linux-kernel - Re: [PATCH v7 01/10] iommu: Add pasids field in struct iommu

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Message-ID: <3c112762-f6e6-0b41-b38f-3bb2995d97cf@linux.intel.com>
Date:   Wed, 25 May 2022 10:03:26 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Joerg Roedel <joro@...tes.org>,
        Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        "Raj, Ashok" <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        "Jiang, Dave" <dave.jiang@...el.com>, Vinod Koul <vkoul@...nel.org>
Cc:     baolu.lu@...ux.intel.com, Eric Auger <eric.auger@...hat.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>
Subject: Re: [PATCH v7 01/10] iommu: Add pasids field in struct iommu_device

Hi Kevin,

Thank you for reviewing my patches.

On 2022/5/24 17:24, Tian, Kevin wrote:
>> From: Lu Baolu <baolu.lu@...ux.intel.com>
>> Sent: Thursday, May 19, 2022 3:21 PM
>>
>> Use this field to keep the number of supported PASIDs that an IOMMU
>> hardware is able to support. This is a generic attribute of an IOMMU
>> and lifting it into the per-IOMMU device structure makes it possible
>> to allocate a PASID for device without calls into the IOMMU drivers.
>> Any iommu driver which suports PASID related features should set this
>> field before enabling them on the devices.
>>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>> Reviewed-by: Jean-Philippe Brucker <jean-philippe@...aro.org>
>> ---
>>   include/linux/iommu.h                       | 2 ++
>>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 1 +
>>   drivers/iommu/intel/dmar.c                  | 4 ++++
>>   3 files changed, 7 insertions(+)
>>
>> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
>> index 5e1afe169549..da423e87f248 100644
>> --- a/include/linux/iommu.h
>> +++ b/include/linux/iommu.h
>> @@ -318,12 +318,14 @@ struct iommu_domain_ops {
>>    * @list: Used by the iommu-core to keep a list of registered iommus
>>    * @ops: iommu-ops for talking to this iommu
>>    * @dev: struct device for sysfs handling
>> + * @pasids: number of supported PASIDs
>>    */
>>   struct iommu_device {
>>   	struct list_head list;
>>   	const struct iommu_ops *ops;
>>   	struct fwnode_handle *fwnode;
>>   	struct device *dev;
>> +	u32 pasids;
> 
> max_pasid or nr_pasids?

max_pasid looks better.

> 
>>   };
>>
>>   /**
>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> index 88817a3376ef..6e2cd082c670 100644
>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> @@ -3546,6 +3546,7 @@ static int arm_smmu_device_hw_probe(struct
>> arm_smmu_device *smmu)
>>   	/* SID/SSID sizes */
>>   	smmu->ssid_bits = FIELD_GET(IDR1_SSIDSIZE, reg);
>>   	smmu->sid_bits = FIELD_GET(IDR1_SIDSIZE, reg);
>> +	smmu->iommu.pasids = smmu->ssid_bits;
>>
>>   	/*
>>   	 * If the SMMU supports fewer bits than would fill a single L2 stream
>> diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
>> index 4de960834a1b..1c3cf267934d 100644
>> --- a/drivers/iommu/intel/dmar.c
>> +++ b/drivers/iommu/intel/dmar.c
>> @@ -1126,6 +1126,10 @@ static int alloc_iommu(struct dmar_drhd_unit
>> *drhd)
>>
>>   	raw_spin_lock_init(&iommu->register_lock);
>>
>> +	/* Supports full 20-bit PASID in scalable mode. */
>> +	if (ecap_pasid(iommu->ecap))
>> +		iommu->iommu.pasids = 1UL << 20;
>> +
> 
> supported pasid bits is reported by ecap_pss(). I don't think we should
> assume 20bits here.

Yes. I overlooked this. Thanks for reminding.

Another thing I need to improve is that scalable mode could be disabled.
This field should be 0 in that case.

> 
>>   	/*
>>   	 * This is only for hotplug; at boot time intel_iommu_enabled won't
>>   	 * be set yet. When intel_iommu_init() runs, it registers the units
>> --
>> 2.25.1
> 

Best regards,
baolu