[PATCH v6 02/16] iommufd: Convert struct iommufd_sw_msi_maps to a growable bitmap

[Andrew Jones <andrew.jones@oss.qualcomm.com>]

struct iommufd_sw_msi_maps uses a fixed 64-bit bitmap, limiting each
group and hardware page table to 64 software MSI mappings. RISC-V
interrupt remapping needs a mapping for every possible CPU, so this
limit is insufficient.

Make the bitmap grow on demand and treat IDs beyond its current size
as absent. Cap it at 16K entries to bound allocation size while leaving
ample room for expected software MSI users.

Signed-off-by: Andrew Jones <andrew.jones@oss.qualcomm.com>
Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>
Tested-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>
---
 drivers/iommu/iommufd/device.c          |  3 +-
 drivers/iommu/iommufd/driver.c          | 37 ++++++++++++++--------
 drivers/iommu/iommufd/hw_pagetable.c    |  1 +
 drivers/iommu/iommufd/iommufd_private.h | 41 +++++++++++++++++++++++--
 4 files changed, 66 insertions(+), 16 deletions(-)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index a664c70a6fe7..28e2c98ef953 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -49,6 +49,7 @@ static void iommufd_group_release(struct kref *kref)
 		iommu_group_put(igroup->group);
 	}
 	mutex_destroy(&igroup->lock);
+	kfree(igroup->required_sw_msi.bitmap);
 	kfree(igroup);
 }
 
@@ -450,7 +451,7 @@ static int iommufd_group_setup_msi(struct iommufd_group *igroup,
 		int rc;
 
 		if (cur->sw_msi_start != igroup->sw_msi_start ||
-		    !test_bit(cur->id, igroup->required_sw_msi.bitmap))
+		    !iommufd_sw_msi_maps_test_bit(&igroup->required_sw_msi, cur->id))
 			continue;
 
 		rc = iommufd_sw_msi_install(ictx, hwpt_paging, cur);
diff --git a/drivers/iommu/iommufd/driver.c b/drivers/iommu/iommufd/driver.c
index e4d17a748178..ea705e416139 100644
--- a/drivers/iommu/iommufd/driver.c
+++ b/drivers/iommu/iommufd/driver.c
@@ -196,13 +196,15 @@ iommufd_sw_msi_get_map(struct iommufd_ctx *ictx, phys_addr_t msi_addr,
 	list_for_each_entry(cur, &ictx->sw_msi_list, sw_msi_item) {
 		if (cur->sw_msi_start != sw_msi_start)
 			continue;
+		if (cur->pgoff == UINT_MAX)
+			return ERR_PTR(-EOVERFLOW);
 		max_pgoff = max(max_pgoff, cur->pgoff + 1);
 		if (cur->msi_addr == msi_addr)
 			return cur;
 	}
 
-	if (ictx->sw_msi_id >=
-	    BITS_PER_BYTE * sizeof_field(struct iommufd_sw_msi_maps, bitmap))
+	if (ictx->sw_msi_id > IOMMUFD_SW_MSI_MAX_ID ||
+	    max_pgoff > (ULONG_MAX - sw_msi_start) / PAGE_SIZE)
 		return ERR_PTR(-EOVERFLOW);
 
 	cur = kzalloc_obj(*cur);
@@ -222,21 +224,25 @@ int iommufd_sw_msi_install(struct iommufd_ctx *ictx,
 			   struct iommufd_sw_msi_map *msi_map)
 {
 	unsigned long iova;
+	int rc;
 
 	lockdep_assert_held(&ictx->sw_msi_lock);
 
