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

[Ankit Soni]

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@xxxxxxxxxx>
> ---
>  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
>