Re: [PATCH qemu-kvm] device assignment: default requires IOMMU

[Alexander Graf <agraf@suse.de>]

Chris Wright wrote:
> [ resend, fixing email header, sorry for duplicate ]
>
> The default mode for device assignment is to rely on an IOMMU for
> proper translations and a functioning device in the guest.  The current
> logic makes this requirement advisory, and simply disables the request
> for IOMMU if one is not found on the host.  This makes for a confused
> user when the device assignment appears to work, but the device in the
> guest is not functioning  (I've seen about a half-dozen reports with
> this failure mode).
>
> Change the logic such that the default requires the IOMMU.  Period.
> If the host does not have an IOMMU, device assignment will fail.
>
> This is a user visible change, however I think the current situation is
> simply broken.
>
> And, of course, disabling the IOMMU requirement using the old:
>
>    -pcidevice host=[addr],dma=none
>
> or the newer:
>
>    -device pci-assign,host=[addr],iommu=0
>
> will do what it always did (not require an IOMMU, and fail to work
> properly).
>   

Avi,

could you please cherry-pick this into 0.12-stable?
I don't feel too eager getting 500 bug reports from people who try out
device passthrough with disabled or no IOMMU.

Alex