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

[Baolu Lu <baolu.lu@linux.intel.com>]

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);
}

Thanks,
baolu