Re: [PATCH v2 10/16] iommu: Restore and reattach preserved domains to devices

[Samiullah Khawaja <skhawaja@google.com>]

On Fri, May 29, 2026 at 04:43:42PM +0000, Ankit Soni wrote:
>On Mon, Apr 27, 2026 at 05:56:27PM +0000, Samiullah Khawaja wrote:
>> Restore the preserved domains by restoring the page tables using restore
>> IOMMU domain op. Reattach the preserved domain to the device during
>> default domain setup. While attaching, reuse the domain ID that was used
>> in the previous kernel. The context entry setup is not needed as that is
>> preserved during liveupdate.
>>
>> Signed-off-by: Samiullah Khawaja <skhawaja@google.com>
>> ---
>>  drivers/iommu/intel/iommu.c      | 49 ++++++++++++++------
>>  drivers/iommu/intel/iommu.h      |  3 +-
>>  drivers/iommu/intel/nested.c     |  2 +-
>>  drivers/iommu/iommu.c            | 61 ++++++++++++++++++++++++-
>>  drivers/iommu/liveupdate.c       | 78 ++++++++++++++++++++++++++++++++
>>  include/linux/iommu-liveupdate.h | 50 ++++++++++++++++++++
>>  6 files changed, 224 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>> index 4118a0861f38..b90757164cd8 100644
>> --- a/drivers/iommu/intel/iommu.c
>> +++ b/drivers/iommu/intel/iommu.c
>> @@ -1031,7 +1031,8 @@ static bool first_level_by_default(struct intel_iommu *iommu)
>>  	return true;
>>  }
>>
>> -int domain_attach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu)
>> +int domain_attach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu,
>> +			int restore_did)
>>  {
>>  	struct iommu_domain_info *info, *curr;
>>  	int num, ret = -ENOSPC;
>> @@ -1051,8 +1052,11 @@ int domain_attach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu)
>>  		return 0;
>>  	}
>>
>> -	num = ida_alloc_range(&iommu->domain_ida, IDA_START_DID,
>> -			      cap_ndoms(iommu->cap) - 1, GFP_KERNEL);
>> +	if (restore_did >= IDA_START_DID)
>> +		num = restore_did;
>> +	else
>> +		num = ida_alloc_range(&iommu->domain_ida, IDA_START_DID,
>> +				      cap_ndoms(iommu->cap) - 1, GFP_KERNEL);
>>  	if (num < 0) {
>>  		pr_err("%s: No free domain ids\n", iommu->name);
>>  		goto err_unlock;
>> @@ -1320,10 +1324,14 @@ static int dmar_domain_attach_device(struct dmar_domain *domain,
>>  {
>>  	struct device_domain_info *info = dev_iommu_priv_get(dev);
>>  	struct intel_iommu *iommu = info->iommu;
>> +	struct device_ser *device_ser = NULL;
>
>Typo here? iommu_device_ser.
>compiles because dev_iommu_restored_state() returns void * and the
>variable is only null-checked, never dereferenced.

Agreed. Will update this.
>
>Ankit
>
>>  	unsigned long flags;
>>  	int ret;
>>
>> -	ret = domain_attach_iommu(domain, iommu);
>> +	device_ser = dev_iommu_restored_state(dev);
>> +
>> +	ret = domain_attach_iommu(domain, iommu,
>> +				  dev_iommu_restore_did(dev, &domain->domain));
>>  	if (ret)
>>  		return ret;
>>

[snip]
>>  static inline struct iommu_hw_ser *iommu_get_preserved_data(u64 token, enum iommu_type_ser type)
>>  {
>>  	return NULL;
>> --
>> 2.54.0.545.g6539524ca2-goog
>>

Thanks,
Sami