[PATCH v10 03/13] iommu/sva: Add PASID helpers

Jean-Philippe Brucker
2020-09-18T10:23:17Z

Let IOMMU drivers allocate a single PASID per mm. Store the mm in the
IOASID set to allow refcounting and searching mm by PASID, when handling
an I/O page fault.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
v10: small comment updates
---
drivers/iommu/Kconfig | 5 ++
drivers/iommu/Makefile | 1 +
drivers/iommu/iommu-sva-lib.h | 15 ++++++
drivers/iommu/iommu-sva-lib.c | 86 +++++++++++++++++++++++++++++++++++
4 files changed, 107 insertions(+)
create mode 100644 drivers/iommu/iommu-sva-lib.h
create mode 100644 drivers/iommu/iommu-sva-lib.c

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index bef5d75e306b..fb1787377eb6 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -103,6 +103,11 @@ config IOMMU_DMA
select IRQ_MSI_IOMMU
select NEED_SG_DMA_LENGTH

+# Shared Virtual Addressing library
+config IOMMU_SVA_LIB
+ bool
+ select IOASID
+
config FSL_PAMU
bool "Freescale IOMMU support"
depends on PCI
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index 11f1771104f3..61bd30cd8369 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -27,3 +27,4 @@ obj-$(CONFIG_FSL_PAMU) += fsl_pamu.o fsl_pamu_domain.o
obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu.o
obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o
+obj-$(CONFIG_IOMMU_SVA_LIB) += iommu-sva-lib.o
diff --git a/drivers/iommu/iommu-sva-lib.h b/drivers/iommu/iommu-sva-lib.h
new file mode 100644
index 000000000000..b40990aef3fd
--- /dev/null
+++ b/drivers/iommu/iommu-sva-lib.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * SVA library for IOMMU drivers
+ */
+#ifndef _IOMMU_SVA_LIB_H
+#define _IOMMU_SVA_LIB_H
+
+#include <linux/ioasid.h>
+#include <linux/mm_types.h>
+
+int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max);
+void iommu_sva_free_pasid(struct mm_struct *mm);
+struct mm_struct *iommu_sva_find(ioasid_t pasid);
+
+#endif /* _IOMMU_SVA_LIB_H */
diff --git a/drivers/iommu/iommu-sva-lib.c b/drivers/iommu/iommu-sva-lib.c
new file mode 100644
index 000000000000..bd41405d34e9
--- /dev/null
+++ b/drivers/iommu/iommu-sva-lib.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Helpers for IOMMU drivers implementing SVA
+ */
+#include <linux/mutex.h>
+#include <linux/sched/mm.h>
+
+#include "iommu-sva-lib.h"
+
+static DEFINE_MUTEX(iommu_sva_lock);
+static DECLARE_IOASID_SET(iommu_sva_pasid);
+
+/**
+ * iommu_sva_alloc_pasid - Allocate a PASID for the mm
+ * @mm: the mm
+ * @min: minimum PASID value (inclusive)
+ * @max: maximum PASID value (inclusive)
+ *
+ * Try to allocate a PASID for this mm, or take a reference to the existing one
+ * provided it fits within the [@min, @max] range. On success the PASID is
+ * available in mm->pasid, and must be released with iommu_sva_free_pasid().
+ * @min must be greater than 0, because 0 indicates an unused mm->pasid.
+ *
+ * Returns 0 on success and < 0 on error.
+ */
+int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
+{
+ int ret = 0;
+ ioasid_t pasid;
+
+ if (min == INVALID_IOASID || max == INVALID_IOASID ||
+ min == 0 || max < min)
+ return -EINVAL;
+
+ mutex_lock(&iommu_sva_lock);
+ if (mm->pasid) {
+ if (mm->pasid >= min && mm->pasid <= max)
+ ioasid_get(mm->pasid);
+ else
+ ret = -EOVERFLOW;
+ } else {
+ pasid = ioasid_alloc(&iommu_sva_pasid, min, max, mm);
+ if (pasid == INVALID_IOASID)
+ ret = -ENOMEM;
+ else
+ mm->pasid = pasid;
+ }
+ mutex_unlock(&iommu_sva_lock);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(iommu_sva_alloc_pasid);
+
+/**
+ * iommu_sva_free_pasid - Release the mm's PASID
+ * @mm: the mm
+ *
+ * Drop one reference to a PASID allocated with iommu_sva_alloc_pasid()
+ */
+void iommu_sva_free_pasid(struct mm_struct *mm)
+{
+ mutex_lock(&iommu_sva_lock);
+ if (ioasid_put(mm->pasid))
+ mm->pasid = 0;
+ mutex_unlock(&iommu_sva_lock);
+}
+EXPORT_SYMBOL_GPL(iommu_sva_free_pasid);
+
+/* ioasid_find getter() requires a void * argument */
+static bool __mmget_not_zero(void *mm)
+{
+ return mmget_not_zero(mm);
+}
+
+/**
+ * iommu_sva_find() - Find mm associated to the given PASID
+ * @pasid: Process Address Space ID assigned to the mm
+ *
+ * On success a reference to the mm is taken, and must be released with mmput().
+ *
+ * Returns the mm corresponding to this PASID, or an error if not found.
+ */
+struct mm_struct *iommu_sva_find(ioasid_t pasid)
+{
+ return ioasid_find(&iommu_sva_pasid, pasid, __mmget_not_zero);
+}
+EXPORT_SYMBOL_GPL(iommu_sva_find);
--
2.28.0