+	if (iommufd_sw_msi_maps_test_bit(&hwpt_paging->present_sw_msi, msi_map->id))
+		return 0;
+
 	iova = msi_map->sw_msi_start + msi_map->pgoff * PAGE_SIZE;
-	if (!test_bit(msi_map->id, hwpt_paging->present_sw_msi.bitmap)) {
-		int rc;
-
-		rc = iommu_map(hwpt_paging->common.domain, iova,
-			       msi_map->msi_addr, PAGE_SIZE,
-			       IOMMU_WRITE | IOMMU_READ | IOMMU_MMIO,
-			       GFP_KERNEL_ACCOUNT);
-		if (rc)
-			return rc;
-		__set_bit(msi_map->id, hwpt_paging->present_sw_msi.bitmap);
-	}
+	rc = iommufd_sw_msi_maps_ensure(&hwpt_paging->present_sw_msi, msi_map->id);
+	if (rc)
+		return rc;
+
+	rc = iommu_map(hwpt_paging->common.domain, iova,
+		       msi_map->msi_addr, PAGE_SIZE,
+		       IOMMU_WRITE | IOMMU_READ | IOMMU_MMIO,
+		       GFP_KERNEL_ACCOUNT);
+	if (rc)
+		return rc;
+	__set_bit(msi_map->id, hwpt_paging->present_sw_msi.bitmap);
 	return 0;
 }
 EXPORT_SYMBOL_NS_GPL(iommufd_sw_msi_install, "IOMMUFD_INTERNAL");
@@ -290,6 +296,11 @@ int iommufd_sw_msi(struct iommu_domain *domain, struct msi_desc *desc,
 	if (IS_ERR(msi_map))
 		return PTR_ERR(msi_map);
 
+	rc = iommufd_sw_msi_maps_ensure(&handle->idev->igroup->required_sw_msi,
+					msi_map->id);
+	if (rc)
+		return rc;
+
 	rc = iommufd_sw_msi_install(ictx, hwpt_paging, msi_map);
 	if (rc)
 		return rc;
diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c
index ef6e119c2a75..81f41d437c4c 100644
--- a/drivers/iommu/iommufd/hw_pagetable.c
+++ b/drivers/iommu/iommufd/hw_pagetable.c
@@ -41,6 +41,7 @@ void iommufd_hwpt_paging_destroy(struct iommufd_object *obj)
 	}
 
 	__iommufd_hwpt_destroy(&hwpt_paging->common);
+	kfree(hwpt_paging->present_sw_msi.bitmap);
 	refcount_dec(&hwpt_paging->ioas->obj.users);
 }
 
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index eb2e85b27e42..774cbe28cbaf 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -9,6 +9,7 @@
 #include <linux/iova_bitmap.h>
 #include <linux/maple_tree.h>
 #include <linux/rwsem.h>
+#include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/xarray.h>
 #include <uapi/linux/iommufd.h>
@@ -29,11 +30,47 @@ struct iommufd_sw_msi_map {
 	unsigned int id;
 };
 
-/* Bitmap of struct iommufd_sw_msi_map::id */
+/* Bitmap of struct iommufd_sw_msi_map::id; starts empty, grows on demand. */
 struct iommufd_sw_msi_maps {
-	DECLARE_BITMAP(bitmap, 64);
+	unsigned long *bitmap;
+	unsigned int nbits;
 };
 
+/* Large enough for foreseeable SW MSI users while bounding bitmap growth. */
+#define IOMMUFD_SW_MSI_MAX_ID	(16U * 1024 - 1)
+
+/* Grow bitmap to accommodate id. Must be called under ictx->sw_msi_lock. */
+static inline int iommufd_sw_msi_maps_ensure(struct iommufd_sw_msi_maps *maps,
+					     unsigned int id)
+{
+	unsigned long *new_bitmap;
+	unsigned int new_nbits;
+
+	if (id < maps->nbits)
+		return 0;
+	if (id > IOMMUFD_SW_MSI_MAX_ID)
+		return -EOVERFLOW;
+
+	new_nbits = max(ALIGN(id + 1, BITS_PER_LONG), 64U);
+	new_bitmap = krealloc(maps->bitmap,
+			      BITS_TO_LONGS(new_nbits) * sizeof(unsigned long),
+			      GFP_KERNEL_ACCOUNT);
+	if (!new_bitmap)
+		return -ENOMEM;
+	bitmap_clear(new_bitmap, maps->nbits, new_nbits - maps->nbits);
+	maps->bitmap = new_bitmap;
+	maps->nbits = new_nbits;
+	return 0;
+}
+
+static inline bool iommufd_sw_msi_maps_test_bit(const struct iommufd_sw_msi_maps *maps,
+						unsigned int id)
+{
+	if (id >= maps->nbits)
+		return false;
+	return test_bit(id, maps->bitmap);
+}
+
 #ifdef CONFIG_IRQ_MSI_IOMMU
 int iommufd_sw_msi_install(struct iommufd_ctx *ictx,
 			   struct iommufd_hwpt_paging *hwpt_paging,
-- 
2.43.0