[PATCH v3 0/8] vfio/mdev: IOMMU aware mediated device

[PATCH v3 0/8] vfio/mdev: IOMMU aware mediated device

[Lu Baolu]

Hi,

The Mediate Device is a framework for fine-grained physical device
sharing across the isolated domains. Currently the mdev framework
is designed to be independent of the platform IOMMU support. As the
result, the DMA isolation relies on the mdev parent device in a
vendor specific way.

There are several cases where a mediated device could be protected
and isolated by the platform IOMMU. For example, Intel vt-d rev3.0
[1] introduces a new translation mode called 'scalable mode', which
enables PASID-granular translations. The vt-d scalable mode is the
key ingredient for Scalable I/O Virtualization [2] [3] which allows
sharing a device in minimal possible granularity (ADI - Assignable
Device Interface).

A mediated device backed by an ADI could be protected and isolated
by the IOMMU since 1) the parent device supports tagging an unique
PASID to all DMA traffic out of the mediated device; and 2) the DMA
translation unit (IOMMU) supports the PASID granular translation.
We can apply IOMMU protection and isolation to this kind of devices
just as what we are doing with an assignable PCI device.

In order to distinguish the IOMMU-capable mediated devices from those
which still need to rely on parent devices, this patch set 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 in mdev core implementation.

* 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.

The mdev parent device driver could opt-in that the mdev could be
fully isolated and protected by the IOMMU when the mdev is being
created by invoking mdev_set_iommu_device() in its @create().

In the vfio_iommu_type1_attach_group(), a domain allocated through
iommu_domain_alloc() will be attached to the mdev iommu device if
an iommu device has been set. Otherwise, the dummy external domain
will be used and all the DMA isolation and protection are routed to
parent driver as the result.

On IOMMU side, a basic requirement is allowing to attach multiple
domains to a PCI device if the device advertises the capability
and the IOMMU hardware supports finer granularity translations than
the normal PCI Source ID based translation.

As the result, a PCI device could work in two modes: normal mode
and auxiliary mode. In the normal mode, a pci device could be
isolated in the Source ID granularity; the pci device itself could
be assigned to a user application by attaching a single domain
to it. In the auxiliary mode, a pci device could be isolated in
finer granularity, hence subsets of the device could be assigned
to different user level application by attaching a different domain
to each subset.

The device driver is able to switch between above two modes with
below interfaces:

* iommu_get_dev_attr(dev, IOMMU_DEV_ATTR_AUXD_CAPABILITY)
  - Represents the ability of supporting multiple domains
    per device.

* iommu_set_dev_attr(dev, IOMMU_DEV_ATTR_AUXD_ENABLE)
  - Enable the multiple domains capability for the device
    referenced by @dev.

* iommu_set_dev_attr(dev, IOMMU_DEV_ATTR_AUXD_DISABLE)
  - Disable the multiple domains capability for the device
    referenced by @dev.

* iommu_domain_get_attr(domain, DOMAIN_ATTR_AUXD_ID)
  - Return ID used for finer-granularity DMA translation.

The existing interfaces for attaching/detaching domains keep the
same as before. The different behaviors between the normal mode
and the auxiliary mode are handled in the vendor specific iommu
drivers.

In order for the ease of discussion, sometimes we call "a domain in
auxiliary mode' or simply 'an auxiliary domain' when a domain is
attached to a device for finer granularity translations. But we need
to keep in mind that this doesn't mean there is a differnt domain
type. A same domain could be bound to a device for Source ID based
translation, and bound to another device for finer granularity
translation at the same time.

This patch series extends both IOMMU and vfio components to support
mdev device passing through when it could be isolated and protected
by the IOMMU units. The first part of this series (PATCH 1/08~5/08)
adds the interfaces and implementation of the multiple domains per
device. The second part (PATCH 6/08~8/08) adds the iommu device
attribute to each mdev, determines isolation type according to the
existence of an iommu device when attaching group in vfio type1 iommu
module, and attaches the domain to iommu aware mediated devices.

This patch series depends on a patch set posted here [4] for discussion
which added scalable mode support in Intel IOMMU driver.

