linux-kernel - [RFC PATCH v2 23/32] iommu: Add an API get the preserved state of an IOMMU

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Message-ID: <20251202230303.1017519-24-skhawaja@google.com>
Date: Tue,  2 Dec 2025 23:02:53 +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 23/32] iommu: Add an API get the preserved state of an IOMMU

After liveupdate kexec during boot, the state of the preserved IOMMU
needs to be restored. Since the state needs to be restored by the IOMMU
drivers during initialization/registration with the IOMMU core, add an
API that can be used by the IOMMU drivers to fetch the preserved state.

Signed-off-by: Samiullah Khawaja <skhawaja@...gle.com>
---
 drivers/iommu/liveupdate.c | 29 +++++++++++++++++++++++++++++
 include/linux/iommu-lu.h   |  1 +
 2 files changed, 30 insertions(+)

diff --git a/drivers/iommu/liveupdate.c b/drivers/iommu/liveupdate.c
index 0dfa03673178..e7ecf2e9aa4e 100644
--- a/drivers/iommu/liveupdate.c
+++ b/drivers/iommu/liveupdate.c
@@ -175,6 +175,35 @@ int iommu_liveupdate_unregister_flb(struct liveupdate_file_handler *handler)
 }
 EXPORT_SYMBOL(iommu_liveupdate_unregister_flb);
 
+struct iommu_ser *iommu_get_preserved_data(u64 token, enum iommu_lu_type type)
+{
+	struct iommu_lu_flb_obj *obj;
+	struct iommus_ser *iommus;
+	int ret, i, idx;
+
+	ret = liveupdate_flb_get_incoming(&iommu_flb, (void **)&obj);
+	if (ret)
+		return NULL;
+
+	iommus = __va(obj->ser->iommus_phys);
+	for (i = 0, idx = 0; i < obj->ser->nr_iommus; ++i, ++idx) {
+		if (idx >= MAX_IOMMU_SERS) {
+			iommus = __va(iommus->objs.next_objs);
+			idx = 0;
+		}
+
+		if (iommus->iommus[idx].obj.deleted)
+			continue;
+
+		if (iommus->iommus[idx].token == token &&
+		    iommus->iommus[idx].type == type)
+			return &iommus->iommus[idx];
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL(iommu_get_preserved_data);
+
 static int reserve_obj_ser(struct iommu_objs_ser **objs_ptr, u64 max_objs)
 {
 	struct iommu_objs_ser *next_objs, *objs = *objs_ptr;
diff --git a/include/linux/iommu-lu.h b/include/linux/iommu-lu.h
index 08a659de8553..ffce7043e997 100644
--- a/include/linux/iommu-lu.h
+++ b/include/linux/iommu-lu.h
@@ -78,6 +78,7 @@ static inline void *iommu_domain_restored_state(struct iommu_domain *domain)
 }
 #endif
 
+struct iommu_ser *iommu_get_preserved_data(u64 token, enum iommu_lu_type type);
 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