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Date: Thu, 30 Nov 2017 17:51:17 +0100
From: Greg Kurz <groug@kaod.org>
Message-ID: <20171130175117.30b6d35a@bahia.lan>
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Subject: Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates
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To: Igor Mammedov <imammedo@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>, maxime.coquelin@redhat.com, qemu-devel@nongnu.org, mst@redhat.com

On Thu, 30 Nov 2017 16:08:44 +0100
Igor Mammedov <imammedo@redhat.com> wrote:
[...]
> > (The logic in vhost_verify_ring_mappings doesn't make sense
> > to me either though; if vhost_verify_ring_part_mapping returns 0
> > on success, why is it doing   if (!r) { break; }  surely it
> > should be  if (r) { break; })  
> it looks like a bug (CCing Greg)
> 

Wow! It's obviously a bug indeed and I'm amazed it didn't get caught
during the review :-\

I'll send a patch ASAP.

> before (f1f9e6c5 vhost: adapt vhost_verify_ring_mappings() to virtio 1 ring layout)
> logic used to be
> 
>    if changed_*_addr doesn't contain ring
>       "IGNORE as we don't care"
>    
>    if changed_*_addr contain ring AND ring can't be mapped at the same place
>       ABORT
> 
> with f1f9e6c5 we have 3 rings so on any of them following could happen
>    if "IGNORE as we don't care"
>      break => false success 
>      since it's possible that the remaining rings in vq do overlap and didn't get checked
>