Re: [PATCH v4 6/8] vfio/mdev: Add iommu place holders in mdev_device

[Kirti Wankhede <kwankhede@nvidia.com>]

On 11/7/2018 7:18 AM, Lu Baolu wrote:
> Hi Alex,
> 
> On 11/7/18 7:53 AM, Alex Williamson wrote:
>> On Mon,  5 Nov 2018 15:34:06 +0800
>> Lu Baolu <baolu.lu@linux.intel.com> wrote:
>>
>>> A parent device might create different types of mediated
>>> devices. For example, a mediated device could be created
>>> by the parent device with full isolation and protection
>>> provided by the IOMMU. One usage case could be found on
>>> Intel platforms where a mediated device is an assignable
>>> subset of a PCI, the DMA requests on behalf of it are all
>>> tagged with a PASID. Since IOMMU supports PASID-granular
>>> translations (scalable mode in vt-d 3.0), this mediated
>>> device could be individually protected and isolated by an
>>> IOMMU.
>>>
>>> This patch adds two new members in struct mdev_device:
>>> * iommu_device
>>>    - This, if set, indicates that the mediated device could
>>>      be fully isolated and protected by IOMMU via attaching
>>>      an iommu domain to this device. If empty, it indicates
>>>      using vendor defined isolation.
>>>
>>> * iommu_domain
>>>    - This is a place holder for an iommu domain. A domain
>>>      could be store here for later use once it has been
>>>      attached to the iommu_device of this mdev.
>>>
>>> Below helpers are added to set and get above iommu device
>>> and iommu domain pointers.
>>>
>>> * mdev_set/get_iommu_device(dev, iommu_device)
>>>    - Set or get the iommu device which represents this mdev
>>>      in IOMMU's device scope. Drivers don't need to set the
>>>      iommu device if it uses vendor defined isolation.
>>>
>>> * mdev_set/get_iommu_domain(domain)
>>>    - A iommu domain which has been attached to the iommu
>>>      device in order to protect and isolate the mediated
>>>      device will be kept in the mdev data structure and
>>>      could be retrieved later.
>>>
>>> Cc: Ashok Raj <ashok.raj@intel.com>
>>> Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
>>> Cc: Kevin Tian <kevin.tian@intel.com>
>>> Cc: Liu Yi L <yi.l.liu@intel.com>
>>> Suggested-by: Kevin Tian <kevin.tian@intel.com>
>>> Suggested-by: Alex Williamson <alex.williamson@redhat.com>
>>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>>> ---
>>>   drivers/vfio/mdev/mdev_core.c    | 36 ++++++++++++++++++++++++++++++++
>>>   drivers/vfio/mdev/mdev_private.h |  2 ++
>>>   include/linux/mdev.h             | 23 ++++++++++++++++++++
>>>   3 files changed, 61 insertions(+)
>>>
>>> diff --git a/drivers/vfio/mdev/mdev_core.c
>>> b/drivers/vfio/mdev/mdev_core.c
>>> index 0212f0ee8aea..5119809225c5 100644
>>> --- a/drivers/vfio/mdev/mdev_core.c
>>> +++ b/drivers/vfio/mdev/mdev_core.c
>>> @@ -390,6 +390,42 @@ int mdev_device_remove(struct device *dev, bool
>>> force_remove)
>>>       return 0;
>>>   }
>>>   +int mdev_set_iommu_device(struct device *dev, struct device
>>> *iommu_device)
>>> +{
>>> +    struct mdev_device *mdev = to_mdev_device(dev);
>>> +
>>> +    mdev->iommu_device = iommu_device;
>>> +
>>> +    return 0;
>>> +}
>>> +EXPORT_SYMBOL(mdev_set_iommu_device);
>>> +
>>> +struct device *mdev_get_iommu_device(struct device *dev)
>>> +{
>>> +    struct mdev_device *mdev = to_mdev_device(dev);
>>> +
>>> +    return mdev->iommu_device;
>>> +}
>>> +EXPORT_SYMBOL(mdev_get_iommu_device);
>>> +
>>> +int mdev_set_iommu_domain(struct device *dev, void *domain)
>>> +{