References:
[1] https://software.intel.com/en-us/download/intel-virtualization-technology-for-directed-io-architecture-specification
[2] https://software.intel.com/en-us/download/intel-scalable-io-virtualization-technical-specification
[3] https://schd.ws/hosted_files/lc32018/00/LC3-SIOV-final.pdf
[4] https://lkml.org/lkml/2018/10/7/54

Best regards,
Lu Baolu

Change log:
  v2->v3:
  - Remove domain type enum and use a pointer on mdev_device instead.
  - Add a generic interface for getting/setting per device iommu
    attributions. And use it for query aux domain capability, enable
    aux domain and disable aux domain purpose.
  - Reuse iommu_domain_get_attr() to retrieve the id in a aux domain.
  - We discussed the impact of the default domain implementation
    on reusing iommu_at(de)tach_device() interfaces. We agreed
    that reusing iommu_at(de)tach_device() interfaces is the right
    direction and we could tweak the code to remove the impact.
    https://www.spinics.net/lists/kvm/msg175285.html  
  - Removed the RFC tag since no objections received.
  - This patch has been submitted separately.
    https://www.spinics.net/lists/kvm/msg173936.html

  v1->v2:
  - Rewrite the patches with the concept of auxiliary domains.

Lu Baolu (8):
  iommu: Add APIs for multiple domains per device
  iommu/vt-d: Add multiple domains per device query
  iommu/vt-d: Enable/disable multiple domains per device
  iommu/vt-d: Attach/detach domains in auxiliary mode
  iommu/vt-d: Return ID associated with an auxiliary domain
  vfio/mdev: Add iommu place holders in mdev_device
  vfio/type1: Add domain at(de)taching group helpers
  vfio/type1: Handle different mdev isolation type

 drivers/iommu/intel-iommu.c      | 249 ++++++++++++++++++++++++++++++-
 drivers/iommu/iommu.c            |  25 ++++
 drivers/vfio/mdev/mdev_core.c    |  36 +++++
 drivers/vfio/mdev/mdev_private.h |   2 +
 drivers/vfio/vfio_iommu_type1.c  | 146 ++++++++++++++++--
 include/linux/intel-iommu.h      |  11 ++
 include/linux/iommu.h            |  33 ++++
 include/linux/mdev.h             |  23 +++
 8 files changed, 509 insertions(+), 16 deletions(-)

-- 
2.17.1

[PATCH v3 1/8] iommu: Add APIs for multiple domains per device

[Lu Baolu]

Sharing a physical PCI device in a finer-granularity way
is becoming a consensus in the industry. IOMMU vendors
are also engaging efforts to support such sharing as well
as possible. Among the efforts, the capability of support
finer-granularity DMA isolation is a common requirement
due to the security consideration. With finer-granularity
DMA isolation, all DMA requests out of or to a subset of
a physical PCI device can be protected by the IOMMU. As a
result, there is a request in software to attach multiple
domains to a physical PCI device. One example of such use
model is the Intel Scalable IOV [1] [2]. The Intel vt-d
3.0 spec [3] introduces the scalable mode which enables
PASID granularity DMA isolation.

This adds the APIs to support multiple domains per device.
In order to ease the discussions, we call it 'a domain in
auxiliary mode' or simply 'auxiliary domain' when multiple
domains are attached to a physical device.

The APIs includes:

* iommu_get_dev_attr(dev, IOMMU_DEV_ATTR_AUXD_CAPABILITY)
  - Represents the ability of supporting multiple domains
    per device.

* iommu_set_dev_attr(dev, IOMMU_DEV_ATTR_AUXD_ENABLE)
  - Enable the multiple domains capability for the device
    referenced by @dev.

* iommu_set_dev_attr(dev, IOMMU_DEV_ATTR_AUXD_DISABLE)
  - Disable the multiple domains capability for the device
    referenced by @dev.

* iommu_domain_get_attr(domain, DOMAIN_ATTR_AUXD_ID)
  - Return ID used for finer-granularity DMA translation.
    For the Intel Scalable IOV usage model, this will be
    a PASID. The device which supports Scalalbe IOV needs
    to writes this ID to the device register so that DMA
    requests could be tagged with a right PASID prefix.

Many people involved in discussions of this design.

Kevin Tian <kevin.tian@intel.com>
Liu Yi L <yi.l.liu@intel.com>
Ashok Raj <ashok.raj@intel.com>
Sanjay Kumar <sanjay.k.kumar@intel.com>
Jacob Pan <jacob.jun.pan@linux.intel.com>
Alex Williamson <alex.williamson@redhat.com>
Jean-Philippe Brucker <jean-philippe.brucker@arm.com>

and some discussions can be found here [4].

