[PATCH v2 02/14] iommufd: Add iommufd_sw_map_msi()

[Andrew Jones]

Add a descriptor-free counterpart to iommufd_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.

Signed-off-by: Andrew Jones <andrew.jones@xxxxxxxxxxxxxxxx>
---
 drivers/iommu/iommu-priv.h     | 11 +++++++
 drivers/iommu/iommufd/driver.c | 59 +++++++++++++++++++++++++---------
 2 files changed, 55 insertions(+), 15 deletions(-)

diff --git a/drivers/iommu/iommu-priv.h b/drivers/iommu/iommu-priv.h
index aaffad5854fc..f60373cd2f70 100644
--- a/drivers/iommu/iommu-priv.h
+++ b/drivers/iommu/iommu-priv.h
@@ -55,12 +55,23 @@ int iommu_replace_group_handle(struct iommu_group *group,
 #if IS_ENABLED(CONFIG_IOMMUFD_DRIVER_CORE) && IS_ENABLED(CONFIG_IRQ_MSI_IOMMU)
 int iommufd_sw_msi(struct iommu_domain *domain, struct msi_desc *desc,
 		   phys_addr_t msi_addr);
+int iommufd_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);
 #else /* !CONFIG_IOMMUFD_DRIVER_CORE || !CONFIG_IRQ_MSI_IOMMU */
 static inline int iommufd_sw_msi(struct iommu_domain *domain,
 				 struct msi_desc *desc, phys_addr_t msi_addr)
 {
 	return -EOPNOTSUPP;
 }
+
+static inline int iommufd_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 -EOPNOTSUPP;
+}
 #endif /* CONFIG_IOMMUFD_DRIVER_CORE && CONFIG_IRQ_MSI_IOMMU */
 
 int iommu_replace_device_pasid(struct iommu_domain *domain,
diff --git a/drivers/iommu/iommufd/driver.c b/drivers/iommu/iommufd/driver.c
index 3cd617dfc351..9aad5c69d4ac 100644
--- a/drivers/iommu/iommufd/driver.c
+++ b/drivers/iommu/iommufd/driver.c
@@ -249,15 +249,22 @@ int iommufd_sw_msi_install(struct iommufd_ctx *ictx,
 EXPORT_SYMBOL_NS_GPL(iommufd_sw_msi_install, "IOMMUFD_INTERNAL");
 
 /*
- * Called by the irq code if the platform translates the MSI address through the
- * IOMMU. msi_addr is the physical address of the MSI page. iommufd will
- * allocate a fd global iova for the physical page that is the same on all
- * domains and devices.
+ * Descriptor-free counterpart to iommufd_sw_msi(). Maps an MSI physical page
+ * into the domain and returns the IOVA. Used for pre-mapping MSI targets before
+ * any MSI descriptor has been set (e.g. IMSIC doorbell pages). The IOVA is
+ * global to the iommufd file descriptor: every domain and device using the
+ * same MSI parameters gets the same IOVA.
+ *
+ * msi_addr is the exact byte offset of the MSI doorbell; the caller must have
+ * verified it is contained within an MMIO region safe to map at PAGE_SIZE. If
+ * required_size is non-zero it must equal PAGE_SIZE.
+ *
+ * The caller must hold @dev's iommu group mutex.
  */
-int iommufd_sw_msi(struct iommu_domain *domain, struct msi_desc *desc,
-		   phys_addr_t msi_addr)
+int iommufd_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);
 	struct iommufd_hwpt_paging *hwpt_paging;
 	struct iommu_attach_handle *raw_handle;
 	struct iommufd_attach_handle *handle;
@@ -266,6 +273,12 @@ int iommufd_sw_msi(struct iommu_domain *domain, struct msi_desc *desc,
 	unsigned long iova;
 	int rc;
 
+	*msi_iova = 0;
+	*msi_shift = 0;
+
+	if (required_size && required_size != PAGE_SIZE)
+		return -EOPNOTSUPP;
+
 	/*
 	 * It is safe to call iommu_attach_handle_get() here because the iommu
 	 * core code invokes this under the group mutex which also prevents any
@@ -286,13 +299,7 @@ int iommufd_sw_msi(struct iommu_domain *domain, struct msi_desc *desc,
 
 	ictx = handle->idev->ictx;
 	guard(mutex)(&ictx->sw_msi_lock);
-	/*
-	 * The input msi_addr is the exact byte offset of the MSI doorbell, we
-	 * assume the caller has checked that it is contained with a MMIO region
-	 * that is secure to map at PAGE_SIZE.
-	 */
-	msi_map = iommufd_sw_msi_get_map(handle->idev->ictx,
-					 msi_addr & PAGE_MASK,
+	msi_map = iommufd_sw_msi_get_map(ictx, msi_addr & PAGE_MASK,
 					 handle->idev->igroup->sw_msi_start);
 	if (IS_ERR(msi_map))
 		return PTR_ERR(msi_map);
@@ -308,7 +315,29 @@ int iommufd_sw_msi(struct iommu_domain *domain, struct msi_desc *desc,
 	__set_bit(msi_map->id, handle->idev->igroup->required_sw_msi.bitmap);
 
 	iova = msi_map->sw_msi_start + msi_map->pgoff * PAGE_SIZE;
-	msi_desc_set_iommu_msi_iova(desc, iova, PAGE_SHIFT);
+	*msi_iova = iova;
+	*msi_shift = PAGE_SHIFT;
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_sw_map_msi, "IOMMUFD");
+
+/*
+ * Called by the irq layer when the platform translates MSI addresses through
+ * the IOMMU. Wraps iommufd_sw_map_msi() and stores the result in the descriptor.
+ */
+int iommufd_sw_msi(struct iommu_domain *domain, struct msi_desc *desc,
+		   phys_addr_t msi_addr)
+{
+	dma_addr_t msi_iova;
+	unsigned int msi_shift;
+	int rc;
+
+	rc = iommufd_sw_map_msi(domain, msi_desc_to_dev(desc), msi_addr,
+				0, &msi_iova, &msi_shift);
+	if (rc)
+		return rc;
+
+	msi_desc_set_iommu_msi_iova(desc, msi_iova, msi_shift);
 	return 0;
 }
 EXPORT_SYMBOL_NS_GPL(iommufd_sw_msi, "IOMMUFD");
-- 
2.43.0