Re: [PATCH v3 2/7] iommu/dma-iommu: Split iommu_dma_map_msi_msg() in two parts

Joerg Roedel
2019-05-03T14:04:53Z

On Wed, May 01, 2019 at 02:58:19PM +0100, Julien Grall wrote:
> On RT, iommu_dma_map_msi_msg() may be called from non-preemptible
> context. This will lead to a splat with CONFIG_DEBUG_ATOMIC_SLEEP as
> the function is using spin_lock (they can sleep on RT).
>
> iommu_dma_map_msi_msg() is used to map the MSI page in the IOMMU PT
> and update the MSI message with the IOVA.
>
> Only the part to lookup for the MSI page requires to be called in
> preemptible context. As the MSI page cannot change over the lifecycle
> of the MSI interrupt, the lookup can be cached and re-used later on.
>
> iomma_dma_map_msi_msg() is now split in two functions:
> - iommu_dma_prepare_msi(): This function will prepare the mapping
> in the IOMMU and store the cookie in the structure msi_desc. This
> function should be called in preemptible context.
> - iommu_dma_compose_msi_msg(): This function will update the MSI
> message with the IOVA when the device is behind an IOMMU.
>
> Signed-off-by: Julien Grall <julien.grall@arm.com>
> Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> Reviewed-by: Eric Auguer <eric.auger@redhat.com>

Acked-by: Joerg Roedel <jroedel@suse.de>