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Re: [Qemu-devel] RFC: vfio API changes needed for powerpc


From: Scott Wood
Subject: Re: [Qemu-devel] RFC: vfio API changes needed for powerpc
Date: Wed, 3 Apr 2013 13:39:43 -0500

On 04/03/2013 01:32:26 PM, Stuart Yoder wrote:
On Tue, Apr 2, 2013 at 5:50 PM, Scott Wood <address@hidden> wrote:
> On 04/02/2013 04:38:45 PM, Alex Williamson wrote:
>>
>> On Tue, 2013-04-02 at 16:08 -0500, Stuart Yoder wrote:
>> >     VFIO_IOMMU_MAP_MSI(iova, size)
>
>
> Not sure how you mean "size" to be used -- for MPIC it would be 4K per bank, > and you can only map one bank at a time (which bank you're mapping should be > a parameter, if only so that the kernel doesn't have to keep iteration state
> for you).

The intent was for user space to tell the kernel which windows to use
for MSI. So I envisioned a total size of window-size * msi-bank-count.

Size doesn't tell the kernel *which* banks to use, only how many. If it already knows which banks are used by the group, then it also knows how many are used. And size is misleading because the mapping is not generally going to be contiguous.

-Scott



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