[PATCH v7 01/24] mm: Add a PASID field to mm_struct

Jean-Philippe Brucker
2020-05-19T18:02:14Z

Some devices can tag their DMA requests with a 20-bit Process Address
Space ID (PASID), allowing them to access multiple address spaces. In
combination with recoverable I/O page faults (for example PCIe PRI),
PASID allows the IOMMU to share page tables with the MMU.

To make sure that a single PASID is allocated for each address space, as
required by Intel ENQCMD, store the PASID in the mm_struct. The IOMMU
driver is in charge of serializing modifications to the PASID field.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
include/linux/mm_types.h | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 4aba6c0c2ba8..8db647275817 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -534,6 +534,10 @@ struct mm_struct {
atomic_long_t hugetlb_usage;
#endif
struct work_struct async_put_work;
+#ifdef CONFIG_IOMMU_SUPPORT
+ /* Address space ID used by device DMA */
+ unsigned int pasid;
+#endif
} __randomize_layout;

/*