Von:   Paolo Bonzini <pbonz...@redhat.com> 


> > Yes, it's ugly but it's legal.  It probably doesn't happen on real hardware 
> > that computes the checksum after or during DMA and has some kind of buffer 
> > inside the board.  But on virt there is only one copy until we reach the 
> > actual physical hardware. 
>  
> okay, so it's no bug. and there is no way to detect that the page is dirty 
> (again). so i need a bounce buffer if i have data checksums? 
 
I think so, yes. 


It turned out that for writes a bounce buffer is indeed always necessary. But 
what I found out is that
it seems that even for reads it happens that the OS (Windows in this case) 
issues 2 read requests with
the same buffer in parallel. Is it possible that this is a bug in the virtio or 
has anybone ever seen this before?


Thanks,
Peter


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