Re: [Xen-devel] [PATCH 2/3] xen: Have schedulers revise initial placement

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.07.16 at 20:02, <george.dunlap@xxxxxxxxxx> wrote:
> The generic domain creation logic in
> xen/common/domctl.c:default_vcpu0_location() attempts to try to do
> initial placement load-balancing by placing vcpu 0 on the least-busy
> non-primary hyperthread available.  Unfortunately, the logic can end
> up picking a pcpu that's not in the online mask.  When this is passed
> to a scheduler such which assumes that the initial assignment is
> valid, it causes a null pointer dereference looking up the runqueue.
> 
> Furthermore, this initial placement doesn't take into account hard or
> soft affinity, or any scheduler-specific knowledge (such as historic
> runqueue load, as in credit2).
> 
> To solve this, when inserting a vcpu, always call the per-scheduler
> "pick" function to revise the initial placement.  This will
> automatically take all knowledge the scheduler has into account.
> 
> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx>

Should this and patch 3 be backported?

Jan


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