Re: [PATCH 04/14] iommu/pages: Add APIs to preserve/unpreserve/restore iommu pages

Ankit Soni
2026-03-03T16:42:23Z

On Tue, Feb 03, 2026 at 10:09:38PM +0000, Samiullah Khawaja wrote:
> 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@google.com>
> ---
> drivers/iommu/iommu-pages.c | 74 +++++++++++++++++++++++++++++++++++++
> drivers/iommu/iommu-pages.h | 30 +++++++++++++++
> 2 files changed, 104 insertions(+)
>
> diff --git a/drivers/iommu/iommu-pages.c b/drivers/iommu/iommu-pages.c
> index 3bab175d8557..588a8f19b196 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 +132,79 @@ void iommu_put_pages_list(struct iommu_pages_list *list)
> }
> EXPORT_SYMBOL_GPL(iommu_put_pages_list);
>
> +#if IS_ENABLED(CONFIG_IOMMU_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)
> + return;
> +
> + /* If less than zero then unpreserve all pages. */
> + 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);

iopt->incoherent = false; should be here?

> +
> + 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..bd336fb56b5f 100644
> --- a/drivers/iommu/iommu-pages.h
> +++ b/drivers/iommu/iommu-pages.h
> @@ -53,6 +53,36 @@ 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_IOMMU_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);
> +#else
> +static inline int iommu_preserve_page(void *virt)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> +static inline void iommu_unpreserve_page(void *virt)
> +{
> +}
> +
> +static inline int iommu_preserve_pages(struct iommu_pages_list *list)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> +static inline void iommu_unpreserve_pages(struct iommu_pages_list *list, int count)
> +{
> +}
> +
> +static inline 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
> --
> 2.53.0.rc2.204.g2597b5adb4-goog
>