linux-kernel - [RFC PATCH v2 13/32] iommu: Add APIs to preserve/unpreserve iommu domains

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Message-ID: <20251202230303.1017519-14-skhawaja@google.com>
Date: Tue,  2 Dec 2025 23:02:43 +0000
From: Samiullah Khawaja <skhawaja@...gle.com>
To: David Woodhouse <dwmw2@...radead.org>, Lu Baolu <baolu.lu@...ux.intel.com>, 
	Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>, 
	Pasha Tatashin <pasha.tatashin@...een.com>, Jason Gunthorpe <jgg@...pe.ca>, iommu@...ts.linux.dev
Cc: Samiullah Khawaja <skhawaja@...gle.com>, Robin Murphy <robin.murphy@....com>, 
	Pratyush Yadav <pratyush@...nel.org>, Kevin Tian <kevin.tian@...el.com>, 
	Alex Williamson <alex@...zbot.org>, linux-kernel@...r.kernel.org, 
	Saeed Mahameed <saeedm@...dia.com>, Adithya Jayachandran <ajayachandra@...dia.com>, 
	Parav Pandit <parav@...dia.com>, Leon Romanovsky <leonro@...dia.com>, William Tu <witu@...dia.com>, 
	Vipin Sharma <vipinsh@...gle.com>, dmatlack@...gle.com, YiFei Zhu <zhuyifei@...gle.com>, 
	Chris Li <chrisl@...nel.org>, praan@...gle.com
Subject: [RFC PATCH v2 13/32] iommu: Add APIs to preserve/unpreserve iommu domains

These APIs will be used by iommufd LU handler to preserve and unpreserve
a domain for live update.

Signed-off-by: Samiullah Khawaja <skhawaja@...gle.com>
---
 drivers/iommu/liveupdate.c | 82 ++++++++++++++++++++++++++++++++++++++
 include/linux/iommu-lu.h   |  2 +
 include/linux/iommu.h      |  4 ++
 3 files changed, 88 insertions(+)

diff --git a/drivers/iommu/liveupdate.c b/drivers/iommu/liveupdate.c
index 21ce7be9b87e..25a943e5e1e3 100644
--- a/drivers/iommu/liveupdate.c
+++ b/drivers/iommu/liveupdate.c
@@ -127,3 +127,85 @@ int iommu_liveupdate_unregister_flb(struct liveupdate_file_handler *handler)
 	return liveupdate_unregister_flb(handler, &iommu_flb);
 }
 EXPORT_SYMBOL(iommu_liveupdate_unregister_flb);
+
+static int reserve_obj_ser(struct iommu_objs_ser **objs_ptr, u64 max_objs)
+{
+	struct iommu_objs_ser *next_objs, *objs = *objs_ptr;
+	int idx;
+
+	if (objs->nr_objs == max_objs) {
+		next_objs = kho_alloc_preserve(PAGE_SIZE);
+		if (!next_objs)
+			return -ENOMEM;
+
+		objs->next_objs = virt_to_phys(next_objs);
+		objs = next_objs;
+		*objs_ptr = objs;
+		objs->nr_objs = 0;
+	}
+
+	idx = objs->nr_objs++;
+	return idx;
+}
+
+int iommu_domain_preserve(struct iommu_domain *domain, struct iommu_domain_ser **ser)
+{
+	struct iommu_domain_ser *domain_ser;
+	struct iommu_lu_flb_obj *flb_obj;
+	int idx, ret;
+
+	if (!domain->ops->preserve)
+		return -EOPNOTSUPP;
+
+	ret = liveupdate_flb_get_outgoing(&iommu_flb, (void **)&flb_obj);
+	if (ret)
+		return ret;
+
+	guard(mutex)(&flb_obj->lock);
+	idx = reserve_obj_ser((struct iommu_objs_ser **)&flb_obj->iommu_domains,
+			      MAX_IOMMU_DOMAIN_SERS);
+	if (idx < 0)
+		return idx;
+
+	domain_ser = &flb_obj->iommu_domains->iommu_domains[idx];
+	idx = flb_obj->ser->nr_domains++;
+	domain_ser->obj.idx = idx;
+	domain_ser->obj.ref_count = 1;
+
+	ret = domain->ops->preserve(domain, domain_ser);
+	if (ret) {
+		domain_ser->obj.deleted = true;
+		return ret;
+	}
+
+	domain->preserved_state = domain_ser;
+	*ser = domain_ser;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(iommu_domain_preserve);
+
+int iommu_domain_unpreserve(struct iommu_domain *domain)
+{
+	struct iommu_domain_ser *domain_ser;
+	struct iommu_lu_flb_obj *flb_obj;
+	int ret;
+
+	if (!domain->ops->unpreserve)
+		return -EOPNOTSUPP;
+
+	ret = liveupdate_flb_get_outgoing(&iommu_flb, (void **)&flb_obj);
+	if (ret)
+		return ret;
+
+	guard(mutex)(&flb_obj->lock);
+	domain_ser = domain->preserved_state;
+	if (domain_ser->attach_count)
+		ret = -EBUSY;
+
+	domain->ops->unpreserve(domain, domain_ser);
+	domain_ser->obj.deleted = true;
+	domain->preserved_state = NULL;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(iommu_domain_unpreserve);
diff --git a/include/linux/iommu-lu.h b/include/linux/iommu-lu.h
index 59095d2f1bb2..2c8e5ac746ad 100644
--- a/include/linux/iommu-lu.h
+++ b/include/linux/iommu-lu.h
@@ -11,6 +11,8 @@
 #include <linux/liveupdate.h>
 #include <linux/kho/abi/iommu.h>
 
+int iommu_domain_preserve(struct iommu_domain *domain, struct iommu_domain_ser **ser);
+int iommu_domain_unpreserve(struct iommu_domain *domain);
 int iommu_liveupdate_register_flb(struct liveupdate_file_handler *handler);
 int iommu_liveupdate_unregister_flb(struct liveupdate_file_handler *handler);
 
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index f681d4d27d6e..17e1f3c29958 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -249,6 +249,10 @@ struct iommu_domain {
 			struct list_head next;
 		};
 	};
+
+#ifdef CONFIG_LIVEUPDATE
+	struct iommu_domain_ser *preserved_state;
+#endif
 };
 
 static inline bool iommu_is_dma_domain(struct iommu_domain *domain)
-- 
2.52.0.158.g65b55ccf14-goog