>>> +    struct mdev_device *mdev = to_mdev_device(dev);
>>> +
>>> +    mdev->iommu_domain = domain;
>>> +
>>> +    return 0;
>>> +}
>>> +EXPORT_SYMBOL(mdev_set_iommu_domain);
>>> +
>>> +void *mdev_get_iommu_domain(struct device *dev)
>>> +{
>>> +    struct mdev_device *mdev = to_mdev_device(dev);
>>> +
>>> +    return mdev->iommu_domain;
>>> +}
>>> +EXPORT_SYMBOL(mdev_get_iommu_domain);
>>> +
>>>   static int __init mdev_init(void)
>>>   {
>>>       return mdev_bus_register();
>>> diff --git a/drivers/vfio/mdev/mdev_private.h
>>> b/drivers/vfio/mdev/mdev_private.h
>>> index b5819b7d7ef7..c01518068e84 100644
>>> --- a/drivers/vfio/mdev/mdev_private.h
>>> +++ b/drivers/vfio/mdev/mdev_private.h
>>> @@ -34,6 +34,8 @@ struct mdev_device {
>>>       struct list_head next;
>>>       struct kobject *type_kobj;
>>>       bool active;
>>> +    struct device *iommu_device;
>>> +    void *iommu_domain;
>>>   };
>>>     #define to_mdev_device(dev)    container_of(dev, struct
>>> mdev_device, dev)
>>> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
>>> index b6e048e1045f..c46777d3e568 100644
>>> --- a/include/linux/mdev.h
>>> +++ b/include/linux/mdev.h
>>> @@ -14,6 +14,29 @@
>>>   #define MDEV_H
>>>     struct mdev_device;
>>> +struct iommu_domain;
>>> +
>>> +/*
>>> + * Called by the parent device driver to set the PCI device which
>>> represents
>>
>> s/PCI //
>>
>> There is no requirement or expectation that the device is PCI.
>>
> 
> Fair enough.
> 
>>> + * this mdev in iommu protection scope. By default, the iommu device
>>> is NULL,
>>> + * that indicates using vendor defined isolation.
>>> + *
>>> + * @dev: the mediated device that iommu will isolate.
>>> + * @iommu_device: a pci device which represents the iommu for @dev.
>>> + *
>>> + * Return 0 for success, otherwise negative error value.
>>> + */
>>> +int mdev_set_iommu_device(struct device *dev, struct device
>>> *iommu_device);
>>> +
>>> +struct device *mdev_get_iommu_device(struct device *dev);
>>> +
>>> +/*
>>> + * Called by vfio iommu modules to save the iommu domain after a
>>> domain being
>>> + * attached to the mediated device.
>>> + */
>>> +int mdev_set_iommu_domain(struct device *dev, void *domain);
>>> +
>>> +void *mdev_get_iommu_domain(struct device *dev);
>>
>> I can't say I really understand the purpose of this, the cover letter
>> indicates this is a placeholder, should we add it separately when we
>> have a requirement for it?
> 
> Oh, I am sorry that I used a wrong word. It's not a placeholder for
> something designed for future, but adding two members that will be used
> in the following patches. Since they will be used in anther modules
> (like vfio_iommu), we need function interfaces to get and set them.
> 
> mdev->iommu_device:
>  -  This, if set, indicates that the mediated device could
>     be fully isolated and protected by IOMMU via attaching
>     an iommu domain to this device. If empty, it indicates
>     using vendor defined isolation.
> 
> mdev->iommu_domain:
>   - This is used to save the pointer of an iommu domain. Once
>     a domain has been attached to the iommu_device, it should
>     be stored here.
> 

I don't see mdev->iommu_domain is used anywhere in this series of patch.
If this is not being used, then no need to save it. With that symbols
mdev_set/get_iommu_domain(domain) are not required.

Please keep symbols mdev_set/get_iommu_device(dev, iommu_device) non-GPL
same as other exported symbols from mdev_core module.

Thanks,
Kirti