From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jan Kiszka <jan.kiszka@siemens.com>
Subject: Re: [PATCH v4 0/4] virtio: Clean up scatterlists and use the DMA API
Date: Wed, 29 Jul 2015 10:07:36 +0200
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To: Benjamin Herrenschmidt <benh@kernel.crashing.org>, Andy Lutomirski <luto@amacapital.net>
Cc: "linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, "Michael S. Tsirkin" <mst@redhat.com>, xen-devel <Xen-devel@lists.xen.org>, Christian Borntraeger <borntraeger@de.ibm.com>, Paolo Bonzini <pbonzini@redhat.com>, "linux390@de.ibm.com" <linux390@de.ibm.com>, Linux Virtualization <virtualization@lists.linux-foundation.org>
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On 2015-07-29 01:21, Benjamin Herrenschmidt wrote:
> On Tue, 2015-07-28 at 15:43 -0700, Andy Lutomirski wrote:
>>   New QEMU
>> always advertises this feature flag.  If iommu=on, QEMU's virtio
>> devices refuse to work unless the driver acknowledges the flag.
> 
> This should be configurable.

Advertisement of that flag must be configurable, or we won't be able to
run older guests anymore which don't know it, thus will reject it. The
only precondition: there must be no IOMMU if we turn it off.

Jan

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