[PATCH v3 5/6] iommu: Introduce __IOMMU_DOMAIN_LP

[Sven Peter]

__IOMMU_DOMAIN_LP (large pages) indicates that a domain can handle
conditions where PAGE_SIZE might be smaller than the IOMMU page size.
Always allow attaching trusted devices to such domains and set the flag for
IOMMU_DOMAIN_DMA, which can now handle these situations.

Note that untrusted devices are not yet supported. Those require
additional changes to allow aligning swiotlb buffers to granularities
larger than PAGE_SIZE.

Signed-off-by: Sven Peter <sven@xxxxxxxxxxxxx>
---
 drivers/iommu/iommu.c |  9 +++++++--
 include/linux/iommu.h | 13 +++++++++++--
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 28896739964b..66bba6a6bb28 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1976,10 +1976,15 @@ void iommu_domain_free(struct iommu_domain *domain)
 }
 EXPORT_SYMBOL_GPL(iommu_domain_free);
 
-static int iommu_check_page_size(struct iommu_domain *domain)
+static int iommu_check_page_size(struct iommu_domain *domain,
+				struct device *dev)
 {
+	bool trusted = !(dev_is_pci(dev) && to_pci_dev(dev)->untrusted);
+
 	if (!iommu_is_paging_domain(domain))
 		return 0;
+	if (iommu_is_large_pages_domain(domain) && trusted)
+		return 0;
 
 	if (!(domain->pgsize_bitmap & (PAGE_SIZE | (PAGE_SIZE - 1)))) {
 		pr_warn("IOMMU pages cannot exactly represent CPU pages.\n");
@@ -2007,7 +2012,7 @@ static int __iommu_attach_device(struct iommu_domain *domain,
 	 * only limit domain->pgsize_bitmap after having attached the first
 	 * device.
 	 */
-	ret = iommu_check_page_size(domain);
+	ret = iommu_check_page_size(domain, dev);
 	if (ret) {
 		__iommu_detach_device(domain, dev);
 		return ret;
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index cabd25879613..1f1af59d0522 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -62,6 +62,8 @@ struct iommu_domain_geometry {
 					      implementation              */
 #define __IOMMU_DOMAIN_PT	(1U << 2)  /* Domain is identity mapped   */
 #define __IOMMU_DOMAIN_DMA_FQ	(1U << 3)  /* DMA-API uses flush queue    */
+#define __IOMMU_DOMAIN_LP	(1U << 4)  /* Support for PAGE_SIZE smaller
+					      than IOMMU page size        */
 
 /*
  * This are the possible domain-types
@@ -81,10 +83,12 @@ struct iommu_domain_geometry {
 #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)
+				 __IOMMU_DOMAIN_DMA_API |       \
+				 __IOMMU_DOMAIN_LP)
 #define IOMMU_DOMAIN_DMA_FQ	(__IOMMU_DOMAIN_PAGING |	\
 				 __IOMMU_DOMAIN_DMA_API |	\
-				 __IOMMU_DOMAIN_DMA_FQ)
+				 __IOMMU_DOMAIN_DMA_FQ |        \
+				 __IOMMU_DOMAIN_LP)
 
 struct iommu_domain {
 	unsigned type;
@@ -106,6 +110,11 @@ static inline bool iommu_is_paging_domain(struct iommu_domain *domain)
 	return domain->type & __IOMMU_DOMAIN_PAGING;
 }
 
+static inline bool iommu_is_large_pages_domain(struct iommu_domain *domain)
+{
+	return domain->type & __IOMMU_DOMAIN_LP;
+}
+
 enum iommu_cap {
 	IOMMU_CAP_CACHE_COHERENCY,	/* IOMMU can enforce cache coherent DMA
 					   transactions */
-- 
2.25.1