linux-kernel - Re: [RFC PATCH 1/5] iommu: Add APIs for IOMMU PASID management

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Date:   Sun, 16 Dec 2018 09:20:38 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     "Liu, Yi L" <yi.l.liu@...el.com>, Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kirti Wankhede <kwankhede@...dia.com>
Cc:     baolu.lu@...ux.intel.com, "Raj, Ashok" <ashok.raj@...el.com>,
        "Kumar, Sanjay K" <sanjay.k.kumar@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        "Sun, Yi Y" <yi.y.sun@...el.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "Bie, Tiwei" <tiwei.bie@...el.com>,
        "Zeng, Xin" <xin.zeng@...el.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: Re: [RFC PATCH 1/5] iommu: Add APIs for IOMMU PASID management

Hi,

On 12/16/18 6:38 AM, Liu, Yi L wrote:
>> From: Lu Baolu [mailto:baolu.lu@...ux.intel.com]
>> Sent: Sunday, November 11, 2018 10:45 PM
>> Subject: [RFC PATCH 1/5] iommu: Add APIs for IOMMU PASID management
>>
>> This adds APIs for IOMMU drivers and device drivers to manage the PASIDs used for
>> DMA transfer and translation. It bases on I/O ASID allocator for PASID namespace
>> management and relies on vendor specific IOMMU drivers for paravirtual PASIDs.
>>
>> Below APIs are added:
>>
>> * iommu_pasid_init(pasid)
>>    - Initialize a PASID consumer. The vendor specific IOMMU
>>      drivers are able to set the PASID range imposed by IOMMU
>>      hardware through a callback in iommu_ops.
>>
>> * iommu_pasid_exit(pasid)
>>    - The PASID consumer stops consuming any PASID.
>>
>> * iommu_pasid_alloc(pasid, min, max, private, *ioasid)
>>    - Allocate a PASID and associate a @private data with this
>>      PASID. The PASID value is stored in @ioaisd if returning
>>      success.
>>
>> * iommu_pasid_free(pasid, ioasid)
>>    - Free a PASID to the pool so that it could be consumed by
>>      others.
>>
>> This also adds below helpers to lookup or iterate PASID items associated with a
>> consumer.
>>
>> * iommu_pasid_for_each(pasid, func, data)
>>    - Iterate PASID items of the consumer identified by @pasid,
>>      and call @func() against each item. An error returned from
>>      @func() will break the iteration.
>>
>> * iommu_pasid_find(pasid, ioasid)
>>    - Retrieve the private data associated with @ioasid.
>>
>> Cc: Ashok Raj <ashok.raj@...el.com>
>> Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
>> Cc: Kevin Tian <kevin.tian@...el.com>
>> Cc: Jean-Philippe Brucker <jean-philippe.brucker@....com>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>> ---
>>   drivers/iommu/Kconfig |  1 +
>>   drivers/iommu/iommu.c | 89 +++++++++++++++++++++++++++++++++++++++++++
>>   include/linux/iommu.h | 73 +++++++++++++++++++++++++++++++++++
>>   3 files changed, 163 insertions(+)
>>
>> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig index
>> d9a25715650e..39f2bb76c7b8 100644
>> --- a/drivers/iommu/Kconfig
>> +++ b/drivers/iommu/Kconfig
>> @@ -1,6 +1,7 @@
>>   # IOMMU_API always gets selected by whoever wants it.
>>   config IOMMU_API
>>   	bool
>> +	select IOASID
>>
>>   menuconfig IOMMU_SUPPORT
>>   	bool "IOMMU Hardware Support"
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index
>> 0b7c96d1425e..570b244897bb 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -2082,3 +2082,92 @@ void iommu_detach_device_aux(struct iommu_domain
>> *domain, struct device *dev)
>>   	}
>>   }
>>   EXPORT_SYMBOL_GPL(iommu_detach_device_aux);
>> +
>> +/*
>> + * APIs for PASID used by IOMMU and the device drivers which depend
>> + * on IOMMU.
>> + */
>> +struct iommu_pasid *iommu_pasid_init(struct bus_type *bus) {
> 
> I'm thinking about if using struct iommu_domain here is better
> than struct bus_type. The major purpose is to pass iommu_ops
> in it and route into iommu-sublayer. iommu_domain may be
> better since some modules like vfio_iommu_type1 would use
> iommu_domain more than bus type.

But drivers might call this during initialization when it doesn't has
any domain yet.

Best regards,
Lu Baolu