Re: [PATCH v3 02/10] iommu/vt-d: Extend dmar_domain to support nested domain

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

On 5/24/23 3:02 PM, Tian, Kevin wrote:
>> From: Liu, Yi L<yi.l.liu@intel.com>
>> Sent: Thursday, May 11, 2023 10:51 PM
>>
>> From: Lu Baolu<baolu.lu@linux.intel.com>
>>
>> The nested domain fields are exclusive to those that used for a DMA
>> remapping domain. Use union to avoid memory waste.
>>
>> Signed-off-by: Lu Baolu<baolu.lu@linux.intel.com>
>> Signed-off-by: Yi Liu<yi.l.liu@intel.com>
>> ---
>>   drivers/iommu/intel/iommu.h | 35 +++++++++++++++++++++++++++++------
>>   1 file changed, 29 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
>> index 1c5e1d88862b..e818520f4068 100644
>> --- a/drivers/iommu/intel/iommu.h
>> +++ b/drivers/iommu/intel/iommu.h
>> @@ -596,15 +596,38 @@ struct dmar_domain {
>>   	spinlock_t lock;		/* Protect device tracking lists */
>>   	struct list_head devices;	/* all devices' list */
>>
>> -	struct dma_pte	*pgd;		/* virtual address */
>> -	int		gaw;		/* max guest address width */
>> -
>> -	/* adjusted guest address width, 0 is level 2 30-bit */
>> -	int		agaw;
>>   	int		iommu_superpage;/* Level of superpages supported:
>>   					   0 == 4KiB (no superpages), 1 ==
>> 2MiB,
>>   					   2 == 1GiB, 3 == 512GiB, 4 == 1TiB */
>> -	u64		max_addr;	/* maximum mapped address */
>> +	union {
>> +		/* DMA remapping domain */
>> +		struct {
>> +			/* virtual address */
>> +			struct dma_pte	*pgd;
>> +			/* max guest address width */
>> +			int		gaw;
>> +			/*
>> +			 * adjusted guest address width:
>> +			 *   0: level 2 30-bit
>> +			 *   1: level 3 39-bit
>> +			 *   2: level 4 48-bit
>> +			 *   3: level 5 57-bit
>> +			 */
>> +			int		agaw;
>> +			/* maximum mapped address */
>> +			u64		max_addr;
>> +		};
> what about 'nid'?


"nid" represents which NUMA node should we allocate pages from for this
domain. It's updated every time when a domain is attached/detached
to/from a device or pasid.

Generally speaking, "nid" is common for all types of domain. But in this
case, only a DMA remapping domain has a need to allocate pages. I intend
to keep it as it for now. There's more cleanup rooms if we limit it only
for DMA remapping domain.

Best regards,
baolu