[1] https://software.intel.com/en-us/download/intel-scalable-io-virtualization-technical-specification
[2] https://schd.ws/hosted_files/lc32018/00/LC3-SIOV-final.pdf
[3] https://software.intel.com/en-us/download/intel-virtualization-technology-for-directed-io-architecture-specification
[4] https://lkml.org/lkml/2018/7/26/4

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: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 drivers/iommu/iommu.c | 25 +++++++++++++++++++++++++
 include/linux/iommu.h | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 8c15c5980299..d06cfdcf38a7 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2014,3 +2014,28 @@ int iommu_fwspec_add_ids(struct device *dev, u32 *ids, int num_ids)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(iommu_fwspec_add_ids);
+
+/*
+ * Generic interfaces to get or set per device IOMMU attributions.
+ */
+int iommu_get_dev_attr(struct device *dev, enum iommu_dev_attr attr, void *data)
+{
+	const struct iommu_ops *ops = dev->bus->iommu_ops;
+
+	if (ops && ops->get_dev_attr)
+		return ops->get_dev_attr(dev, attr, data);
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(iommu_get_dev_attr);
+
+int iommu_set_dev_attr(struct device *dev, enum iommu_dev_attr attr, void *data)
+{
+	const struct iommu_ops *ops = dev->bus->iommu_ops;
+
+	if (ops && ops->set_dev_attr)
+		return ops->set_dev_attr(dev, attr, data);
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(iommu_set_dev_attr);
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 87994c265bf5..0230b64cc6e9 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -125,6 +125,7 @@ enum iommu_attr {
 	DOMAIN_ATTR_FSL_PAMUV1,
 	DOMAIN_ATTR_NESTING,	/* two stages of translation */
 	DOMAIN_ATTR_MAX,
+	DOMAIN_ATTR_AUXD_ID,
 };
 
 /* These are the possible reserved region types */
@@ -155,6 +156,13 @@ struct iommu_resv_region {
 	enum iommu_resv_type	type;
 };
 
+/* Per device IOMMU attributions */
+enum iommu_dev_attr {
+	IOMMU_DEV_ATTR_AUXD_CAPABILITY,
+	IOMMU_DEV_ATTR_AUXD_ENABLE,
+	IOMMU_DEV_ATTR_AUXD_DISABLE,
+};
+
 #ifdef CONFIG_IOMMU_API
 
 /**
@@ -184,6 +192,8 @@ struct iommu_resv_region {
  * @domain_set_windows: Set the number of windows for a domain
  * @domain_get_windows: Return the number of windows for a domain
  * @of_xlate: add OF master IDs to iommu grouping
+ * @get_dev_attr: get per device IOMMU attributions
+ * @set_dev_attr: set per device IOMMU attributions
  * @pgsize_bitmap: bitmap of all possible supported page sizes
  */
 struct iommu_ops {
@@ -231,6 +241,12 @@ struct iommu_ops {
 	int (*of_xlate)(struct device *dev, struct of_phandle_args *args);
 	bool (*is_attach_deferred)(struct iommu_domain *domain, struct device *dev);
 
+	/* Get/set per device IOMMU attributions */
+	int (*get_dev_attr)(struct device *dev,
+			    enum iommu_dev_attr attr, void *data);
+	int (*set_dev_attr)(struct device *dev,
+			    enum iommu_dev_attr attr, void *data);
+
 	unsigned long pgsize_bitmap;
 };
 
@@ -400,6 +416,11 @@ void iommu_fwspec_free(struct device *dev);
 int iommu_fwspec_add_ids(struct device *dev, u32 *ids, int num_ids);
 const struct iommu_ops *iommu_ops_from_fwnode(struct fwnode_handle *fwnode);
 
+int iommu_get_dev_attr(struct device *dev,
+		       enum iommu_dev_attr attr, void *data);
+int iommu_set_dev_attr(struct device *dev,
+		       enum iommu_dev_attr attr, void *data);
+
 #else /* CONFIG_IOMMU_API */
 
 struct iommu_ops {};
@@ -684,6 +705,18 @@ const struct iommu_ops *iommu_ops_from_fwnode(struct fwnode_handle *fwnode)
 	return NULL;
 }
 
