Re: [PATCH v6 02/18] iommu/pages: Add APIs to preserve/unpreserve/restore iommu pages

[Samiullah Khawaja <skhawaja@google.com>]

On Fri, Oct 30, 2026 at 09:26:45AM +0800, Baolu Lu wrote:
>On 10/25/2026 10:19 AM, Samiullah Khawaja wrote:
>>IOMMU pages are allocated/freed using APIs using struct ioptdesc. For
>>the proper preservation and restoration of ioptdesc add helper
>>functions.
>>
>>Reviewed-by: Pranjal Shrivastava<praan@google.com>
>>Signed-off-by: Samiullah Khawaja<skhawaja@google.com>
>>---
>>  drivers/iommu/iommu-pages.c | 109 ++++++++++++++++++++++++++++++++++--
>>  drivers/iommu/iommu-pages.h |  30 ++++++++++
>>  2 files changed, 135 insertions(+), 4 deletions(-)
>>
>
>[...]
>
>>+
>>+/**
>>+ * iommu_restore_pages - Restore pages that were preserved in KHO
>>+ * @phys: Physical address of page to restore
>>+ */
>>+void iommu_restore_pages(u64 phys)
>>+{
>>+	struct ioptdesc *iopt;
>>+	struct folio *folio;
>>+	unsigned long pgcnt;
>>+	unsigned int order;
>>+
>>+	folio = kho_restore_folio(phys);
>>+	if (!folio)
>>+		panic("Failed to restore preserved IOMMU page %llx\n", phys);
>>+
>>+	iopt = folio_ioptdesc(folio);
>>+
>>+	/*
>>+	 * For the restored pages incoherent is set to false as these are not
>>+	 * mapped using the DMA_API. The remapping of these pages using DMA_API
>>+	 * is not needed as these are not going to be written to by the new
>>+	 * kernel.
>>+	 */
>>+	iopt->incoherent = false;
>>+
>>+	order = folio_order(folio);
>>+	pgcnt = 1UL << order;
>>+	iommu_folio_update_stats(folio, pgcnt);
>>+}
>>+EXPORT_SYMBOL_GPL(iommu_restore_pages);
>
>The pages were charged to the VMM's memcg in the old kernel (iommufd
>maps with GFP_KERNEL_ACCOUNT), but after the live update they are no
>longer charged to any memcg. I think that's fine, because the restored
>tables are immutable and will be replaced by ordinary ones after boot.
>
>This patch looks good to me,
>
>Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>

Thanks for the review,
Sami