Re: [Qemu-devel] [PATCH 5/7] memory: Allow replay of IOMMU mapping notifications

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Sep 28, 2015 at 10:59:03AM +0200, Paolo Bonzini wrote:
> 
> 
> On 26/09/2015 08:54, David Gibson wrote:
> > On Fri, Sep 25, 2015 at 02:04:14PM +0200, Paolo Bonzini wrote:
> >> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256
> >> 
> >> 
> >> 
> >> On 25/09/2015 13:33, David Gibson wrote:
> >>> 1) Is there a case where using the no-replay functions makes 
> >>> sense?
> >>> 
> >>> I'm not sure.  I think vfio is the only user so far, so I
> >>> guess that's technically a no.  I was reluctant to change the
> >>> interface and semantics just off the bat, though.
> >> 
> >> Considering memory_region_listener does the reply, I think it's 
> >> okay.
> > 
> > Uh.. just to be clear, are you saying I should change this so
> > there's only the replaying interface?
> 
> Maybe...  The only issue is the "granularity" argument, which is
> not in memory_region_register_iommu_notifier.  That makes me wonder if
> the replay and registration make sense as separate operations.
> 
> What about adding a new function memory_region_iommu_replay and
> separate the two phases?

Hm.. I'm not sure I see much advantage to separating the phases.  But
I don't particularly object to the idea either.  So, I think it's your
call.

> >> For solving the problem that Laurent mentioned, using int128
> >> seems like the easiest solution...
> > 
> > Maybe.  It means I have to do all the address calculation in the
> > loop with an int128, then truncate it to do the actual call.  That
> > seems harder to me than the overflow check I added, but I suppose
> > it's conceptually similar in some ways.
> 
> Your overflow check is also okay, I wrote this before seeing the
> updated version.
> 
> Paolo
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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