From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH v4 0/4] virtio: Clean up scatterlists and use the DMA API
Date: Wed, 03 Sep 2014 10:01:44 +0200
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To: Andy Lutomirski <luto@amacapital.net>
Cc: "linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>, Benjamin Herrenschmidt <benh@au1.ibm.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, "Michael S. Tsirkin" <mst@redhat.com>, Linux Virtualization <virtualization@lists.linux-foundation.org>, Christian Borntraeger <borntraeger@de.ibm.com>, "linux390@de.ibm.com" <linux390@de.ibm.com>
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Il 03/09/2014 09:52, Andy Lutomirski ha scritto:
>> > IOMMU support for x86 is going to go in this week.
>> >
> Can you try to make sure that qemu-system-x86_64 -device iommu -device
> virtio-balloon-pci (or whatever the syntax is) doesn't put the
> virtio-pci device behind the IOMMU?  Because, if it does, then the
> kernel will have to support that, and it'll be messy.

Right now it will not put the device behind the IOMMU, but I'm fairly
sure that the DMAR will show the device as being behind the IOMMU.

We have time till QEMU 2.2 is out to make it use the IOMMU for
virtio-pci devices on x86.  I'm not worried about that.

The virtio-pci devices do set the "bus master" bit in the command
register, right?  I think they do, because otherwise MSIs will not be
received by the guest.

Paolo