[RFC PATCH 08/14] iommufd: Track the domains of revocable pages in struct iopt_pages

[Fred Griffoul <griffoul@gmail.com>]

From: Fred Griffoul <fgriffo@amazon.co.uk>

guest_memfd pages, like dma-buf pages, can be taken away from iommufd
whatever references it holds, but the list of (area, domain) pairs to
unmap on a revoke lives in struct iopt_pages_dmabuf.

Move it to struct iopt_pages, rename the iopt_dmabuf_*track* helpers to
iopt_pages_*, and add iopt_pages_tracked() for the page types that need
it, so that other page types can use it. No functional change.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Fred Griffoul <fgriffo@amazon.co.uk>
---
 drivers/iommu/iommufd/io_pagetable.c | 24 +++++-----
 drivers/iommu/iommufd/io_pagetable.h | 33 +++++++++-----
 drivers/iommu/iommufd/pages.c        | 67 ++++++++++++++--------------
 3 files changed, 67 insertions(+), 57 deletions(-)

diff --git a/drivers/iommu/iommufd/io_pagetable.c b/drivers/iommu/iommufd/io_pagetable.c
index 4e447ce74cf6..43d518e4ce58 100644
--- a/drivers/iommu/iommufd/io_pagetable.c
+++ b/drivers/iommu/iommufd/io_pagetable.c
@@ -1086,14 +1086,14 @@ static void iopt_unfill_domain(struct io_pagetable *iopt,
 				WARN_ON(!area->storage_domain);
 			if (area->storage_domain == domain)
 				area->storage_domain = storage_domain;
-			if (iopt_is_dmabuf(pages)) {
+			if (iopt_pages_tracked(pages)) {
 				if (!iopt_dmabuf_revoked(pages))
 					iopt_area_unmap_domain(area, domain);
-				iopt_dmabuf_untrack_domain(pages, area, domain);
+				iopt_pages_untrack_domain(pages, area, domain);
 			}
 			mutex_unlock(&pages->mutex);
 
-			if (!iopt_is_dmabuf(pages))
+			if (!iopt_pages_tracked(pages))
 				iopt_area_unmap_domain(area, domain);
 		}
 		return;
@@ -1111,8 +1111,8 @@ static void iopt_unfill_domain(struct io_pagetable *iopt,
 		WARN_ON(area->storage_domain != domain);
 		area->storage_domain = NULL;
 		iopt_area_unfill_domain(area, pages, domain);
-		if (iopt_is_dmabuf(pages))
-			iopt_dmabuf_untrack_domain(pages, area, domain);
+		if (iopt_pages_tracked(pages))
+			iopt_pages_untrack_domain(pages, area, domain);
 		mutex_unlock(&pages->mutex);
 	}
 }
@@ -1143,15 +1143,15 @@ static int iopt_fill_domain(struct io_pagetable *iopt,
 			continue;
 
 		guard(mutex)(&pages->mutex);
-		if (iopt_is_dmabuf(pages)) {
-			rc = iopt_dmabuf_track_domain(pages, area, domain);
+		if (iopt_pages_tracked(pages)) {
+			rc = iopt_pages_track_domain(pages, area, domain);
 			if (rc)
 				goto out_unfill;
 		}
 		rc = iopt_area_fill_domain(area, domain);
 		if (rc) {
-			if (iopt_is_dmabuf(pages))
-				iopt_dmabuf_untrack_domain(pages, area, domain);
+			if (iopt_pages_tracked(pages))
+				iopt_pages_untrack_domain(pages, area, domain);
 			goto out_unfill;
 		}
 		if (!area->storage_domain) {
@@ -1180,8 +1180,8 @@ static int iopt_fill_domain(struct io_pagetable *iopt,
 			area->storage_domain = NULL;
 		}
 		iopt_area_unfill_domain(area, pages, domain);
-		if (iopt_is_dmabuf(pages))
-			iopt_dmabuf_untrack_domain(pages, area, domain);
+		if (iopt_pages_tracked(pages))
+			iopt_pages_untrack_domain(pages, area, domain);
 		mutex_unlock(&pages->mutex);
 	}
 	return rc;
@@ -1393,7 +1393,7 @@ static int iopt_area_split(struct iopt_area *area, unsigned long iova)
 		return -EBUSY;
 
