linux-kernel - [RFC PATCH 13/15] iommufd: Persist iommu domains for live update

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Message-ID: <20250928190624.3735830-14-skhawaja@google.com>
Date: Sun, 28 Sep 2025 19:06:21 +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: YiFei Zhu <zhuyifei@...gle.com>, 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, Chris Li <chrisl@...nel.org>, 
	praan@...gle.com
Subject: [RFC PATCH 13/15] iommufd: Persist iommu domains for live update

From: YiFei Zhu <zhuyifei@...gle.com>

Iterate through all the IOAS objects and the underlying hwpt_paging
objects. Persist each iommu domain using API iommu_domain_preserve.

This is temporary as only the domains attached to the persisted devices
need to preserved.

Signed-off-by: YiFei Zhu <zhuyifei@...gle.com>
Signed-off-by: Samiullah Khawaja <skhawaja@...gle.com>
---
 drivers/iommu/iommufd/liveupdate.c | 47 ++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/drivers/iommu/iommufd/liveupdate.c b/drivers/iommu/iommufd/liveupdate.c
index 1bdd5a82af90..0af0c6fadff1 100644
--- a/drivers/iommu/iommufd/liveupdate.c
+++ b/drivers/iommu/iommufd/liveupdate.c
@@ -8,9 +8,52 @@
 #include <linux/kexec_handover.h>
 #include <linux/liveupdate.h>
 #include <linux/mm.h>
+#include <linux/pci.h>
 
 #include "iommufd_private.h"
 
+static int iommufd_save_ioas(struct iommufd_ctx *ictx,
+			     struct iommufd_lu *iommufd_lu)
+{
+	struct iommufd_hwpt_paging *hwpt_paging;
+	struct iommufd_ioas *ioas = NULL;
+	struct iommufd_object *obj;
+	unsigned long index;
+	int rc;
+
+	/* Iterate each ioas. */
+	xa_for_each(&ictx->objects, index, obj) {
+		if (obj->type != IOMMUFD_OBJ_IOAS)
+			continue;
+
+		ioas = (struct iommufd_ioas *)obj;
+		mutex_lock(&ioas->mutex);
+
+		/*
+		 * TODO: Iterate over each device of this iommufd and only save
+		 * hwpt/domain if the device is persisted.
+		 */
+		list_for_each_entry(hwpt_paging, &ioas->hwpt_list, hwpt_item) {
+			if (!hwpt_paging->common.domain)
+				continue;
+
+			rc = iommu_domain_preserve(hwpt_paging->common.domain);
+			if (rc)
+				goto err;
+		}
+
+		mutex_unlock(&ioas->mutex);
+		ioas = NULL;
+	}
+
+	return 0;
+
+err:
+	if (ioas)
+		mutex_unlock(&ioas->mutex);
+	return rc;
+}
+
 static int iommufd_liveupdate_prepare(struct liveupdate_file_handler *handler,
 				      struct file *file, u64 *data)
 {
@@ -33,6 +76,10 @@ static int iommufd_liveupdate_prepare(struct liveupdate_file_handler *handler,
 
 	iommufd_lu = folio_address(folio_lu);
 
+	rc = iommufd_save_ioas(ictx, iommufd_lu);
+	if (rc)
+		goto err_folio_put;
+
 	rc = kho_preserve_folio(folio_lu);
 	if (rc)
 		goto err_folio_put;
-- 
2.51.0.536.g15c5d4f767-goog