[PATCH v4 03/21] iommu/dma: Add iommu_dma_sw_map_msi()

Add a descriptor-free counterpart to iommu_dma_sw_msi(). The existing
function is tied to a struct msi_desc and stores the result in the
descriptor. This variant returns the IOVA directly so callers can
pre-map MSI targets before any descriptor has been allocated.

Callers may pass a required mapping size so MSI doorbells that must
not share a larger IOMMU leaf, such as RISC-V IMSIC files, can fail
before a mapping is installed.

Signed-off-by: Andrew Jones <[email protected]>
---
 drivers/iommu/dma-iommu.c | 48 ++++++++++++++++++++++++++++++++-------
 drivers/iommu/dma-iommu.h | 12 ++++++++++
 2 files changed, 52 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 9a07eb39336e..3ce9f4878d92 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -2247,24 +2247,56 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev,
 	return NULL;
 }
 
-int iommu_dma_sw_msi(struct iommu_domain *domain, struct msi_desc *desc,
-		     phys_addr_t msi_addr)
+/*
+ * Descriptor-free counterpart to iommu_dma_sw_msi(). Maps an MSI physical
+ * page into the domain and returns the IOVA and mapping granule. Used for
+ * pre-mapping MSI targets before any MSI descriptor has been set.
+ *
+ * The caller must pass a device attached to @domain and hold @dev's IOMMU
+ * group mutex. If @required_size is non-zero then it must exactly match the
+ * domain's MSI mapping granule. @msi_iova and @msi_shift must be non-NULL.
+ */
+int iommu_dma_sw_map_msi(struct iommu_domain *domain,
+			 struct device *dev, phys_addr_t msi_addr,
+			 size_t required_size, dma_addr_t *msi_iova,
+			 unsigned int *msi_shift)
 {
-	struct device *dev = msi_desc_to_dev(desc);
 	const struct iommu_dma_msi_page *msi_page;
+	size_t size;
 
-	if (!has_msi_cookie(domain)) {
-		msi_desc_set_iommu_msi_iova(desc, 0, 0);
+	*msi_iova = 0;
+	*msi_shift = 0;
+
+	if (!has_msi_cookie(domain))
 		return 0;
-	}
+
+	size = cookie_msi_granule(domain);
+	if (required_size && size != required_size)
+		return -EOPNOTSUPP;
 
 	iommu_group_mutex_assert(dev);
 	msi_page = iommu_dma_get_msi_page(dev, msi_addr, domain);
 	if (!msi_page)
 		return -ENOMEM;
 
-	msi_desc_set_iommu_msi_iova(desc, msi_page->iova,
-				    ilog2(cookie_msi_granule(domain)));
+	*msi_iova = msi_page->iova;
+	*msi_shift = ilog2(size);
+	return 0;
+}
+
+int iommu_dma_sw_msi(struct iommu_domain *domain, struct msi_desc *desc,
+		     phys_addr_t msi_addr)
+{
+	struct device *dev = msi_desc_to_dev(desc);
+	dma_addr_t msi_iova;
+	unsigned int msi_shift;
+	int ret;
+
+	ret = iommu_dma_sw_map_msi(domain, dev, msi_addr, 0, &msi_iova, &msi_shift);
+	if (ret)
+		return ret;
+
+	msi_desc_set_iommu_msi_iova(desc, msi_iova, msi_shift);
 	return 0;
 }
 
diff --git a/drivers/iommu/dma-iommu.h b/drivers/iommu/dma-iommu.h
index 040d00252563..3e1adeafdcac 100644
--- a/drivers/iommu/dma-iommu.h
+++ b/drivers/iommu/dma-iommu.h
@@ -19,6 +19,10 @@ int iommu_dma_init_fq(struct iommu_domain *domain);
 
 void iommu_dma_get_resv_regions(struct device *dev, struct list_head *list);
 
+int iommu_dma_sw_map_msi(struct iommu_domain *domain,
+			 struct device *dev, phys_addr_t msi_addr,
+			 size_t required_size, dma_addr_t *msi_iova,
+			 unsigned int *msi_shift);
 int iommu_dma_sw_msi(struct iommu_domain *domain, struct msi_desc *desc,
 		     phys_addr_t msi_addr);
 
@@ -53,6 +57,14 @@ static inline void iommu_dma_get_resv_regions(struct device *dev, struct list_he
 {
 }
 
+static inline int iommu_dma_sw_map_msi(struct iommu_domain *domain,
+				       struct device *dev, phys_addr_t msi_addr,
+				       size_t required_size, dma_addr_t *msi_iova,
+				       unsigned int *msi_shift)
+{
+	return -ENODEV;
+}
+
 static inline int iommu_dma_sw_msi(struct iommu_domain *domain,
 				   struct msi_desc *desc, phys_addr_t msi_addr)
 {
-- 
2.43.0