Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and allocation APIs

David Gibson
2021-05-13T06:07:22Z

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On Wed, May 05, 2021 at 01:39:02PM -0300, Jason Gunthorpe wrote:
> On Wed, May 05, 2021 at 02:28:53PM +1000, Alexey Kardashevskiy wrote:
>
> > This is a good feature in general when let's say there is a linux supported
> > device which has a proprietary device firmware update tool which only exists
> > as an x86 binary and your hardware is not x86 - running qemu + vfio in full
> > emulation would provide a way to run the tool to update a physical device.
>
> That specific use case doesn't really need a vIOMMU though, does it?

Possibly not, but the mechanics needed to do vIOMMU on different host
IOMMU aren't really different from what you need for a no-vIOMMU
guest. With a vIOMMU you need to map guest IOVA space into the host
IOVA space. With no no-vIOMMU you need to map guest physical
addresses into the host IOVA space. In either case the GPA/gIOVA to
userspace and userspace to HPA mappings are basically arbitrary.

--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson

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