Re: [PATCH v2 14/24] iommu: Introduce explicit type for non-strict DMA domains

Jean-Philippe Brucker
2021-07-30T09:25:44Z

On Wed, Jul 28, 2021 at 04:58:35PM +0100, Robin Murphy wrote:
> Promote the difference between strict and non-strict DMA domains from an
> internal detail to a distinct domain feature and type, to pave the road
> for exposing it through the sysfs default domain interface.
>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>

Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>

> ---
> drivers/iommu/dma-iommu.c | 2 +-
> drivers/iommu/iommu.c | 8 ++++++--
> include/linux/iommu.h | 11 +++++++++++
> 3 files changed, 18 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index e28396cea6eb..8b3545c01077 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -1311,7 +1311,7 @@ void iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 dma_limit)
> * The IOMMU core code allocates the default DMA domain, which the
> * underlying IOMMU driver needs to support via the dma-iommu layer.
> */
> - if (domain->type == IOMMU_DOMAIN_DMA) {
> + if (iommu_is_dma_domain(domain)) {
> if (iommu_dma_init_domain(domain, dma_base, dma_limit, dev))
> goto out_err;
> dev->dma_ops = &iommu_dma_ops;
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index fa8109369f74..982545234cf3 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -115,6 +115,7 @@ static const char *iommu_domain_type_str(unsigned int t)
> case IOMMU_DOMAIN_UNMANAGED:
> return "Unmanaged";
> case IOMMU_DOMAIN_DMA:
> + case IOMMU_DOMAIN_DMA_FQ:
> return "Translated";
> default:
> return "Unknown";
> @@ -552,6 +553,9 @@ static ssize_t iommu_group_show_type(struct iommu_group *group,
> case IOMMU_DOMAIN_DMA:
> type = "DMA\n";
> break;
> + case IOMMU_DOMAIN_DMA_FQ:
> + type = "DMA-FQ\n";
> + break;
> }
> }
> mutex_unlock(&group->mutex);
> @@ -765,7 +769,7 @@ static int iommu_create_device_direct_mappings(struct iommu_group *group,
> unsigned long pg_size;
> int ret = 0;
>
> - if (!domain || domain->type != IOMMU_DOMAIN_DMA)
> + if (!domain || !iommu_is_dma_domain(domain))
> return 0;
>
> BUG_ON(!domain->pgsize_bitmap);
> @@ -1947,7 +1951,7 @@ static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
> /* Assume all sizes by default; the driver may override this later */
> domain->pgsize_bitmap = bus->iommu_ops->pgsize_bitmap;
>
> - if (type == IOMMU_DOMAIN_DMA && iommu_get_dma_cookie(domain)) {
> + if (iommu_is_dma_domain(domain) && iommu_get_dma_cookie(domain)) {
> iommu_domain_free(domain);
> domain = NULL;
> }
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 141779d76035..046ba4d54cd2 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -61,6 +61,7 @@ struct iommu_domain_geometry {
> #define __IOMMU_DOMAIN_DMA_API (1U << 1) /* Domain for use in DMA-API
> implementation */
> #define __IOMMU_DOMAIN_PT (1U << 2) /* Domain is identity mapped */
> +#define __IOMMU_DOMAIN_DMA_FQ (1U << 3) /* DMA-API uses flush queue */
>
> /*
> * This are the possible domain-types
> @@ -73,12 +74,17 @@ struct iommu_domain_geometry {
> * IOMMU_DOMAIN_DMA - Internally used for DMA-API implementations.
> * This flag allows IOMMU drivers to implement
> * certain optimizations for these domains
> + * IOMMU_DOMAIN_DMA_FQ - As above, but definitely using batched TLB
> + * invalidation.
> */
> #define IOMMU_DOMAIN_BLOCKED (0U)
> #define IOMMU_DOMAIN_IDENTITY (__IOMMU_DOMAIN_PT)
> #define IOMMU_DOMAIN_UNMANAGED (__IOMMU_DOMAIN_PAGING)
> #define IOMMU_DOMAIN_DMA (__IOMMU_DOMAIN_PAGING | \
> __IOMMU_DOMAIN_DMA_API)
> +#define IOMMU_DOMAIN_DMA_FQ (__IOMMU_DOMAIN_PAGING | \
> + __IOMMU_DOMAIN_DMA_API | \
> + __IOMMU_DOMAIN_DMA_FQ)
>
> struct iommu_domain {
> unsigned type;
> @@ -90,6 +96,11 @@ struct iommu_domain {
> struct iommu_dma_cookie *iova_cookie;
> };
>
> +static inline bool iommu_is_dma_domain(struct iommu_domain *domain)
> +{
> + return domain->type & __IOMMU_DOMAIN_DMA_API;
> +}
> +
> enum iommu_cap {
> IOMMU_CAP_CACHE_COHERENCY, /* IOMMU can enforce cache coherent DMA
> transactions */
> --
> 2.25.1
>
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