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

Sorry for the confusion.

Best regards,
Lu Baolu

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