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

[Lu Baolu <baolu.lu@linux.intel.com>]

Hi,

On 11/16/18 5:31 AM, Kirti Wankhede wrote:
> 
> 
> 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.

Yes. We won't use mdev->iommu_domain in this patch series. It should be
used by mdev parent driver to retrieve the default pasid of the domain.
Something like:

domain = mdev_get_iommu_domain(dev)
pasid = iommu_domain_get_attr(domain, DOMAIN_ATTR_AUXD_ID);
reg_write(pasid_reg, pasid);

I am okay if we remove mdev_set/get_iommu_domain from this patch series
and add it later when the parent driver comes.

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

Yes. It will be fixed in the next version.

> 
> Thanks,
> Kirti
> 

Best regards,
Lu Baolu