Re: [Xen-users] Slightly OT: OS Resource Question

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> In principle, can a running Linux kernel recognize the addition of new
> physical hardware resources such as CPUs, memory, or PCI devices?  Strictly
> speaking, I'm not asking just about a running Xen instance -- but about a
> standalone, booted OS.

Yes, it can - if the hardware supports it and the kernel you use has drivers 
for doing so.

The support for these things varies depending on what resource is involved.  
e.g. hotplugging memory is hard because some of the memory could contain 
kernel data structures, be pinned for IO operations, etc...

Under Xen you can hot(un)plug virtual CPUs to a virtual machine, and 
dynamically change the memory allocation (although it's not strictly hotplug, 
the effect is similar).

On x86 you can hotplug CPUs to/from the kernel (I think???) but the hardware 
doesn't actually allow them to be swapped whilst the machine is running.  On 
better hardware I believe this is possible.

HTH,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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