+static inline int
+iommu_get_dev_attr(struct device *dev, enum iommu_dev_attr attr, void *data)
+{
+	return -EINVAL;
+}
+
+static inline int
+iommu_set_dev_attr(struct device *dev, enum iommu_dev_attr attr, void *data)
+{
+	return -EINVAL;
+}
+
 #endif /* CONFIG_IOMMU_API */
 
 #ifdef CONFIG_IOMMU_DEBUGFS
-- 
2.17.1

[PATCH v3 2/8] iommu/vt-d: Add multiple domains per device query

[Lu Baolu]

Add the response to IOMMU_DEV_ATTR_AUXD_CAPABILITY capability query
through iommu_get_dev_attr().

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>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 drivers/iommu/intel-iommu.c | 38 +++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 4b1f7426acea..3133216e5733 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -5170,6 +5170,24 @@ static phys_addr_t intel_iommu_iova_to_phys(struct iommu_domain *domain,
 	return phys;
 }
 
+static inline bool scalable_mode_support(void)
+{
+	struct dmar_drhd_unit *drhd;
+	struct intel_iommu *iommu;
+	bool ret = true;
+
+	rcu_read_lock();
+	for_each_active_iommu(iommu, drhd) {
+		if (!sm_supported(iommu)) {
+			ret = false;
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	return ret;
+}
+
 static bool intel_iommu_capable(enum iommu_cap cap)
 {
 	if (cap == IOMMU_CAP_CACHE_COHERENCY)
@@ -5334,6 +5352,25 @@ struct intel_iommu *intel_svm_device_to_iommu(struct device *dev)
 }
 #endif /* CONFIG_INTEL_IOMMU_SVM */
 
+static int intel_iommu_get_dev_attr(struct device *dev,
+				    enum iommu_dev_attr attr, void *data)
+{
+	int ret = 0;
+	bool *auxd_capable;
+
+	switch (attr) {
+	case IOMMU_DEV_ATTR_AUXD_CAPABILITY:
+		auxd_capable = data;
+		*auxd_capable = scalable_mode_support();
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
 const struct iommu_ops intel_iommu_ops = {
 	.capable		= intel_iommu_capable,
 	.domain_alloc		= intel_iommu_domain_alloc,
@@ -5348,6 +5385,7 @@ const struct iommu_ops intel_iommu_ops = {
 	.get_resv_regions	= intel_iommu_get_resv_regions,
 	.put_resv_regions	= intel_iommu_put_resv_regions,
 	.device_group		= pci_device_group,
+	.get_dev_attr		= intel_iommu_get_dev_attr,
 	.pgsize_bitmap		= INTEL_IOMMU_PGSIZES,
 };
 
-- 
2.17.1

[PATCH v3 3/8] iommu/vt-d: Enable/disable multiple domains per device

[Lu Baolu]

Add iommu ops for enabling and disabling multiple domains per
device.

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>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 drivers/iommu/intel-iommu.c | 57 +++++++++++++++++++++++++++++++++++++
 include/linux/intel-iommu.h |  1 +
 2 files changed, 58 insertions(+)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 3133216e5733..27beda7f9d88 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -2476,6 +2476,7 @@ static struct dmar_domain *dmar_insert_one_dev_info(struct intel_iommu *iommu,
 	info->domain = domain;
 	info->iommu = iommu;
 	info->pasid_table = NULL;
+	info->auxd_enabled = 0;
 
 	if (dev && dev_is_pci(dev)) {
 		struct pci_dev *pdev = to_pci_dev(info->dev);
@@ -5371,6 +5372,61 @@ static int intel_iommu_get_dev_attr(struct device *dev,
 	return ret;
 }
 
