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Re: Null scheduler and vwfi native problem

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?




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