linux-kernel - [RFC PATCH v2 20/32] iommu: Add APIs to get preserved state of a device

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Message-ID: <20251202230303.1017519-21-skhawaja@google.com>
Date: Tue,  2 Dec 2025 23:02:50 +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 20/32] iommu: Add APIs to get preserved state of a device

The preserved state of the device needs to be fetched at various places
during liveupdate. The added API can also be used to check if a device
is preserved or not. The API is only used during shutdown and after
liveupdate so no locking needed.

Signed-off-by: Samiullah Khawaja <skhawaja@...gle.com>
---
 include/linux/iommu-lu.h | 67 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/include/linux/iommu-lu.h b/include/linux/iommu-lu.h
index 95375530b7be..08a659de8553 100644
--- a/include/linux/iommu-lu.h
+++ b/include/linux/iommu-lu.h
@@ -8,9 +8,76 @@
 #ifndef _LINUX_IOMMU_LU_H
 #define _LINUX_IOMMU_LU_H
 
+#include <linux/device.h>
+#include <linux/iommu.h>
 #include <linux/liveupdate.h>
 #include <linux/kho/abi/iommu.h>
 
+#ifdef CONFIG_LIVEUPDATE
+static inline void *dev_iommu_preserved_state(struct device *dev)
+{
+	struct device_ser *ser;
+
+	ser = dev->iommu->device_ser;
+	if (ser && !ser->obj.incoming)
+		return ser;
+
+	return NULL;
+}
+
+static inline void *dev_iommu_restored_state(struct device *dev)
+{
+	struct device_ser *ser;
+
+	ser = dev->iommu->device_ser;
+	if (ser && ser->obj.incoming)
+		return ser;
+
+	return NULL;
+}
+
+static inline void *iommu_domain_restored_state(struct iommu_domain *domain)
+{
+	struct iommu_domain_ser *ser;
+
+	ser = domain->preserved_state;
+	if (ser && ser->obj.incoming)
+		return ser;
+
+	return NULL;
+}
+
+static inline int dev_iommu_restore_did(struct device *dev, struct iommu_domain *domain)
+{
+	struct device_ser *ser = dev_iommu_restored_state(dev);
+
+	if (ser && iommu_domain_restored_state(domain))
+		return ser->domain_iommu_ser.did;
+
+	return -1;
+}
+#else
+static inline void *dev_iommu_preserved_state(struct device *dev)
+{
+	return NULL;
+}
+
+static inline void *dev_iommu_restored_state(struct device *dev)
+{
+	return NULL;
+}
+
+static inline int dev_iommu_restore_did(struct device *dev, struct iommu_domain *domain)
+{
+	return -1;
+}
+
+static inline void *iommu_domain_restored_state(struct iommu_domain *domain)
+{
+	return NULL;
+}
+#endif
+
 int iommu_domain_preserve(struct iommu_domain *domain, struct iommu_domain_ser **ser);
 int iommu_domain_unpreserve(struct iommu_domain *domain);
 int iommu_preserve_device(struct iommu_domain *domain, struct device *dev);
-- 
2.52.0.158.g65b55ccf14-goog