+static int intel_iommu_enable_auxd(struct device *dev)
+{
+	struct device_domain_info *info;
+	struct dmar_domain *domain;
+	unsigned long flags;
+
+	if (!scalable_mode_support())
+		return -ENODEV;
+
+	domain = get_valid_domain_for_dev(dev);
+	if (!domain)
+		return -ENODEV;
+
+	spin_lock_irqsave(&device_domain_lock, flags);
+	info = dev->archdata.iommu;
+	info->auxd_enabled = 1;
+	spin_unlock_irqrestore(&device_domain_lock, flags);
+
+	return 0;
+}
+
+static int intel_iommu_disable_auxd(struct device *dev)
+{
+	struct device_domain_info *info;
+	unsigned long flags;
+
+	spin_lock_irqsave(&device_domain_lock, flags);
+	info = dev->archdata.iommu;
+	if (!WARN_ON(!info))
+		info->auxd_enabled = 0;
+	spin_unlock_irqrestore(&device_domain_lock, flags);
+
+	return 0;
+}
+
+static int intel_iommu_set_dev_attr(struct device *dev,
+				    enum iommu_dev_attr attr, void *data)
+{
+	int ret = 0;
+
+	switch (attr) {
+	case IOMMU_DEV_ATTR_AUXD_ENABLE:
+		ret = intel_iommu_enable_auxd(dev);
+		break;
+	case IOMMU_DEV_ATTR_AUXD_DISABLE:
+		ret = intel_iommu_disable_auxd(dev);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
 const struct iommu_ops intel_iommu_ops = {
 	.capable		= intel_iommu_capable,
 	.domain_alloc		= intel_iommu_domain_alloc,
@@ -5386,6 +5442,7 @@ const struct iommu_ops intel_iommu_ops = {
 	.put_resv_regions	= intel_iommu_put_resv_regions,
 	.device_group		= pci_device_group,
 	.get_dev_attr		= intel_iommu_get_dev_attr,
+	.set_dev_attr		= intel_iommu_set_dev_attr,
 	.pgsize_bitmap		= INTEL_IOMMU_PGSIZES,
 };
 
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index d174724e131f..6b198e13e75e 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -552,6 +552,7 @@ struct device_domain_info {
 	u8 pri_enabled:1;
 	u8 ats_supported:1;
 	u8 ats_enabled:1;
+	u8 auxd_enabled:1;	/* Multiple domains per device */
 	u8 ats_qdep;
 	struct device *dev; /* it's NULL for PCIe-to-PCI bridge */
 	struct intel_iommu *iommu; /* IOMMU used by this device */
-- 
2.17.1

[PATCH v3 4/8] iommu/vt-d: Attach/detach domains in auxiliary mode

[Lu Baolu]

When multiple domains per device has been enabled by the
device driver, the device will tag the default PASID for
the domain to all DMA traffics out of the subset of this
device; and the IOMMU should translate the DMA requests
in PASID granularity.

This extends the intel_iommu_attach/detach_device() ops
to support managing PASID granular translation structures
when the device driver has enabled multiple domains per
device.

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>
Signed-off-by: Sanjay Kumar <sanjay.k.kumar@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 drivers/iommu/intel-iommu.c | 132 +++++++++++++++++++++++++++++++++++-
 include/linux/intel-iommu.h |  10 +++
 2 files changed, 139 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 27beda7f9d88..3ca42b0e80df 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -2477,6 +2477,7 @@ static struct dmar_domain *dmar_insert_one_dev_info(struct intel_iommu *iommu,
 	info->iommu = iommu;
 	info->pasid_table = NULL;
 	info->auxd_enabled = 0;
+	INIT_LIST_HEAD(&info->auxiliary_domains);
 
 	if (dev && dev_is_pci(dev)) {
 		struct pci_dev *pdev = to_pci_dev(info->dev);
@@ -5013,6 +5014,124 @@ static void intel_iommu_domain_free(struct iommu_domain *domain)
 	domain_exit(to_dmar_domain(domain));
 }
 
