Re: [PATCH v3 10/18] iommu/vt-d: Restore IOMMU state and reclaimed domain ids

[Samiullah Khawaja <skhawaja@google.com>]

On Mon, Jun 22, 2026 at 01:14:48PM +0800, Baolu Lu wrote:
>On 6/15/26 07:37, Samiullah Khawaja wrote:
>>During boot fetch the preserved state of IOMMU unit and if found then
>>restore the state.
>>
>>- Reuse the root_table that was preserved in the previous kernel.
>>- Reclaim the domain ids of the preserved domains for each preserved
>>   devices so these are not acquired by another domain.
>>
>>Signed-off-by: Samiullah Khawaja<skhawaja@google.com>
>>---
>>  drivers/iommu/intel/iommu.c      | 87 +++++++++++++++++++++++---------
>>  drivers/iommu/intel/iommu.h      |  7 +++
>>  drivers/iommu/intel/liveupdate.c | 60 ++++++++++++++++++++++
>>  3 files changed, 130 insertions(+), 24 deletions(-)
>>
>>diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>>index 26258861e3bf..cd40e274482b 100644
>>--- a/drivers/iommu/intel/iommu.c
>>+++ b/drivers/iommu/intel/iommu.c
>>@@ -990,15 +990,16 @@ static void disable_dmar_iommu(struct intel_iommu *iommu)
>>  		iommu_disable_translation(iommu);
>>  }
>>-static void free_dmar_iommu(struct intel_iommu *iommu)
>>+static void free_dmar_iommu(struct intel_iommu *iommu, struct iommu_hw_ser *iommu_ser)
>>  {
>>  	if (iommu->copied_tables) {
>>  		bitmap_free(iommu->copied_tables);
>>  		iommu->copied_tables = NULL;
>>  	}
>>-	/* free context mapping */
>>-	free_context_table(iommu);
>>+	/* free context mapping if there is no serialized state. */
>>+	if (!iommu_ser)
>>+		free_context_table(iommu);
>>  	if (ecap_prs(iommu->ecap))
>>  		intel_iommu_finish_prq(iommu);
>
>disable_dmar_iommu() and free_dmar_iommu() are always paired in the
>code. How about merging them into a single helper that is aware of iommu
>preservation? Something like the following?
>
>static void release_dmar_iommu(struct intel_iommu *iommu)
>{
>        struct iommu_hw_ser *iommu_ser =
>                        iommu_get_preserved_data(iommu->reg_phys, 
>IOMMU_INTEL);
>
>        /*
>         * All iommu domains must have been detached from the devices,
>         * hence there should be no domain IDs in use.
>         */
>        if (WARN_ON(!ida_is_empty(&iommu->domain_ida)))
>                return;
>
>        if ((iommu->gcmd & DMA_GCMD_TE) && !iommu_ser)
>                iommu_disable_translation(iommu);
>
>        if (iommu->copied_tables) {
>                bitmap_free(iommu->copied_tables);
>                iommu->copied_tables = NULL;
>        }
>
>        /* free context mapping if there is no serialized state. */
>        if (!iommu_ser)
>                free_context_table(iommu);
>
>        if (ecap_prs(iommu->ecap))
>                intel_iommu_finish_prq(iommu);
>}

This looks great. I will update this in v4.
>
>Thanks,
>baolu
>

Thanks,
Sami