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 <a...@ozlabs.ru> > > 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! -- Alexey -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
