Re: Null scheduler and vwfi native problem

[Anders Törnqvist <anders.tornqvist@xxxxxxxxx>]

On 1/22/21 3:26 PM, Julien Grall wrote:
> Hi Anders,
>
> On 22/01/2021 08:06, Anders Törnqvist wrote:
> > On 1/22/21 12:35 AM, Dario Faggioli wrote:
> > > On Thu, 2021-01-21 at 19:40 +0000, Julien Grall wrote:
> > - booting with "sched=null vwfi=native" but not doing the IRQ 
> > passthrough that you mentioned above
> > "xl destroy" gives
> > (XEN) End of domain_destroy function
> >
> > Then a "xl create" says nothing but the domain has not started 
> > correct. "xl list" look like this for the domain:
> > mydomu                                   2   512     1 ------       0.0
> This is odd. I would have expected ``xl create`` to fail if something 
> went wrong with the domain creation.
> The list of dash, suggests that the domain is:
>    - Not running
>    - Not blocked (i.e cannot run)
>    - Not paused
>    - Not shutdown
>
> So this suggest the NULL scheduler didn't schedule the vCPU. Would it 
> be possible to describe your setup:
>   - How many pCPUs?
There are 6 pCPUs
>   - How many vCPUs did you give to dom0?
I gave it 5
>   - What was the number of the vCPUs given to the previous guest?
Nr 0.

Listing vcpus looks like this when the domain is running:

xl vcpu-list
Name                                ID  VCPU   CPU State   Time(s) 
Affinity (Hard / Soft)
Domain-0                             0     0    0   r--     101.7 0 / all
Domain-0                             0     1    1   r--     101.0 1 / all
Domain-0                             0     2    2   r--     101.0 2 / all
Domain-0                             0     3    3   r--     100.9 3 / all
Domain-0                             0     4    4   r--     100.9 4 / all
mydomu                              1     0    5   r--      89.5 5 / all

vCPU nr 0 is also for dom0. Is that normal?

> One possibility is the NULL scheduler doesn't release the pCPUs until 
> the domain is fully destroyed. So if there is no pCPU free, it 
> wouldn't be able to schedule the new domain.
> However, I would have expected the NULL scheduler to refuse the domain 
> to create if there is no pCPU available.
> @Dario, @Stefano, do you know when the NULL scheduler decides to 
> allocate the pCPU?
> Cheers,