Re: [PATCH 07/14] iommu/vt-d: Restore IOMMU state and reclaimed domain ids

[Vipin Sharma <vipinsh@google.com>]

On Tue, Feb 03, 2026 at 10:09:41PM +0000, 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.

Can this be two patches? One just restoring root table and second one to
reclaim device ids.

> -static void init_translation_status(struct intel_iommu *iommu)
> +static void init_translation_status(struct intel_iommu *iommu, bool restoring)
>  {
>  	u32 gsts;
>  
>  	gsts = readl(iommu->reg + DMAR_GSTS_REG);
> -	if (gsts & DMA_GSTS_TES)
> +	if (!restoring && (gsts & DMA_GSTS_TES))
>  		iommu->flags |= VTD_FLAG_TRANS_PRE_ENABLED;
>  }

I think we can just check in the caller, init_dmars(), and not call this
function. We are already modifying that function, so no need to make
changes here as well. WDYT?

>  
> @@ -670,10 +670,16 @@ void dmar_fault_dump_ptes(struct intel_iommu *iommu, u16 source_id,
>  #endif
>  
>  /* iommu handling */
> -static int iommu_alloc_root_entry(struct intel_iommu *iommu)
> +static int iommu_alloc_root_entry(struct intel_iommu *iommu, struct iommu_ser *restored_state)

Nit: Since we are using iommu_ser at other places, I will recommend to
keep it same variable name here as well.

> @@ -1636,8 +1643,10 @@ static int __init init_dmars(void)
>  						   intel_pasid_max_id);
>  		}
>  
> +		iommu_ser = iommu_get_preserved_data(iommu->reg_phys, IOMMU_INTEL);
> +
>  		intel_iommu_init_qi(iommu);
> -		init_translation_status(iommu);
> +		init_translation_status(iommu, !!iommu_ser);

Just put 'if' here to avoid changes in init_translation_status().

> +static int __restore_used_domain_ids(struct device_ser *ser, void *arg)

Nit: Just curious, why two __?

> +{
> +	int id = ser->domain_iommu_ser.did;
> +	struct intel_iommu *iommu = arg;
> +
> +	ida_alloc_range(&iommu->domain_ida, id, id, GFP_ATOMIC);

Should we check if allocation succeeded or not?

> +	return 0;
> +}
> +
> +void intel_iommu_liveupdate_restore_root_table(struct intel_iommu *iommu,
> +					       struct iommu_ser *iommu_ser)
> +{
> +	BUG_ON(!kho_restore_folio(iommu_ser->intel.root_table));
> +	iommu->root_entry = __va(iommu_ser->intel.root_table);
> +
> +	restore_iommu_context(iommu);
> +	iommu_for_each_preserved_device(__restore_used_domain_ids, iommu);
> +	pr_info("Restored IOMMU[0x%llx] Root Table at: 0x%llx\n",
> +		iommu->reg_phys, iommu_ser->intel.root_table);

Should raw pointer values be printed like this?