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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Fri, 09 Aug 2013 20:20:59 +1000
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Subject: Re: [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI
 device's DMA address space
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>, Anthony Liguori <aliguori@us.ibm.com>, "Michael S . Tsirkin" <mst@redhat.com>, qemu-devel@nongnu.org, David Gibson <david@gibson.dropbear.id.au>

On Fri, 2013-08-09 at 11:40 +0200, Paolo Bonzini wrote:
> (BTW, do you need to enable bus-master DMA on PCI bridges, to do DMA
> for devices sitting on the secondary bus?)

In theory yes though I have seen bridges who ignore it...

Cheers,
Ben.