Re: [PATCH v1 15/22] Add iommufd configure option

[Jason Gunthorpe]

On Wed, Sep 20, 2023 at 07:37:53PM +0200, Eric Auger wrote:

> >> qemu will typically not be able to
> >> self-open /dev/iommufd as it is root-only.
> >
> > I don't understand, we open multiple fds to KVM devices. This is the
> > same.
> Actually qemu opens the /dev/iommu in case no fd is passed along with
> the iommufd object. This is done in
> [PATCH v1 16/22] backends/iommufd: Introduce the iommufd object, in
> 
> iommufd_backend_connect(). I don't understand either.

The char dev node is root only so this automatic behvaior is fine
but not useful if qmeu is running in a sandbox.

I'm not sure what "multiple fds to KVM devices" means, I don't know
anything about kvm devices..

The iommufd design requires one open of the /dev/iommu to be shared
across all the vfios.

Jason