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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 08/08/2016 21:35, Alina wrote:
> 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.

unlikely($X) is an optimisation, which causes the compiler to reorder
the jumps to avoid branch misprediction penalties, based on the
programmers assertion of which case is more likely.

>
> Does anyone have any idea why the hypervisor does not see them as being
> equal?

They are equal, and that is the problem.

I presume you are trying to enable logdirty mode (you haven't specified
which shadow_control you are trying to enable), but it is not permitted
for a domain to make such adjustments to itself.

~Andrew

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