Re: [Xen-devel] "CPU N still not dead..." messages during microcode update stage of boot when smt=0

[Juergen Gross <jgross@xxxxxxxx>]

On 02.08.19 04:15, Andy Smith wrote:
> Hi,
>
> On Mon, Jul 22, 2019 at 01:06:03PM +0100, Andrew Cooper wrote:
> > On 22/07/2019 10:16, Jan Beulich wrote:
> > > On 21.07.2019 22:06, Andy Smith wrote:
> > > > (XEN) Adding cpu 1 to runqueue 0
> > > > (XEN) CPU 1 still not dead...
> > > > (XEN) CPU 1 still not dead...
> > > > (XEN) CPU 1 still not dead...
> > > > (XEN) CPU 1 still not dead...
> […]
>
> > Does reverting back to credit1 make the issue go away?
> Yes, I don't see this with sched=credit, smt=0 and SMT enabled in
> the BIOS:
>
> (XEN) microcode: CPU2 updated from revision 0x2000057 to 0x200005e, date = 
> 2019-04-02
> (XEN) microcode: CPU4 updated from revision 0x2000057 to 0x200005e, date = 
> 2019-04-02
> (XEN) microcode: CPU6 updated from revision 0x2000057 to 0x200005e, date = 
> 2019-04-02
> (XEN) microcode: CPU8 updated from revision 0x2000057 to 0x200005e, date = 
> 2019-04-02
> (XEN) microcode: CPU10 updated from revision 0x2000057 to 0x200005e, date = 
> 2019-04-02
> (XEN) microcode: CPU12 updated from revision 0x2000057 to 0x200005e, date = 
> 2019-04-02
> (XEN) microcode: CPU14 updated from revision 0x2000057 to 0x200005e, date = 
> 2019-04-02
> (XEN) Brought up 8 CPUs
> (XEN) Parked 8 CPUs
This will be cured by my core scheduling series. As I don't think we
want to wait for that to go in I can isolate the related patches and
post them.

The needed patches will be:

xen/sched: use one schedule lock for all free cpus
xen/sched: populate cpupool0 only after all cpus are up
xen/sched: remove cpu from pool0 before removing it
xen/sched: add minimalistic idle scheduler for free cpus

With those in place credit2 will never be in charge for a cpu just being
brought up, which in turn can't block a cpu to be parked right away.


Juergen

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel