[PATCH v3 5/6] iommu: Introduce __IOMMU_DOMAIN_LP

Sven Peter
2021-10-19T16:39:16Z

__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@svenpeter.dev>
---
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