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From: Lu Baolu <baolu.lu@linux.intel.com>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: baolu.lu@linux.intel.com, Joerg Roedel <joro@8bytes.org>,
	Alex Williamson <alex.williamson@redhat.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	Kevin Tian <kevin.tian@intel.com>,
	Dave Jiang <dave.jiang@intel.com>,
	Ashok Raj <ashok.raj@intel.com>,
	kvm@vger.kernel.org, Cornelia Huck <cohuck@redhat.com>,
	linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
	Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v3 2/4] iommu: Add iommu_aux_at(de)tach_group()
Date: Thu, 16 Jul 2020 09:07:46 +0800
Message-ID: <435a2014-c2e8-06b9-3c9a-4afbf6607ffe@linux.intel.com> (raw)
In-Reply-To: <20200715090114.50a459d4@jacob-builder>

Hi Jacob,

On 7/16/20 12:01 AM, Jacob Pan wrote:
> On Wed, 15 Jul 2020 08:47:36 +0800
> Lu Baolu <baolu.lu@linux.intel.com> wrote:
> 
>> Hi Jacob,
>>
>> On 7/15/20 12:39 AM, Jacob Pan wrote:
>>> On Tue, 14 Jul 2020 13:57:01 +0800
>>> Lu Baolu<baolu.lu@linux.intel.com>  wrote:
>>>    
>>>> This adds two new aux-domain APIs for a use case like vfio/mdev
>>>> where sub-devices derived from an aux-domain capable device are
>>>> created and put in an iommu_group.
>>>>
>>>> /**
>>>>    * iommu_aux_attach_group - attach an aux-domain to an iommu_group
>>>> which
>>>>    *                          contains sub-devices (for example
>>>> mdevs) derived
>>>>    *                          from @dev.
>>>>    * @domain: an aux-domain;
>>>>    * @group:  an iommu_group which contains sub-devices derived from
>>>> @dev;
>>>>    * @dev:    the physical device which supports IOMMU_DEV_FEAT_AUX.
>>>>    *
>>>>    * Returns 0 on success, or an error value.
>>>>    */
>>>> int iommu_aux_attach_group(struct iommu_domain *domain,
>>>>                              struct iommu_group *group,
>>>>                              struct device *dev)
>>>>
>>>> /**
>>>>    * iommu_aux_detach_group - detach an aux-domain from an
>>>> iommu_group *
>>>>    * @domain: an aux-domain;
>>>>    * @group:  an iommu_group which contains sub-devices derived from
>>>> @dev;
>>>>    * @dev:    the physical device which supports IOMMU_DEV_FEAT_AUX.
>>>>    *
>>>>    * @domain must have been attached to @group via
>>>> iommu_aux_attach_group(). */
>>>> void iommu_aux_detach_group(struct iommu_domain *domain,
>>>>                               struct iommu_group *group,
>>>>                               struct device *dev)
>>>>
>>>> It also adds a flag in the iommu_group data structure to identify
>>>> an iommu_group with aux-domain attached from those normal ones.
>>>>
>>>> Signed-off-by: Lu Baolu<baolu.lu@linux.intel.com>
>>>> ---
>>>>    drivers/iommu/iommu.c | 58
>>>> +++++++++++++++++++++++++++++++++++++++++++ include/linux/iommu.h |
>>>> 17 +++++++++++++ 2 files changed, 75 insertions(+)
>>>>
>>>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>>>> index e1fdd3531d65..cad5a19ebf22 100644
>>>> --- a/drivers/iommu/iommu.c
>>>> +++ b/drivers/iommu/iommu.c
>>>> @@ -45,6 +45,7 @@ struct iommu_group {
>>>>    	struct iommu_domain *default_domain;
>>>>    	struct iommu_domain *domain;
>>>>    	struct list_head entry;
>>>> +	unsigned int aux_domain_attached:1;
>>>>    };
>>>>    
>>>>    struct group_device {
>>>> @@ -2759,6 +2760,63 @@ int iommu_aux_get_pasid(struct iommu_domain
>>>> *domain, struct device *dev) }
>>>>    EXPORT_SYMBOL_GPL(iommu_aux_get_pasid);
>>>>    
>>>> +/**
>>>> + * iommu_aux_attach_group - attach an aux-domain to an iommu_group
>>>> which
>>>> + *                          contains sub-devices (for example
>>>> mdevs) derived
>>>> + *                          from @dev.
>>>> + * @domain: an aux-domain;
>>>> + * @group:  an iommu_group which contains sub-devices derived from
>>>> @dev;
>>>> + * @dev:    the physical device which supports IOMMU_DEV_FEAT_AUX.
>>>> + *
>>>> + * Returns 0 on success, or an error value.
>>>> + */
>>>> +int iommu_aux_attach_group(struct iommu_domain *domain,
>>>> +			   struct iommu_group *group, struct
>>>> device *dev) +{
>>>> +	int ret = -EBUSY;
>>>> +
>>>> +	mutex_lock(&group->mutex);
>>>> +	if (group->domain)
>>>> +		goto out_unlock;
>>>> +
>>> Perhaps I missed something but are we assuming only one mdev per
>>> mdev group? That seems to change the logic where vfio does:
>>> iommu_group_for_each_dev()
>>> 	iommu_aux_attach_device()
>>>    
>>
>> It has been changed in PATCH 4/4:
>>
>> static int vfio_iommu_attach_group(struct vfio_domain *domain,
>>                                      struct vfio_group *group)
>> {
>>           if (group->mdev_group)
>>                   return iommu_aux_attach_group(domain->domain,
>>                                                 group->iommu_group,
>>                                                 group->iommu_device);
>>           else
>>                   return iommu_attach_group(domain->domain,
>> group->iommu_group);
>> }
>>
>> So, for both normal domain and aux-domain, we use the same concept:
>> attach a domain to a group.
>>
> I get that, but don't you have to attach all the devices within the

