Re: [Qemu-devel] [PATCH v8 4/4] vfio: Enable for SPAPR

[Alex Williamson <alex.williamson@redhat.com>]

On Fri, 2014-06-06 at 13:34 +1000, Alexey Kardashevskiy wrote:
> This turns the sPAPR support on and enables VFIO container use
> in the kernel.
> 
> This extends vfio_connect_container to support VFIO_SPAPR_TCE_IOMMU type
> in the host kernel.
> 
> This registers a memory listener which sPAPR IOMMU will notify when
> executing H_PUT_TCE/etc DMA calls. The listener then will notify the host
> kernel about DMA map/unmap operation via VFIO_IOMMU_MAP_DMA/
> VFIO_IOMMU_UNMAP_DMA ioctls.
> 
> This executes VFIO_IOMMU_ENABLE ioctl to make sure that the IOMMU is free
> of mappings and can be exclusively given to the user. At the moment SPAPR
> is the only platform requiring this call to be implemented.
> 
> Note that the host kernel function implementing VFIO_IOMMU_DISABLE
> is called automatically when container's fd is closed so there is
> no need to call it explicitly from QEMU. This may change in the future.

So you're saying we rely on a behavior that may change in the future...
The kernel must do cleanup, it can never rely on userspace to do the
right thing or we have a bug.  Does that mean we can remove the "may
change in the future" part of this comment or is that directed at QEMU's
behavior and not the kernel's?  A comment in the code where we setup the
release handler or call ENABLE would be a good idea too.  Thanks,

Alex

> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
> Changes:
> v8:
> * added note about VFIO_IOMMU_DISABLE in the commit log
> 
> v7:
> * added more details in commit log
> 
> v5:
> * multiple returns converted to gotos
> 
> v4:
> * fixed format string to use %m which is a glibc extension:
> "Print output of strerror(errno). No argument is required."
> ---
>  hw/misc/vfio.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
> index bb77934..78d2045 100644
> --- a/hw/misc/vfio.c
> +++ b/hw/misc/vfio.c
> @@ -3650,6 +3650,34 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
>  
>          container->iommu_data.type1.initialized = true;
>  
> +    } else if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_IOMMU)) {
> +        ret = ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &fd);
> +        if (ret) {
> +            error_report("vfio: failed to set group container: %m");
> +            ret = -errno;
> +            goto free_container_exit;
> +        }
> +
> +        ret = ioctl(fd, VFIO_SET_IOMMU, VFIO_SPAPR_TCE_IOMMU);
> +        if (ret) {
> +            error_report("vfio: failed to set iommu for container: %m");
> +            ret = -errno;
> +            goto free_container_exit;
> +        }
> +
> +        ret = ioctl(fd, VFIO_IOMMU_ENABLE);
> +        if (ret) {
> +            error_report("vfio: failed to enable container: %m");
> +            ret = -errno;
> +            goto free_container_exit;
> +        }
> +
> +        container->iommu_data.type1.listener = vfio_memory_listener;
> +        container->iommu_data.release = vfio_listener_release;
> +
> +        memory_listener_register(&container->iommu_data.type1.listener,
> +                                 container->space->as);
> +
>      } else {
>          error_report("vfio: No available IOMMU models");
>          ret = -EINVAL;