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

[Paolo Bonzini <pbonzini@redhat.com>]

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?

>> 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