 	/* Maintaining the domains_itree below is a bit complicated */
-	if (iopt_is_dmabuf(pages))
+	if (iopt_pages_tracked(pages))
 		return -EOPNOTSUPP;
 
 	if (new_start & (alignment - 1) ||
diff --git a/drivers/iommu/iommufd/io_pagetable.h b/drivers/iommu/iommufd/io_pagetable.h
index 27e3e311d395..0dddfb5db5fd 100644
--- a/drivers/iommu/iommufd/io_pagetable.h
+++ b/drivers/iommu/iommufd/io_pagetable.h
@@ -70,15 +70,14 @@ void iopt_area_unfill_domain(struct iopt_area *area, struct iopt_pages *pages,
 void iopt_area_unmap_domain(struct iopt_area *area,
 			    struct iommu_domain *domain);
 
-int iopt_dmabuf_track_domain(struct iopt_pages *pages, struct iopt_area *area,
-			     struct iommu_domain *domain);
-void iopt_dmabuf_untrack_domain(struct iopt_pages *pages,
-				struct iopt_area *area,
-				struct iommu_domain *domain);
-int iopt_dmabuf_track_all_domains(struct iopt_area *area,
-				  struct iopt_pages *pages);
-void iopt_dmabuf_untrack_all_domains(struct iopt_area *area,
-				     struct iopt_pages *pages);
+int iopt_pages_track_domain(struct iopt_pages *pages, struct iopt_area *area,
+			    struct iommu_domain *domain);
+void iopt_pages_untrack_domain(struct iopt_pages *pages, struct iopt_area *area,
+			       struct iommu_domain *domain);
+int iopt_pages_track_all_domains(struct iopt_area *area,
+				 struct iopt_pages *pages);
+void iopt_pages_untrack_all_domains(struct iopt_area *area,
+				    struct iopt_pages *pages);
 
 static inline unsigned long iopt_area_index(struct iopt_area *area)
 {
@@ -194,7 +193,8 @@ enum iopt_address_type {
 	IOPT_ADDRESS_DMABUF,
 };
 
-struct iopt_pages_dmabuf_track {
+/* One (area, domain) mapping of revocable pages, on iopt_pages::tracker. */
+struct iopt_pages_track {
 	struct iommu_domain *domain;
 	struct iopt_area *area;
 	struct list_head elm;
@@ -205,7 +205,6 @@ struct iopt_pages_dmabuf {
 	struct phys_vec phys;
 	/* Always PAGE_SIZE aligned */
 	unsigned long start;
-	struct list_head tracker;
 };
 
 /*
@@ -246,6 +245,12 @@ struct iopt_pages {
 	struct rb_root_cached access_itree;
 	/* Of iopt_area::pages_node */
 	struct rb_root_cached domains_itree;
+	/*
+	 * Of iopt_pages_track::elm.  The owner of these pages can revoke them
+	 * whatever references iommufd holds, so every (area, domain) that
+	 * maps them is listed here for the revoke.  See iopt_pages_tracked().
+	 */
+	struct list_head tracker;
 };
 
 static inline bool iopt_is_dmabuf(struct iopt_pages *pages)
@@ -255,6 +260,12 @@ static inline bool iopt_is_dmabuf(struct iopt_pages *pages)
 	return pages->type == IOPT_ADDRESS_DMABUF;
 }
 
+/* The owner of the pages can revoke them, so their domains are tracked. */
+static inline bool iopt_pages_tracked(struct iopt_pages *pages)
+{
+	return iopt_is_dmabuf(pages);
+}
+
 static inline bool iopt_dmabuf_revoked(struct iopt_pages *pages)
 {
 	lockdep_assert_held(&pages->mutex);
diff --git a/drivers/iommu/iommufd/pages.c b/drivers/iommu/iommufd/pages.c
index 404f31d8f729..cf0f08c4e9a6 100644
--- a/drivers/iommu/iommufd/pages.c
+++ b/drivers/iommu/iommufd/pages.c
@@ -1384,6 +1384,7 @@ static struct iopt_pages *iopt_alloc_pages(unsigned long start_byte,
 	pages->npages = DIV_ROUND_UP(length + start_byte, PAGE_SIZE);
 	pages->access_itree = RB_ROOT_CACHED;
 	pages->domains_itree = RB_ROOT_CACHED;
+	INIT_LIST_HEAD(&pages->tracker);
 	pages->writable = writable;
 	if (capable(CAP_IPC_LOCK))
 		pages->account_mode = IOPT_PAGES_ACCOUNT_NONE;
@@ -1434,13 +1435,13 @@ struct iopt_pages *iopt_alloc_file_pages(struct file *file,
 static void iopt_revoke_notify(struct dma_buf_attachment *attach)
 {
 	struct iopt_pages *pages = attach->importer_priv;
-	struct iopt_pages_dmabuf_track *track;
+	struct iopt_pages_track *track;
 
 	guard(mutex)(&pages->mutex);
 	if (iopt_dmabuf_revoked(pages))
 		return;
 
