[RFC PATCH 05/13] iommufd: Serialise persisted iommufds and ioas

[James Gowans <jgowans@amazon.com>]

Now actually implementing the serialise callback for iommufd.
On KHO activate, iterate through all persisted domains and write their
metadata to the device tree format. For now just a few fields are
serialised to demonstrate the concept. To actually make this useful a
lot more field and related objects will need to be serialised too.
---
 drivers/iommu/iommufd/iommufd_private.h |  2 +
 drivers/iommu/iommufd/main.c            |  2 +-
 drivers/iommu/iommufd/serialise.c       | 81 ++++++++++++++++++++++++-
 3 files changed, 81 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index a26728646a22..ad8d180269bd 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -18,6 +18,8 @@ struct iommu_group;
 struct iommu_option;
 struct iommufd_device;
 
+extern struct xarray persistent_iommufds;
+
 struct iommufd_ctx {
 	struct file *file;
 	struct xarray objects;
diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index fa4f0fe336ad..21a7e1ad40d1 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -30,7 +30,7 @@ struct iommufd_object_ops {
 static const struct iommufd_object_ops iommufd_object_ops[];
 static struct miscdevice vfio_misc_dev;
 
-static DEFINE_XARRAY_ALLOC(persistent_iommufds);
+DEFINE_XARRAY_ALLOC(persistent_iommufds);
 
 struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
 					     size_t size,
diff --git a/drivers/iommu/iommufd/serialise.c b/drivers/iommu/iommufd/serialise.c
index 6e8bcc384771..6b4c306dce40 100644
--- a/drivers/iommu/iommufd/serialise.c
+++ b/drivers/iommu/iommufd/serialise.c
@@ -1,19 +1,94 @@
 // SPDX-License-Identifier: GPL-2.0-only
 
 #include <linux/kexec.h>
+#include <linux/libfdt.h>
 #include "iommufd_private.h"
+#include "io_pagetable.h"
+
+/**
+ * Serialised format:
+ * /iommufd
+ *   compatible = "iommufd-v0",
+ *   iommufds = [
+ *     persistent_id = {
+ *       account_mode = u8
+ *       ioases = [
+ *         {
+ *           areas = [
+ *           ]
+ *         }
+ *       ]
+ *     }
+ *   ]
+ */
+static int serialise_iommufd(void *fdt, struct iommufd_ctx *ictx)
+{
+	int err = 0;
+	char name[24];
+	struct iommufd_object *obj;
+	unsigned long obj_idx;
+
+	snprintf(name, sizeof(name), "%lu", ictx->persistent_id);
+	err |= fdt_begin_node(fdt, name);
+	err |= fdt_begin_node(fdt, "ioases");
+	xa_for_each(&ictx->objects, obj_idx, obj) {
+		struct iommufd_ioas *ioas;
+		struct iopt_area *area;
+		int area_idx = 0;
+
+		if (obj->type != IOMMUFD_OBJ_IOAS)
+			continue;
+
+		ioas = (struct iommufd_ioas *) obj;
+		snprintf(name, sizeof(name), "%lu", obj_idx);
+		err |= fdt_begin_node(fdt, name);
+
+		for (area = iopt_area_iter_first(&ioas->iopt, 0, ULONG_MAX); area;
+				area = iopt_area_iter_next(area, 0, ULONG_MAX)) {
+			unsigned long iova_start, iova_len;
+
+			snprintf(name, sizeof(name), "%i", area_idx);
+			err |= fdt_begin_node(fdt, name);
+			iova_start = iopt_area_iova(area);
+			iova_len = iopt_area_length(area);
+			err |= fdt_property(fdt, "iova-start",
+					&iova_start, sizeof(iova_start));
+			err |= fdt_property(fdt, "iova-len",
+					&iova_len, sizeof(iova_len));
+			err |= fdt_property(fdt, "iommu-prot",
+					&area->iommu_prot, sizeof(area->iommu_prot));
+			err |= fdt_end_node(fdt); /* area_idx */
+			++area_idx;
+		}
+		err |= fdt_end_node(fdt); /* ioas obj_idx */
+	}
+	err |= fdt_end_node(fdt); /* ioases*/
+	err |= fdt_end_node(fdt); /* ictx->persistent_id */
+	return 0;
+}
 
 int iommufd_serialise_kho(struct notifier_block *self, unsigned long cmd,
 			  void *fdt)
 {
-	pr_info("would serialise here\n");
+	static const char compatible[] = "iommufd-v0";
+	struct iommufd_ctx *ictx;
+	unsigned long xa_idx;
+	int err = 0;
+
 	switch (cmd) {
 	case KEXEC_KHO_ABORT:
 		/* Would do serialise rollback here. */
 		return NOTIFY_DONE;
 	case KEXEC_KHO_DUMP:
-		/* Would do serialise here. */
-		return NOTIFY_DONE;
+		err |= fdt_begin_node(fdt, "iommufd");
+		fdt_property(fdt, "compatible", compatible, sizeof(compatible));
+		err |= fdt_begin_node(fdt, "iommufds");
+		xa_for_each(&persistent_iommufds, xa_idx, ictx) {
+			err |= serialise_iommufd(fdt, ictx);
+		}
+		err |= fdt_end_node(fdt); /* iommufds */
+		err |= fdt_end_node(fdt); /* iommufd */
+		return err? NOTIFY_BAD : NOTIFY_DONE;
 	default:
 		return NOTIFY_BAD;
 	}
-- 
2.34.1