linux-kernel - Re: [PATCH v3 02/10] iommu/vt-d: Extend dmar

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Date:   Fri, 26 May 2023 10:56:02 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "jgg@...dia.com" <jgg@...dia.com>,
        "robin.murphy@....com" <robin.murphy@....com>
Cc:     baolu.lu@...ux.intel.com, "cohuck@...hat.com" <cohuck@...hat.com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "nicolinc@...dia.com" <nicolinc@...dia.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "mjrosato@...ux.ibm.com" <mjrosato@...ux.ibm.com>,
        "chao.p.peng@...ux.intel.com" <chao.p.peng@...ux.intel.com>,
        "yi.y.sun@...ux.intel.com" <yi.y.sun@...ux.intel.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        "lulu@...hat.com" <lulu@...hat.com>,
        "suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "Duan, Zhenzhong" <zhenzhong.duan@...el.com>
Subject: Re: [PATCH v3 02/10] iommu/vt-d: Extend dmar_domain to support nested
 domain

On 5/24/23 3:02 PM, Tian, Kevin wrote:
>> From: Liu, Yi L<yi.l.liu@...el.com>
>> Sent: Thursday, May 11, 2023 10:51 PM
>>
>> From: Lu Baolu<baolu.lu@...ux.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@...ux.intel.com>
>> Signed-off-by: Yi Liu<yi.l.liu@...el.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