From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:45040)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <anshul.makkar@profitbricks.com>) id 1X857g-0006bL-AU
	for qemu-devel@nongnu.org; Fri, 18 Jul 2014 06:10:44 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <anshul.makkar@profitbricks.com>) id 1X857b-000816-QB
	for qemu-devel@nongnu.org; Fri, 18 Jul 2014 06:10:40 -0400
Received: from mail-qa0-f41.google.com ([209.85.216.41]:58025)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <anshul.makkar@profitbricks.com>) id 1X857b-000810-Ci
	for qemu-devel@nongnu.org; Fri, 18 Jul 2014 06:10:35 -0400
Received: by mail-qa0-f41.google.com with SMTP id j7so2900717qaq.0
	for <qemu-devel@nongnu.org>; Fri, 18 Jul 2014 03:10:34 -0700 (PDT)
MIME-Version: 1.0
In-Reply-To: <CAM4NYE8KGrQ0TCa1w986cvE-e=F2Gq-PVq=j3oUmVVUWSNfyxg@mail.gmail.com>
References: <CAM4NYE8KGrQ0TCa1w986cvE-e=F2Gq-PVq=j3oUmVVUWSNfyxg@mail.gmail.com>
From: Anshul Makkar <anshul.makkar@profitbricks.com>
Date: Fri, 18 Jul 2014 12:10:14 +0200
Message-ID: <CAM4NYE-NX-E49MW8sxesg3cm-uLUEYEMePYwU5EFsqWNkMxdLw@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Subject: Re: [Qemu-devel] virtio + virtq + iommu
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: qemu-devel <qemu-devel@nongnu.org>

Further adding on to it.

 iotlb = mr->iommu_ops->translate(mr, addr) in address_space_translate
to get the translation from the tlb.

What I found is that the  "iommu_ops->translate" is assigned a
function pointer only for alpha/typhoon and ppc/spapr. What about x86.
Are we using any of these architectures for emulating
iommu for x86 ?

Anshul Makkar

On Tue, Jul 8, 2014 at 5:21 PM, Anshul Makkar
<anshul.makkar@profitbricks.com> wrote:
> Hi,
>
> Was tracing the buffer handling code flow after the kick has been
> initiated from the guest in case of virtio.
>
> Found this function
> cpu_physical_memory_map->address_space_map->address_space_translate
> which calls address_space_translate_internal and iommu->translate (get
> the translation from TLB) to get the corresponding host virtual
> address where I think the packet buffer is mapped to (from guest
> physical to host virtual).
>
> So, should I conclude that there is no hardware IOMMU involved in this
> translation. QEMU maintains its own TLB and translation mapping which
> is used. Or iommu->translate leads to hardware MMU call.
>
> We are developing a high speed packet transfer mechanism using
> infiniband cards. So, trying to analyse every possible bottleneck.
>
> Confused here, please suggest.
>
> Anshul Makkar
> www.justkernel.com