Windows SVVP tests in an appearently unsolvable
way. No one knows how to implement it on Windows, but it is believed that
it should involve a windows-specific driver (to be written)

Hot-unplug does not work, and actually, does not even make that much sense.

== Status ==

Linux guest support is pretty old, dating back to something around 2.6.19. qemu-kvm support exists, but merging it into qemu.git was not successful when tried, in the past. Reason being the BIOS changes, for the reasons already mentioned.

== Testing ==

In any case, here's how to verify it:

* switch to the monitor
* type cpu_set <n+1> on
* A new cpu should appear on /sys/devices/system/cpu
* bring it online by writting 1 to the "online" file inside that directory
* Try adding as many cpus as possible, and make sure we at least do not crash.