linux-kernel - Re: [PATCH RFC 06/11] iommu/sva: Use attach/detach_pasid

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Date:   Tue, 22 Mar 2022 12:29:40 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc:     baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
        Jason Gunthorpe <jgg@...dia.com>,
        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 06/11] iommu/sva: Use attach/detach_pasid_dev in SVA
 interfaces

On 2022/3/21 19:33, Jean-Philippe Brucker wrote:
> On Sun, Mar 20, 2022 at 02:40:25PM +0800, Lu Baolu wrote:
>> diff --git a/drivers/iommu/iommu-sva-lib.c b/drivers/iommu/iommu-sva-lib.c
>> index 106506143896..47cf98e661ff 100644
>> --- a/drivers/iommu/iommu-sva-lib.c
>> +++ b/drivers/iommu/iommu-sva-lib.c
>> @@ -3,6 +3,8 @@
>>    * Helpers for IOMMU drivers implementing SVA
>>    */
>>   #include <linux/mutex.h>
>> +#include <linux/iommu.h>
>> +#include <linux/slab.h>
>>   #include <linux/sched/mm.h>
>>   
>>   #include "iommu-sva-lib.h"
>> @@ -69,3 +71,101 @@ struct mm_struct *iommu_sva_find(ioasid_t pasid)
>>   	return ioasid_find(&iommu_sva_pasid, pasid, __mmget_not_zero);
>>   }
>>   EXPORT_SYMBOL_GPL(iommu_sva_find);
>> +
>> +static struct iommu_domain *iommu_sva_domain_alloc(struct device *dev)
>> +{
>> +	struct bus_type *bus = dev->bus;
>> +	struct iommu_domain *domain;
>> +
>> +	if (!bus || !bus->iommu_ops)
>> +		return NULL;
>> +
>> +	domain = bus->iommu_ops->domain_alloc(IOMMU_DOMAIN_SVA);
>> +	if (domain)
>> +		domain->type = IOMMU_DOMAIN_SVA;
>> +
>> +	return domain;
>> +}
>> +
>> +/**
>> + * iommu_sva_bind_device() - Bind a process address space to a device
>> + * @dev: the device
>> + * @mm: the mm to bind, caller must hold a reference to it
>> + * @drvdata: opaque data pointer to pass to bind callback
>> + *
>> + * Create a bond between device and address space, allowing the device to access
>> + * the mm using the returned PASID. If a bond already exists between @device and
>> + * @mm, it is returned and an additional reference is taken.
> This is not true anymore, we return a different structure for each call.
> 
>> Caller must call
>> + * iommu_sva_unbind_device() to release each reference.
>> + *
>> + * iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) must be called first, to
>> + * initialize the required SVA features.
>> + *
>> + * On error, returns an ERR_PTR value.
>> + */
>> +struct iommu_sva *
>> +iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void *drvdata)
>> +{
>> +	int ret = -EINVAL;
>> +	struct iommu_sva *handle;
>> +	struct iommu_domain *domain;
>> +
>> +	handle = kzalloc(sizeof(*handle), GFP_KERNEL);
>> +	if (!handle)
>> +		return ERR_PTR(-ENOMEM);
>> +
>> +	ret = iommu_sva_alloc_pasid(mm, 1, (1U << dev->iommu->pasid_bits) - 1);
>> +	if (ret)
>> +		goto out;
>> +
>> +	domain = iommu_sva_domain_alloc(dev);
>> +	if (!domain) {
>> +		ret = -ENOMEM;
>> +		goto out;
>> +	}
>> +	domain->sva_cookie = mm;
>> +
>> +	ret = iommu_attach_device_pasid(domain, dev, mm->pasid);
>> +	if (ret)
>> +		goto out_free_domain;
>> +
>> +	handle->dev = dev;
>> +	handle->domain = domain;
>> +	handle->pasid = mm->pasid;
>> +
>> +	return handle;
>> +
>> +out_free_domain:
>> +	iommu_domain_free(domain);
>> +out:
>> +	kfree(handle);
>> +
>> +	return ERR_PTR(ret);
>> +}
>> +EXPORT_SYMBOL_GPL(iommu_sva_bind_device);
>> +
>> +/**
>> + * iommu_sva_unbind_device() - Remove a bond created with iommu_sva_bind_device
>> + * @handle: the handle returned by iommu_sva_bind_device()
>> + *
>> + * Put reference to a bond between device and address space.
> Same here. But I'd prefer keeping the old behavior so device drivers don't
> have to keep track of {dev, mm} pairs themselves.

Okay. Thank you for pointing this out. Let me figure it out in the next
version.

Best regards,
baolu