-	list_for_each_entry(track, &pages->dmabuf.tracker, elm) {
+	list_for_each_entry(track, &pages->tracker, elm) {
 		struct iopt_area *area = track->area;
 
 		iopt_area_unmap_domain_range(area, track->domain,
@@ -1557,7 +1558,6 @@ struct iopt_pages *iopt_alloc_dmabuf_pages(struct iommufd_ctx *ictx,
 	pages->account_mode = IOPT_PAGES_ACCOUNT_NONE;
 	pages->type = IOPT_ADDRESS_DMABUF;
 	pages->dmabuf.start = start - start_byte;
-	INIT_LIST_HEAD(&pages->dmabuf.tracker);
 
 	rc = iopt_map_dmabuf(ictx, pages, dmabuf);
 	if (rc) {
@@ -1568,16 +1568,16 @@ struct iopt_pages *iopt_alloc_dmabuf_pages(struct iommufd_ctx *ictx,
 	return pages;
 }
 
-int iopt_dmabuf_track_domain(struct iopt_pages *pages, struct iopt_area *area,
-			     struct iommu_domain *domain)
+int iopt_pages_track_domain(struct iopt_pages *pages, struct iopt_area *area,
+			    struct iommu_domain *domain)
 {
-	struct iopt_pages_dmabuf_track *track;
+	struct iopt_pages_track *track;
 
 	lockdep_assert_held(&pages->mutex);
-	if (WARN_ON(!iopt_is_dmabuf(pages)))
+	if (WARN_ON(!iopt_pages_tracked(pages)))
 		return -EINVAL;
 
-	list_for_each_entry(track, &pages->dmabuf.tracker, elm)
+	list_for_each_entry(track, &pages->tracker, elm)
 		if (WARN_ON(track->domain == domain && track->area == area))
 			return -EINVAL;
 
@@ -1586,21 +1586,20 @@ int iopt_dmabuf_track_domain(struct iopt_pages *pages, struct iopt_area *area,
 		return -ENOMEM;
 	track->domain = domain;
 	track->area = area;
-	list_add_tail(&track->elm, &pages->dmabuf.tracker);
+	list_add_tail(&track->elm, &pages->tracker);
 
 	return 0;
 }
 
-void iopt_dmabuf_untrack_domain(struct iopt_pages *pages,
-				struct iopt_area *area,
-				struct iommu_domain *domain)
+void iopt_pages_untrack_domain(struct iopt_pages *pages, struct iopt_area *area,
+			       struct iommu_domain *domain)
 {
-	struct iopt_pages_dmabuf_track *track;
+	struct iopt_pages_track *track;
 
 	lockdep_assert_held(&pages->mutex);
-	WARN_ON(!iopt_is_dmabuf(pages));
+	WARN_ON(!iopt_pages_tracked(pages));
 
-	list_for_each_entry(track, &pages->dmabuf.tracker, elm) {
+	list_for_each_entry(track, &pages->tracker, elm) {
 		if (track->domain == domain && track->area == area) {
 			list_del(&track->elm);
 			kfree(track);
@@ -1610,36 +1609,36 @@ void iopt_dmabuf_untrack_domain(struct iopt_pages *pages,
 	WARN_ON(true);
 }
 
-int iopt_dmabuf_track_all_domains(struct iopt_area *area,
-				  struct iopt_pages *pages)
+int iopt_pages_track_all_domains(struct iopt_area *area,
+				 struct iopt_pages *pages)
 {
-	struct iopt_pages_dmabuf_track *track;
+	struct iopt_pages_track *track;
 	struct iommu_domain *domain;
 	unsigned long index;
 	int rc;
 
