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Date: Mon, 14 Sep 2020 11:02:24 +0800
From: Lu Baolu <baolu.lu@...ux.intel.com>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
Robin Murphy <robin.murphy@....com>,
Jean-Philippe Brucker <jean-philippe@...aro.org>,
Cornelia Huck <cohuck@...hat.com>,
Kevin Tian <kevin.tian@...el.com>,
Ashok Raj <ashok.raj@...el.com>,
Dave Jiang <dave.jiang@...el.com>,
Liu Yi L <yi.l.liu@...el.com>, Zeng Xin <xin.zeng@...el.com>,
iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org
Subject: Re: [PATCH v4 2/5] iommu: Add iommu_at(de)tach_subdev_group()
Hi Alex,
On 9/11/20 6:05 AM, Alex Williamson wrote:
> On Tue, 1 Sep 2020 11:34:19 +0800
> Lu Baolu <baolu.lu@...ux.intel.com> wrote:
>
>> This adds two new APIs for the use cases like vfio/mdev where subdevices
>> derived from physical devices are created and put in an iommu_group. The
>> new IOMMU API interfaces mimic the vfio_mdev_at(de)tach_domain() directly,
>> testing whether the resulting device supports IOMMU_DEV_FEAT_AUX and using
>> an aux vs non-aux at(de)tach.
>>
>> By doing this we could
>>
>> - Set the iommu_group.domain. The iommu_group.domain is private to iommu
>> core (therefore vfio code cannot set it), but we need it set in order
>> for iommu_get_domain_for_dev() to work with a group attached to an aux
>> domain.
>>
>> - Prefer to use the _attach_group() interfaces while the _attach_device()
>> interfaces are relegated to special cases.
>>
>> Link: https://lore.kernel.org/linux-iommu/20200730134658.44c57a67@x1.home/
>> Link: https://lore.kernel.org/linux-iommu/20200730151703.5daf8ad4@x1.home/
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>> ---
>> drivers/iommu/iommu.c | 136 ++++++++++++++++++++++++++++++++++++++++++
>> include/linux/iommu.h | 20 +++++++
>> 2 files changed, 156 insertions(+)
>>
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index 38cdfeb887e1..fb21c2ff4861 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -2757,6 +2757,142 @@ int iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev)
>> }
>> EXPORT_SYMBOL_GPL(iommu_aux_get_pasid);
>>
>> +static int __iommu_aux_attach_device(struct iommu_domain *domain,
>> + struct device *phys_dev,
>> + struct device *sub_dev)
>> +{
>> + int ret;
>> +
>> + if (unlikely(!domain->ops->aux_attach_dev))
>> + return -ENODEV;
>> +
>> + ret = domain->ops->aux_attach_dev(domain, phys_dev, sub_dev);
>> + if (!ret)
>> + trace_attach_device_to_domain(sub_dev);
>> +
>> + return ret;
>> +}
>> +
>> +static void __iommu_aux_detach_device(struct iommu_domain *domain,
>> + struct device *phys_dev,
>> + struct device *sub_dev)
>> +{
>> + if (unlikely(!domain->ops->aux_detach_dev))
>> + return;
>> +
>> + domain->ops->aux_detach_dev(domain, phys_dev, sub_dev);
>> + trace_detach_device_from_domain(sub_dev);
>> +}
>> +
>> +static int __iommu_attach_subdev_group(struct iommu_domain *domain,
>> + struct iommu_group *group,
>> + iommu_device_lookup_t fn)
>> +{
>> + struct group_device *device;
>> + struct device *phys_dev;
>> + int ret = -ENODEV;
>> +
>> + list_for_each_entry(device, &group->devices, list) {
>> + phys_dev = fn(device->dev);
>> + if (!phys_dev) {
>> + ret = -ENODEV;
>> + break;
>> + }
>> +
>> + if (iommu_dev_feature_enabled(phys_dev, IOMMU_DEV_FEAT_AUX))
>> + ret = __iommu_aux_attach_device(domain, phys_dev,
>> + device->dev);
>> + else
>> + ret = __iommu_attach_device(domain, phys_dev);
>> +
>> + if (ret)
>> + break;
>> + }
>> +
>> + return ret;
>> +}
>> +
>> +static void __iommu_detach_subdev_group(struct iommu_domain *domain,
>> + struct iommu_group *group,
>> + iommu_device_lookup_t fn)
>> +{
>> + struct group_device *device;
>> + struct device *phys_dev;
>> +
>> + list_for_each_entry(device, &group->devices, list) {
>> + phys_dev = fn(device->dev);
>> + if (!phys_dev)
>> + break;
>
>
> Seems like this should be a continue rather than a break. On the
> unwind path maybe we're relying on holding the group mutex and
> deterministic behavior from the fn() callback to unwind to the same
> point, but we still have an entirely separate detach interface and I'm
> not sure we couldn't end up with an inconsistent state if we don't
> iterate each group device here. Thanks,
Yes, agreed.
