linux-kernel - [PATCH v2 7/8] iommu: Introduce __IOMMU_DOMAIN

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Date:   Sat, 28 Aug 2021 17:36:41 +0200
From:   Sven Peter <sven@...npeter.dev>
To:     iommu@...ts.linux-foundation.org
Cc:     Sven Peter <sven@...npeter.dev>, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Arnd Bergmann <arnd@...nel.org>,
        Mohamed Mediouni <mohamed.mediouni@...amail.com>,
        Alexander Graf <graf@...zon.com>,
        Hector Martin <marcan@...can.st>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 7/8] iommu: Introduce __IOMMU_DOMAIN_LP

__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 devices to such domains and set the flag for
IOMMU_DOMAIN_DMA, which can now handle these situations.

Signed-off-by: Sven Peter <sven@...npeter.dev>
---
 drivers/iommu/iommu.c | 2 ++
 include/linux/iommu.h | 8 ++++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index f02b727d3054..77d1ee14c7d0 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1980,6 +1980,8 @@ static int iommu_check_page_size(struct iommu_domain *domain)
 {
 	if (!(domain->type & __IOMMU_DOMAIN_PAGING))
 		return 0;
+	if (domain->type & __IOMMU_DOMAIN_LP)
+		return 0;
 
 	if ((1 << __ffs(domain->pgsize_bitmap)) > PAGE_SIZE) {
 		pr_warn("IOMMU page size cannot represent CPU pages.\n");
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 6633040a13f9..40c1ad6be4e7 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;
-- 
2.25.1