-	list_for_each_entry(track, &pages->dmabuf.tracker, elm)
+	list_for_each_entry(track, &pages->tracker, elm)
 		if (WARN_ON(track->area == area))
 			return -EINVAL;
 
 	xa_for_each(&area->iopt->domains, index, domain) {
-		rc = iopt_dmabuf_track_domain(pages, area, domain);
+		rc = iopt_pages_track_domain(pages, area, domain);
 		if (rc)
 			goto err_untrack;
 	}
 	return 0;
 err_untrack:
-	iopt_dmabuf_untrack_all_domains(area, pages);
+	iopt_pages_untrack_all_domains(area, pages);
 	return rc;
 }
 
-void iopt_dmabuf_untrack_all_domains(struct iopt_area *area,
-				     struct iopt_pages *pages)
+void iopt_pages_untrack_all_domains(struct iopt_area *area,
+				    struct iopt_pages *pages)
 {
-	struct iopt_pages_dmabuf_track *track;
-	struct iopt_pages_dmabuf_track *tmp;
+	struct iopt_pages_track *track;
+	struct iopt_pages_track *tmp;
 
-	list_for_each_entry_safe(track, tmp, &pages->dmabuf.tracker,
+	list_for_each_entry_safe(track, tmp, &pages->tracker,
 				 elm) {
 		if (track->area == area) {
 			list_del(&track->elm);
@@ -1656,6 +1655,7 @@ void iopt_release_pages(struct kref *kref)
 	WARN_ON(!RB_EMPTY_ROOT(&pages->domains_itree.rb_root));
 	WARN_ON(pages->npinned);
 	WARN_ON(!xa_empty(&pages->pinned_pfns));
+	WARN_ON(!list_empty(&pages->tracker));
 	if (iopt_is_dmabuf(pages) && pages->dmabuf.attach) {
 		struct dma_buf *dmabuf = pages->dmabuf.attach->dmabuf;
 
@@ -1664,7 +1664,6 @@ void iopt_release_pages(struct kref *kref)
 		dma_resv_unlock(dmabuf->resv);
 		dma_buf_detach(dmabuf, pages->dmabuf.attach);
 		dma_buf_put(dmabuf);
-		WARN_ON(!list_empty(&pages->dmabuf.tracker));
 	} else if (pages->type == IOPT_ADDRESS_FILE) {
 		fput(pages->file);
 	}
@@ -1749,7 +1748,7 @@ static void __iopt_area_unfill_domain(struct iopt_area *area,
 
 	lockdep_assert_held(&pages->mutex);
 
-	if (iopt_is_dmabuf(pages)) {
+	if (iopt_pages_tracked(pages)) {
 		if (WARN_ON(iopt_dmabuf_revoked(pages)))
 			return;
 		iopt_area_unmap_domain_range(area, domain, start_index,
@@ -1917,8 +1916,8 @@ int iopt_area_fill_domains(struct iopt_area *area, struct iopt_pages *pages)
 		return 0;
 
 	mutex_lock(&pages->mutex);
-	if (iopt_is_dmabuf(pages)) {
-		rc = iopt_dmabuf_track_all_domains(area, pages);
+	if (iopt_pages_tracked(pages)) {
+		rc = iopt_pages_track_all_domains(area, pages);
 		if (rc)
 			goto out_unlock;
 	}
@@ -1983,8 +1982,8 @@ int iopt_area_fill_domains(struct iopt_area *area, struct iopt_pages *pages)
 	}
 	pfn_reader_destroy(&pfns);
 out_untrack:
-	if (iopt_is_dmabuf(pages))
-		iopt_dmabuf_untrack_all_domains(area, pages);
+	if (iopt_pages_tracked(pages))
+		iopt_pages_untrack_all_domains(area, pages);
 out_unlock:
 	mutex_unlock(&pages->mutex);
 	return rc;
@@ -2024,8 +2023,8 @@ void iopt_area_unfill_domains(struct iopt_area *area, struct iopt_pages *pages)
 		WARN_ON(RB_EMPTY_NODE(&area->pages_node.rb));
 	interval_tree_remove(&area->pages_node, &pages->domains_itree);
 	iopt_area_unfill_domain(area, pages, area->storage_domain);
-	if (iopt_is_dmabuf(pages))
-		iopt_dmabuf_untrack_all_domains(area, pages);
+	if (iopt_pages_tracked(pages))
+		iopt_pages_untrack_all_domains(area, pages);
 	area->storage_domain = NULL;
 out_unlock:
 	mutex_unlock(&pages->mutex);
-- 
2.47.3