[RFC PATCH v1 6/8] iommufd: Install software MSI map ranges atomically

[Andrew Jones]

Add a range installation helper which installs every map in a contiguous
software MSI range and rolls back only mappings added by the failed
operation. Use the helper when replaying range mappings into a new
paging domain.

This prepares iommufd to publish and install physical address lists
without exposing partially installed ranges.

Signed-off-by: Andrew Jones <andrew.jones@xxxxxxxxxxxxxxxx>
---
 drivers/iommu/iommufd/driver.c | 76 ++++++++++++++++++++++++++++++----
 1 file changed, 68 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/iommufd/driver.c b/drivers/iommu/iommufd/driver.c
index 6a0527f4b058..a43a25078f87 100644
--- a/drivers/iommu/iommufd/driver.c
+++ b/drivers/iommu/iommufd/driver.c
@@ -178,6 +178,17 @@ int iommufd_viommu_report_event(struct iommufd_viommu *viommu,
 EXPORT_SYMBOL_NS_GPL(iommufd_viommu_report_event, "IOMMUFD");
 
 #ifdef CONFIG_IRQ_MSI_IOMMU
+static bool iommufd_sw_msi_range_index(const struct iommufd_sw_msi_map *map,
+				       const struct iommufd_sw_msi_map *base_map,
+				       unsigned int nr_addrs, unsigned int *index)
+{
+	if (map->sw_msi_start != base_map->sw_msi_start || map->pgoff < base_map->pgoff)
+		return false;
+
+	*index = map->pgoff - base_map->pgoff;
+	return *index < nr_addrs;
+}
+
 /*
  * Get an iommufd_sw_msi_map for the msi physical addresses requested by the irq
  * layer. The mapping to IOVA is global to the iommufd file descriptor, every
@@ -207,11 +218,7 @@ iommufd_sw_msi_get_map(struct iommufd_ctx *ictx, const phys_addr_t *phys_addrs,
 		list_for_each_entry(cur, &ictx->sw_msi_list, sw_msi_item) {
 			unsigned int index;
 
-			if (cur->sw_msi_start != sw_msi_range->start ||
-			    cur->pgoff < msi_map->pgoff)
-				continue;
-			index = cur->pgoff - msi_map->pgoff;
-			if (index >= nr_addrs)
+			if (!iommufd_sw_msi_range_index(cur, msi_map, nr_addrs, &index))
 				continue;
 			if (cur->msi_addr != phys_addrs[index])
 				break;
@@ -306,9 +313,9 @@ iommufd_sw_msi_alloc_map(struct iommufd_ctx *ictx, const phys_addr_t *phys_addrs
 	return ERR_PTR(-ENOMEM);
 }
 
-int iommufd_sw_msi_install(struct iommufd_ctx *ictx,
-			   struct iommufd_hwpt_paging *hwpt_paging,
-			   struct iommufd_sw_msi_map *msi_map)
+static int iommufd_sw_msi_install_one(struct iommufd_ctx *ictx,
+				      struct iommufd_hwpt_paging *hwpt_paging,
+				      struct iommufd_sw_msi_map *msi_map)
 {
 	unsigned long iova;
 	int rc;
@@ -332,6 +339,59 @@ int iommufd_sw_msi_install(struct iommufd_ctx *ictx,
 	__set_bit(msi_map->id, hwpt_paging->present_sw_msi.bitmap);
 	return 0;
 }
+
+int iommufd_sw_msi_install(struct iommufd_ctx *ictx,
+			   struct iommufd_hwpt_paging *hwpt_paging,
+			   struct iommufd_sw_msi_map *base_map)
+{
+	struct iommufd_sw_msi_map *msi_map;
+	struct list_head *msi_maps = &ictx->sw_msi_list;
+	unsigned long *newly_mapped;
+	unsigned int nr_addrs = base_map->range_size ? base_map->range_size / PAGE_SIZE : 1;
+	unsigned int nr_found = 0;
+	unsigned int index;
+	int rc = 0;
+
+	newly_mapped = bitmap_zalloc(nr_addrs, GFP_KERNEL_ACCOUNT);
+	if (!newly_mapped)
+		return -ENOMEM;
+
+	list_for_each_entry(msi_map, msi_maps, sw_msi_item) {
+		if (!iommufd_sw_msi_range_index(msi_map, base_map, nr_addrs, &index))
+			continue;
+		if (iommufd_sw_msi_maps_test_bit(&hwpt_paging->present_sw_msi, msi_map->id)) {
+			nr_found++;
+			continue;
+		}
+		rc = iommufd_sw_msi_install_one(ictx, hwpt_paging, msi_map);
+		if (rc)
+			goto err_unmap;
+		__set_bit(index, newly_mapped);
+		nr_found++;
+	}
+	if (nr_found != nr_addrs) {
+		rc = -EINVAL;
+		goto err_unmap;
+	}
+
+	bitmap_free(newly_mapped);
+	return 0;
+
+err_unmap:
+	list_for_each_entry(msi_map, msi_maps, sw_msi_item) {
+		unsigned long iova;
+
+		if (!iommufd_sw_msi_range_index(msi_map, base_map, nr_addrs, &index) ||
+		    !test_bit(index, newly_mapped))
+			continue;
+
+		iova = msi_map->sw_msi_start + msi_map->pgoff * PAGE_SIZE;
+		WARN_ON_ONCE(iommu_unmap(hwpt_paging->common.domain, iova, PAGE_SIZE) != PAGE_SIZE);
+		__clear_bit(msi_map->id, hwpt_paging->present_sw_msi.bitmap);
+	}
+	bitmap_free(newly_mapped);
+	return rc;
+}
 EXPORT_SYMBOL_NS_GPL(iommufd_sw_msi_install, "IOMMUFD_INTERNAL");
 
 /*
-- 
2.43.0