Re: [Xen-devel] [PATCH V13 4/7] xen/arm: Data abort exception (R/W) mem_events.

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Thu, 2015-03-12 at 16:19 +0100, Tamas K Lengyel wrote:
> 
> >  out:
>                 > +    if ( flush )
>                 > +    {
>                 > +        flush_tlb_domain(d);
>                 > +        iommu_iotlb_flush(d, sgfn, egfn - sgfn);
>                 > +    }
>                 
>                 Is moving the flush out of the loop an independent bug
>                 fix? If so please
>                 do in a separate commit with a rationale in the commit
>                 log. If it is
>                 somehow related to the changes here then please
>                 mention it in this
>                 commit log, since it's a bit subtle.
>         
>         
>         Right, it's not a bugfix and not required to be outside the
>         loop, I think I just moved it because it made sense to me to
>         flush it only once instead at every iteration. I'll place it
>         back.

> 
> Sorry, the flush wasn't actually part of the loop to begin with. I
> just moved it under the label out so that the TLB gets flushed when
> the memaccess setting hypercall gets preempted. I will just set a
> separate label for it before out so that the existing behavior is
> preserved but the tlb is still flushed when memaccess is preempted.

I wonder why this isn't needed for the other uses of goto out, i.e. on
the relinquish check.

I'm not convinced this isn't just a straight up bug. Anyone remember any
reasoning why we don't flush on exit if any work has been done?

Ian.



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