linux-kernel - [RFC PATCH v2 11/32] iommu/pages: Add APIs to preserve/unpreserve/restore iommu pages

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Message-ID: <20251202230303.1017519-12-skhawaja@google.com>
Date: Tue,  2 Dec 2025 23:02:41 +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 11/32] iommu/pages: Add APIs to preserve/unpreserve/restore
 iommu pages

IOMMU pages are allocated/freed using APIs using struct ioptdesc. For
the proper preservation and restoration of ioptdesc add helper
functions.

Signed-off-by: Samiullah Khawaja <skhawaja@...gle.com>
---
 drivers/iommu/iommu-pages.c | 70 +++++++++++++++++++++++++++++++++++++
 drivers/iommu/iommu-pages.h |  8 +++++
 2 files changed, 78 insertions(+)

diff --git a/drivers/iommu/iommu-pages.c b/drivers/iommu/iommu-pages.c
index 3bab175d8557..14669b0f498f 100644
--- a/drivers/iommu/iommu-pages.c
+++ b/drivers/iommu/iommu-pages.c
@@ -6,6 +6,7 @@
 #include "iommu-pages.h"
 #include <linux/dma-mapping.h>
 #include <linux/gfp.h>
+#include <linux/kexec_handover.h>
 #include <linux/mm.h>
 
 #define IOPTDESC_MATCH(pg_elm, elm)                    \
@@ -131,6 +132,75 @@ void iommu_put_pages_list(struct iommu_pages_list *list)
 }
 EXPORT_SYMBOL_GPL(iommu_put_pages_list);
 
+#if IS_ENABLED(CONFIG_LIVEUPDATE)
+void iommu_unpreserve_page(void *virt)
+{
+	kho_unpreserve_folio(ioptdesc_folio(virt_to_ioptdesc(virt)));
+}
+EXPORT_SYMBOL_GPL(iommu_unpreserve_page);
+
+int iommu_preserve_page(void *virt)
+{
+	return kho_preserve_folio(ioptdesc_folio(virt_to_ioptdesc(virt)));
+}
+EXPORT_SYMBOL_GPL(iommu_preserve_page);
+
+void iommu_unpreserve_pages(struct iommu_pages_list *list, int count)
+{
+	struct ioptdesc *iopt;
+
+	if (count < 0)
+		count = 0;
+
+	list_for_each_entry(iopt, &list->pages, iopt_freelist_elm) {
+		kho_unpreserve_folio(ioptdesc_folio(iopt));
+		if (count > 0 && --count ==  0)
+			break;
+	}
+}
+EXPORT_SYMBOL_GPL(iommu_unpreserve_pages);
+
+void iommu_restore_page(u64 phys)
+{
+	struct ioptdesc *iopt;
+	struct folio *folio;
+	unsigned long pgcnt;
+	unsigned int order;
+
+	folio = kho_restore_folio(phys);
+	BUG_ON(!folio);
+
+	iopt = folio_ioptdesc(folio);
+
+	order = folio_order(folio);
+	pgcnt = 1UL << order;
+	mod_node_page_state(folio_pgdat(folio), NR_IOMMU_PAGES, pgcnt);
+	lruvec_stat_mod_folio(folio, NR_SECONDARY_PAGETABLE, pgcnt);
+}
+EXPORT_SYMBOL_GPL(iommu_restore_page);
+
+int iommu_preserve_pages(struct iommu_pages_list *list)
+{
+	struct ioptdesc *iopt;
+	int count = 0;
+	int ret;
+
+	list_for_each_entry(iopt, &list->pages, iopt_freelist_elm) {
+		ret = kho_preserve_folio(ioptdesc_folio(iopt));
+		if (ret) {
+			iommu_unpreserve_pages(list, count);
+			return ret;
+		}
+
+		++count;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(iommu_preserve_pages);
+
+#endif
+
 /**
  * iommu_pages_start_incoherent - Setup the page for cache incoherent operation
  * @virt: The page to setup
diff --git a/drivers/iommu/iommu-pages.h b/drivers/iommu/iommu-pages.h
index ae9da4f571f6..ec1787776edd 100644
--- a/drivers/iommu/iommu-pages.h
+++ b/drivers/iommu/iommu-pages.h
@@ -53,6 +53,14 @@ void *iommu_alloc_pages_node_sz(int nid, gfp_t gfp, size_t size);
 void iommu_free_pages(void *virt);
 void iommu_put_pages_list(struct iommu_pages_list *list);
 
+#if IS_ENABLED(CONFIG_LIVEUPDATE)
+int iommu_preserve_page(void *virt);
+void iommu_unpreserve_page(void *virt);
+int iommu_preserve_pages(struct iommu_pages_list *list);
+void iommu_unpreserve_pages(struct iommu_pages_list *list, int count);
+void iommu_restore_page(u64 phys);
+#endif
+
 /**
  * iommu_pages_list_add - add the page to a iommu_pages_list
  * @list: List to add the page to
-- 
2.52.0.158.g65b55ccf14-goog