[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Null scheduler and vwfi native problem

On 21/01/2021 10:54, Anders Törnqvist wrote:

Hi Anders,

Thank you for reporting the bug. I am adding Stefano and Dario as IIRC they were going to work on a solution.


I see a problem with destroy and restart of a domain. Interrupts are not available when trying to restart a domain.

The situation seems very similar to the thread "null scheduler bug" https://lists.xenproject.org/archives/html/xen-devel/2018-09/msg01213.html.

The target system is a iMX8-based ARM board and Xen is a 4.13.0 version built from https://source.codeaurora.org/external/imx/imx-xen.git.

Xen is booted with sched=null vwfi=native.
One physical CPU core is pinned to the domu.
Some interrupts are passed through to the domu.

When destroying the domain with xl destroy etc it does not complain but then when trying to restart the domain
again with a "xl create <domain cfg>" I get:
(XEN) IRQ 210 is already used by domain 1

"xl list" does not contain the domain.

Repeating the "xl create" command 5-10 times eventually starts the domain without complaining about the IRQ.

Inspired from the discussion in the thread above I have put printks in the xen/common/domain.c file. In the function domain_destroy I have a printk("End of domain_destroy function\n") in the end. In the function complete_domain_destroy have a printk("Begin of complete_domain_destroy function\n") in the beginning.

With these printouts I get at "xl destroy":
(XEN) End of domain_destroy function

So it seems like the function complete_domain_destroy is not called.

"xl create" results in:
(XEN) IRQ 210 is already used by domain 1
(XEN) End of domain_destroy function

Then repeated "xl create" looks the same until after a few tries I also get:
(XEN) Begin of complete_domain_destroy function

After that the next "xl create" creates the domain.

I have also applied the patch from https://lists.xenproject.org/archives/html/xen-devel/2018-09/msg02469.html. This does seem to change the results.

Starting the system without "sched=null vwfi=native" does not result in the problem.


Julien Grall



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.