On Tue, 2013-07-23 at 19:07 +1000, Alexey Kardashevskiy wrote: > On 07/23/2013 12:23 PM, Alex Williamson wrote: > > On Tue, 2013-07-16 at 10:53 +1000, Alexey Kardashevskiy wrote: > >> VFIO is designed to be used via ioctls on file descriptors > >> returned by VFIO. > >> > >> However in some situations support for an external user is required. > >> The first user is KVM on PPC64 (SPAPR TCE protocol) which is going to > >> use the existing VFIO groups for exclusive access in real/virtual mode > >> on a host to avoid passing map/unmap requests to the user space which > >> would made things pretty slow. > >> > >> The protocol includes: > >> > >> 1. do normal VFIO init operation: > >> - opening a new container; > >> - attaching group(s) to it; > >> - setting an IOMMU driver for a container. > >> When IOMMU is set for a container, all groups in it are > >> considered ready to use by an external user. > >> > >> 2. User space passes a group fd to an external user. > >> The external user calls vfio_group_get_external_user() > >> to verify that: > >> - the group is initialized; > >> - IOMMU is set for it. > >> If both checks passed, vfio_group_get_external_user() > >> increments the container user counter to prevent > >> the VFIO group from disposal before KVM exits. > >> > >> 3. The external user calls vfio_external_user_iommu_id() > >> to know an IOMMU ID. PPC64 KVM uses it to link logical bus > >> number (LIOBN) with IOMMU ID. > >> > >> 4. When the external KVM finishes, it calls > >> vfio_group_put_external_user() to release the VFIO group. > >> This call decrements the container user counter. > >> Everything gets released. > >> > >> The "vfio: Limit group opens" patch is also required for the consistency. > >> > >> Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx> > > > > This looks fine to me. Is the plan to add this through the ppc tree > > again? Thanks, > > > Nope, better to add this through your tree. And faster for sure :) Thanks! Applied to my next branch for v3.12. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
