linux-kernel - [RFC PATCH 3/3] iommu: Introduce __IOMMU_DOMAIN_LARGE

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Message-Id: <20210806155523.50429-4-sven@svenpeter.dev>
Date:   Fri,  6 Aug 2021 17:55:23 +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>, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 3/3] iommu: Introduce __IOMMU_DOMAIN_LARGE_PAGES

__IOMMU_DOMAIN_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 | 14 +++++++++-----
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 5854a4ef5681..f0bfd76187b1 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1970,6 +1970,8 @@ static int iommu_check_page_size(struct iommu_domain *domain)
 {
 	if (!(domain->type & __IOMMU_DOMAIN_PAGING))
 		return 0;
+	if (domain->type & __IOMMU_DOMAIN_LARGE_PAGES)
+		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 e552ecfefcf7..1f97eac8a4b0 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -56,10 +56,13 @@ struct iommu_domain_geometry {
 };
 
 /* Domain feature flags */
-#define __IOMMU_DOMAIN_PAGING	(1U << 0)  /* Support for iommu_map/unmap */
-#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_PAGING       (1U << 0)  /* Support for iommu_map/unmap */
+#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_LARGE_PAGES  (1U << 3)  /* Domain can handle IOMMU page
+						  sizes larger than the CPU
+						  page size                   */
 
 /*
  * This are the possible domain-types
@@ -77,7 +80,8 @@ 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_LARGE_PAGES)
 
 struct iommu_domain {
 	unsigned type;
-- 
2.25.1