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Re: Null scheduler and vwfi native problem

Hi Dario,

On 30/01/2021 17:59, Dario Faggioli wrote:
On Fri, 2021-01-29 at 09:08 +0100, Anders Törnqvist wrote:
On 1/26/21 11:31 PM, Dario Faggioli wrote:
Thanks again for letting us see these logs.

Thanks for the attention to this :-)

Any ideas for how to solve it?

So, you're up for testing patches, right?

How about applying these two, and letting me know what happens? :-D

They are on top of current staging. I can try to rebase on something
else, if it's easier for you to test.

Besides being attached, they're also available here:


I could not test them properly on ARM, as I don't have an ARM system
handy, so everything is possible really... just let me know.

It should at least build fine, AFAICT from here:


Julien, back in:


you said I should hook in enter_hypervisor_head(),
leave_hypervisor_tail(). Those functions are gone now and looking at
how the code changed, this is where I figured I should put the calls
(see the second patch). But feel free to educate me otherwise.

enter_hypervisor_from_guest() and leave_hypervisor_to_guest() are the new functions.

I have had a quick look at your place. The RCU call in leave_hypervisor_to_guest() needs to be placed just after the last call to check_for_pcpu_work().

Otherwise, you may be preempted and keep the RCU quiet.

The placement in enter_hypervisor_from_guest() doesn't matter too much, although I would consider to call it as a late as possible.


Julien Grall



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