This iommu_group includes only mediated devices derived from an
IOMMU_DEV_FEAT_AUX-capable device. Different from iommu_attach_group(),
iommu_aux_attach_group() doesn't need to attach the domain to each
device in group, instead it only needs to attach the domain to the
physical device where the mdev's were created from.

> group? Here you see the group already has a domain and exit.

If the (group->domain) has been set, that means a domain has already
attached to the group, so it returns -EBUSY.

Best regards,
baolu

  reply index

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-14  5:56 [PATCH v3 0/4] iommu aux-domain APIs extensions Lu Baolu
2020-07-14  5:57 ` [PATCH v3 1/4] iommu: Check IOMMU_DEV_FEAT_AUX feature in aux api's Lu Baolu
2020-07-29 20:03   ` Alex Williamson
2020-07-30  1:46     ` Lu Baolu
2020-07-14  5:57 ` [PATCH v3 2/4] iommu: Add iommu_aux_at(de)tach_group() Lu Baolu
2020-07-14 16:39   ` Jacob Pan
2020-07-15  0:47     ` Lu Baolu
2020-07-15 16:01       ` Jacob Pan
2020-07-16  1:07         ` Lu Baolu [this message]
2020-07-29 20:03           ` Alex Williamson
2020-07-29 23:34             ` Tian, Kevin
2020-07-30 19:46               ` Alex Williamson
2020-07-31  5:47                 ` Lu Baolu
2020-07-31 18:05                   ` Alex Williamson
2020-08-03  1:57                     ` Lu Baolu
2020-07-14  5:57 ` [PATCH v3 3/4] iommu: Add iommu_aux_get_domain_for_dev() Lu Baolu
2020-07-29 20:25   ` Alex Williamson
2020-07-29 23:49     ` Tian, Kevin
2020-07-30 20:17       ` Alex Williamson
2020-07-31  0:26         ` Tian, Kevin
2020-07-31  2:17         ` Tian, Kevin
2020-07-31  6:30     ` Lu Baolu
2020-07-31 18:14       ` Alex Williamson
2020-08-03  2:15         ` Lu Baolu
2020-07-14  5:57 ` [PATCH v3 4/4] vfio/type1: Use iommu_aux_at(de)tach_group() APIs Lu Baolu
2020-07-14  8:25   ` Christoph Hellwig
2020-07-14 16:29     ` Jacob Pan
2020-07-15  1:00       ` Lu Baolu
2020-07-15  1:23         ` Tian, Kevin
2020-07-29 20:32   ` Alex Williamson
2020-07-30  2:41     ` Lu Baolu
2020-07-30 21:17       ` Alex Williamson
2020-07-31  1:37         ` Lu Baolu
2020-07-30  9:36   ` Liu, Yi L
2020-07-31  1:39     ` Lu Baolu
2020-07-23 13:55 ` [PATCH v3 0/4] iommu aux-domain APIs extensions Lu Baolu

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