linux-kernel - Re: [PATCH RFC v2 06/11] iommu/vt-d: Add SVA domain support

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Date:   Mon, 4 Apr 2022 14:52:24 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v2 06/11] iommu/vt-d: Add SVA domain support

On 2022/3/31 3:09, Jason Gunthorpe wrote:
> On Tue, Mar 29, 2022 at 01:37:55PM +0800, Lu Baolu wrote:
>> Add support for SVA domain allocation and provide an SVA-specific
>> iommu_domain_ops.
>>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>>   include/linux/intel-iommu.h |  1 +
>>   drivers/iommu/intel/iommu.c | 10 ++++++++++
>>   drivers/iommu/intel/svm.c   | 37 +++++++++++++++++++++++++++++++++++++
>>   3 files changed, 48 insertions(+)
>>
>> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
>> index 2f9891cb3d00..c14283137fb5 100644
>> +++ b/include/linux/intel-iommu.h
>> @@ -744,6 +744,7 @@ void intel_svm_unbind(struct iommu_sva *handle);
>>   u32 intel_svm_get_pasid(struct iommu_sva *handle);
>>   int intel_svm_page_response(struct device *dev, struct iommu_fault_event *evt,
>>   			    struct iommu_page_response *msg);
>> +extern const struct iommu_domain_ops intel_svm_domain_ops;
>>   
>>   struct intel_svm_dev {
>>   	struct list_head list;
>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>> index c1b91bce1530..5eae7cf9bee5 100644
>> +++ b/drivers/iommu/intel/iommu.c
>> @@ -4318,6 +4318,16 @@ static struct iommu_domain *intel_iommu_domain_alloc(unsigned type)
>>   		return domain;
>>   	case IOMMU_DOMAIN_IDENTITY:
>>   		return &si_domain->domain;
>> +#ifdef CONFIG_INTEL_IOMMU_SVM
>> +	case IOMMU_DOMAIN_SVA:
>> +		dmar_domain = alloc_domain(type);
>> +		if (!dmar_domain)
>> +			return NULL;
>> +		domain = &dmar_domain->domain;
>> +		domain->ops = &intel_svm_domain_ops;
>> +
>> +		return domain;
>> +#endif /* CONFIG_INTEL_IOMMU_SVM */
> 
> If this is the usual pattern for drivers I would prefer to see an
> alloc_sva op instead of more and more types.
> 
> Multiplexing functions is often not a great idea...

Robin mentioned that the iommu domain alloc/free interfaces are under
reforming. These cleanups need to wait to see what the final code looks
like.

Best regards,
baolu