[Xen-users] Correct Syntax for VCPU-Pinning

[Florian Heigl <florian.heigl@xxxxxxxxx>]

Hi all,

today I have wanted to do hard vcpu pinning from the domU config file
and found life still does *all* it can to stay challenging.

Take a VM with 2 vcpus that should be hard-pinned to two physical CPUs.
We'll use one core and one HT for this experiment.

One might try the following config.
vcpus = 2
cpus = [ "1", "5" ]

But this is in fact wrong. As we can see from xm vcpu-list this will
define two vcpus which are both runnable on cpu 1 or 5.

myvm                           29     0     5   r--      16.2 1,5
myvm                           29     1     5   ---      13.9 1,5

Whereas a
xm vcpu-pin myvm 0 1
xm vcpu-pin myvm 0 5

in fact does the right thing

myvm                           29     0     1   -b-      20.5 1
myvm                           29     1     5   -b-      18.6 5

in xm list --long this is presented as following format:
    (cpus (1 5))
And that entry doesn't change when I do the hard pinning.

So, is this in fact impossble to specify from a domU config file?

Greetings,
Florian

-- 
the purpose of libvirt is to provide an abstraction layer hiding all
xen features added since 2006 until they were finally understood and
copied by the kvm devs.

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