Re: [Xen-devel] "Tried to do a paging op on itself"

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

Hello,

> When I try to enable shadow page table features using the shadow_control
> function, I get this message in the hypervisor logs: "Tried to do a paging
> op on itself". After backtracking to the source of this message, I
> discovered it comes from the condition: "if ( unlikely(d == current->domain)
> )", which means that the hypervisor does not consider the current domain as
> the same domain I give as parameter, even though I checked and their
> domain_id is the same.
> 
> Does anyone have any idea why the hypervisor does not see them as being
> equal?

On the contrary, that's exactly how the hypervisor sees them (as the
message states: "paging op _on_itself_").

You're probably mistakenly thinking of the "unlikely()" as some sort of
NOT, but that's not the case. Unlikely() is merely being used for
optimization purposes (so the statements says that the developer thinks
that d will be equal to current->domain very rarely).


Cheers,
Razvan


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