linux-kernel - [RFC PATCH 05/15] iommu: Introduce API to preserve iommu domain

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Message-ID: <20250928190624.3735830-6-skhawaja@google.com>
Date: Sun, 28 Sep 2025 19:06:13 +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>, 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, zhuyifei@...gle.com, 
	Chris Li <chrisl@...nel.org>, praan@...gle.com
Subject: [RFC PATCH 05/15] iommu: Introduce API to preserve iommu domain

Add an API that can be called by the iommu users to preserve iommu
domain. Currently it only marks the iommu_domain as preserved.

Signed-off-by: Samiullah Khawaja <skhawaja@...gle.com>
---
 drivers/iommu/iommu.c | 20 ++++++++++++++++++++
 include/linux/iommu.h | 10 ++++++++++
 2 files changed, 30 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index bfa7c8653720..2e6e9c3f26ec 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2002,6 +2002,10 @@ static void iommu_domain_init(struct iommu_domain *domain, unsigned int type,
 	domain->owner = ops;
 	if (!domain->ops)
 		domain->ops = ops->default_domain_ops;
+
+#ifdef CONFIG_LIVEUPDATE
+	atomic_set(&domain->preserved, 0);
+#endif
 }
 
 static struct iommu_domain *
@@ -2054,6 +2058,22 @@ EXPORT_SYMBOL_GPL(iommu_paging_domain_alloc_flags);
 
 #ifdef CONFIG_LIVEUPDATE
 DECLARE_RWSEM(liveupdate_state_rwsem);
+
+int iommu_domain_preserve(struct iommu_domain *domain)
+{
+	int ret;
+
+	lockdep_assert_held(&liveupdate_state_rwsem);
+	if (!domain->ops->preserve)
+		return -EOPNOTSUPP;
+
+	ret = domain->ops->preserve(domain);
+	if (!ret)
+		atomic_set(&domain->preserved, 1);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iommu_domain_preserve);
 #endif
 
 void iommu_domain_free(struct iommu_domain *domain)
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 40801d8eac61..aafd06134f5c 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -14,6 +14,7 @@
 #include <linux/err.h>
 #include <linux/of.h>
 #include <linux/iova_bitmap.h>
+#include <linux/atomic.h>
 #include <uapi/linux/iommufd.h>
 
 #define IOMMU_READ	(1 << 0)
@@ -248,6 +249,10 @@ struct iommu_domain {
 			struct list_head next;
 		};
 	};
+
+#ifdef CONFIG_LIVEUPDATE
+	atomic_t preserved;
+#endif
 };
 
 static inline bool iommu_is_dma_domain(struct iommu_domain *domain)
@@ -915,6 +920,11 @@ static inline struct iommu_domain *iommu_paging_domain_alloc(struct device *dev)
 {
 	return iommu_paging_domain_alloc_flags(dev, 0);
 }
+
+#ifdef CONFIG_LIVEUPDATE
+int iommu_domain_preserve(struct iommu_domain *domain);
+#endif
+
 extern void iommu_domain_free(struct iommu_domain *domain);
 extern int iommu_attach_device(struct iommu_domain *domain,
 			       struct device *dev);
-- 
2.51.0.536.g15c5d4f767-goog