Best regards,
baolu
>
> Alex
>
>> +
>> + if (iommu_dev_feature_enabled(phys_dev, IOMMU_DEV_FEAT_AUX))
>> + __iommu_aux_detach_device(domain, phys_dev, device->dev);
>> + else
>> + __iommu_detach_device(domain, phys_dev);
>> + }
>> +}
>> +
>> +/**
>> + * iommu_attach_subdev_group - attach domain to an iommu_group which
>> + * contains subdevices.
>> + *
>> + * @domain: domain
>> + * @group: iommu_group which contains subdevices
>> + * @fn: callback for each subdevice in the @iommu_group to retrieve the
>> + * physical device where the subdevice was created from.
>> + *
>> + * Returns 0 on success, or an error value.
>> + */
>> +int iommu_attach_subdev_group(struct iommu_domain *domain,
>> + struct iommu_group *group,
>> + iommu_device_lookup_t fn)
>> +{
>> + int ret = -ENODEV;
>> +
>> + mutex_lock(&group->mutex);
>> + if (group->domain) {
>> + ret = -EBUSY;
>> + goto unlock_out;
>> + }
>> +
>> + ret = __iommu_attach_subdev_group(domain, group, fn);
>> + if (ret)
>> + __iommu_detach_subdev_group(domain, group, fn);
>> + else
>> + group->domain = domain;
>> +
>> +unlock_out:
>> + mutex_unlock(&group->mutex);
>> + return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(iommu_attach_subdev_group);
>> +
>> +/**
>> + * iommu_detach_subdev_group - detach domain from an iommu_group which
>> + * contains subdevices
>> + *
>> + * @domain: domain
>> + * @group: iommu_group which contains subdevices
>> + * @fn: callback for each subdevice in the @iommu_group to retrieve the
>> + * physical device where the subdevice was created from.
>> + *
>> + * The domain must have been attached to @group via iommu_attach_subdev_group().
>> + */
>> +void iommu_detach_subdev_group(struct iommu_domain *domain,
>> + struct iommu_group *group,
>> + iommu_device_lookup_t fn)
>> +{
>> + mutex_lock(&group->mutex);
>> + if (!group->domain)
>> + goto unlock_out;
>> +
>> + __iommu_detach_subdev_group(domain, group, fn);
>> + group->domain = NULL;
>> +
>> +unlock_out:
>> + mutex_unlock(&group->mutex);
>> +}
>> +EXPORT_SYMBOL_GPL(iommu_detach_subdev_group);
>> +
>> /**
>> * iommu_sva_bind_device() - Bind a process address space to a device
>> * @dev: the device
>> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
>> index 871267104915..b9df8b510d4f 100644
>> --- a/include/linux/iommu.h
>> +++ b/include/linux/iommu.h
>> @@ -48,6 +48,7 @@ struct iommu_fault_event;
>> typedef int (*iommu_fault_handler_t)(struct iommu_domain *,
>> struct device *, unsigned long, int, void *);
>> typedef int (*iommu_dev_fault_handler_t)(struct iommu_fault *, void *);
>> +typedef struct device *(*iommu_device_lookup_t)(struct device *);
>>
>> struct iommu_domain_geometry {
>> dma_addr_t aperture_start; /* First address that can be mapped */
>> @@ -631,6 +632,12 @@ bool iommu_dev_feature_enabled(struct device *dev, enum iommu_dev_features f);
>> int iommu_aux_attach_device(struct iommu_domain *domain, struct device *dev);
>> void iommu_aux_detach_device(struct iommu_domain *domain, struct device *dev);
>> int iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev);
>> +int iommu_attach_subdev_group(struct iommu_domain *domain,
>> + struct iommu_group *group,
>> + iommu_device_lookup_t fn);
>> +void iommu_detach_subdev_group(struct iommu_domain *domain,
>> + struct iommu_group *group,
>> + iommu_device_lookup_t fn);
>>
>> struct iommu_sva *iommu_sva_bind_device(struct device *dev,
>> struct mm_struct *mm,
>> @@ -1019,6 +1026,19 @@ iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev)
>> return -ENODEV;
>> }
>>
>> +static inline int
>> +iommu_attach_subdev_group(struct iommu_domain *domain, struct iommu_group *group,
>> + iommu_device_lookup_t fn)
>> +{
>> + return -ENODEV;
>> +}
>> +
>> +static inline void
>> +iommu_detach_subdev_group(struct iommu_domain *domain, struct iommu_group *group,
>> + iommu_device_lookup_t fn)
>> +{
>> +}
>> +
>> static inline struct iommu_sva *
>> iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void *drvdata)
>> {
>
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