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Re: [Xen-devel] [PATCH v4 0/4] virtio: Clean up scatterlists and use the DMA API
- To: Paolo Bonzini <pbonzini@xxxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxxxxxx>, Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
- From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
- Date: Wed, 29 Jul 2015 10:20:34 +0200
- Cc: "linux-s390@xxxxxxxxxxxxxxx" <linux-s390@xxxxxxxxxxxxxxx>, "Michael S. Tsirkin" <mst@xxxxxxxxxx>, Stefan Hajnoczi <stefanha@xxxxxxxxx>, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, xen-devel <Xen-devel@xxxxxxxxxxxxx>, Christian Borntraeger <borntraeger@xxxxxxxxxx>, Cornelia Huck <cornelia.huck@xxxxxxxxxx>, "linux390@xxxxxxxxxx" <linux390@xxxxxxxxxx>, Linux Virtualization <virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Wed, 29 Jul 2015 08:21:03 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
On 2015-07-29 10:17, Paolo Bonzini wrote:
>
>
> On 29/07/2015 02:47, Andy Lutomirski wrote:
>>>> If new kernels ignore the IOMMU for devices that don't set the flag
>>>> and there are physical devices that already exist and don't set the
>>>> flag, then those devices won't work reliably on most modern
>>>> non-virtual platforms, PPC included.
>>>
>>> Are there many virtio physical devices out there ? We are talking about
>>> a virtio flag right ? Or have you been considering something else ?
>>
>> Yes, virtio flag. I dislike having a virtio flag at all, but so far
>> no one has come up with any better ideas. If there was a reliable,
>> cross-platform mechanism for per-device PCI bus properties, I'd be all
>> for using that instead.
>
> No, a virtio flag doesn't make sense.
That will create the risk of subtly breaking old guests over new setups.
I wouldn't suggest this.
Jan
--
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux
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