+/*
+ * Check whether a @domain will be attached to the @dev in the
+ * auxiliary mode.
+ */
+static inline bool
+is_device_attach_aux_domain(struct device *dev, struct iommu_domain *domain)
+{
+	struct device_domain_info *info = dev->archdata.iommu;
+
+	return info && info->auxd_enabled &&
+			domain->type == IOMMU_DOMAIN_UNMANAGED;
+}
+
+static void auxiliary_link_device(struct dmar_domain *domain,
+				  struct device *dev)
+{
+	struct device_domain_info *info = dev->archdata.iommu;
+
+	assert_spin_locked(&device_domain_lock);
+	if (WARN_ON(!info))
+		return;
+
+	domain->auxd_refcnt++;
+	list_add(&domain->auxd, &info->auxiliary_domains);
+}
+
+static void auxiliary_unlink_device(struct dmar_domain *domain,
+				    struct device *dev)
+{
+	struct device_domain_info *info = dev->archdata.iommu;
+
+	assert_spin_locked(&device_domain_lock);
+	if (WARN_ON(!info))
+		return;
+
+	list_del(&domain->auxd);
+	domain->auxd_refcnt--;
+
+	if (!domain->auxd_refcnt && domain->default_pasid > 0)
+		intel_pasid_free_id(domain->default_pasid);
+}
+
+static int domain_add_dev_auxd(struct dmar_domain *domain,
+			       struct device *dev)
+{
+	int ret;
+	u8 bus, devfn;
+	unsigned long flags;
+	struct intel_iommu *iommu;
+
+	iommu = device_to_iommu(dev, &bus, &devfn);
+	if (!iommu)
+		return -ENODEV;
+
+	spin_lock_irqsave(&device_domain_lock, flags);
+	if (domain->default_pasid <= 0) {
+		domain->default_pasid = intel_pasid_alloc_id(domain, PASID_MIN,
+				intel_pasid_get_dev_max_id(dev), GFP_ATOMIC);
+		if (domain->default_pasid < 0) {
+			pr_err("Can't allocate default pasid\n");
+			ret = -ENODEV;
+			goto pasid_failed;
+		}
+	}
+
+	spin_lock(&iommu->lock);
+	ret = domain_attach_iommu(domain, iommu);
+	if (ret)
+		goto attach_failed;
+
+	/* Setup the PASID entry for mediated devices: */
+	ret = intel_pasid_setup_second_level(iommu, domain, dev,
+					     domain->default_pasid, false);
+	if (ret)
+		goto table_failed;
+	spin_unlock(&iommu->lock);
+
+	auxiliary_link_device(domain, dev);
+
+	spin_unlock_irqrestore(&device_domain_lock, flags);
+
+	return 0;
+
+table_failed:
+	domain_detach_iommu(domain, iommu);
+attach_failed:
+	spin_unlock(&iommu->lock);
+	if (!domain->auxd_refcnt && domain->default_pasid > 0)
+		intel_pasid_free_id(domain->default_pasid);
+pasid_failed:
+	spin_unlock_irqrestore(&device_domain_lock, flags);
+
+	return ret;
+}
+
+static void domain_remove_dev_aux(struct dmar_domain *domain,
+				  struct device *dev)
+{
+	struct device_domain_info *info;
+	struct intel_iommu *iommu;
+	unsigned long flags;
+
+	spin_lock_irqsave(&device_domain_lock, flags);
+	info = dev->archdata.iommu;
+	iommu = info->iommu;
+
+	intel_pasid_tear_down_second_level(iommu, domain,
+					   dev, domain->default_pasid);
+
+	auxiliary_unlink_device(domain, dev);
+
+	spin_lock(&iommu->lock);
+	domain_detach_iommu(domain, iommu);
+	spin_unlock(&iommu->lock);
+
+	spin_unlock_irqrestore(&device_domain_lock, flags);
+}
+
 static int intel_iommu_attach_device(struct iommu_domain *domain,
 				     struct device *dev)
 {
@@ -5027,7 +5146,8 @@ static int intel_iommu_attach_device(struct iommu_domain *domain,
 	}
 
 	/* normally dev is not mapped */
-	if (unlikely(domain_context_mapped(dev))) {
+	if (unlikely(domain_context_mapped(dev) &&
+		     !is_device_attach_aux_domain(dev, domain))) {
 		struct dmar_domain *old_domain;
 
 		old_domain = find_domain(dev);
@@ -5074,13 +5194,19 @@ static int intel_iommu_attach_device(struct iommu_domain *domain,
 		dmar_domain->agaw--;
 	}
 
-	return domain_add_dev_info(dmar_domain, dev);
+	if (is_device_attach_aux_domain(dev, domain))
+		return domain_add_dev_auxd(dmar_domain, dev);
+	else
+		return domain_add_dev_info(dmar_domain, dev);
 }
 
 static void intel_iommu_detach_device(struct iommu_domain *domain,
 				      struct device *dev)
 {
-	dmar_remove_one_dev_info(to_dmar_domain(domain), dev);
+	if (is_device_attach_aux_domain(dev, domain))
+		domain_remove_dev_aux(to_dmar_domain(domain), dev);
+	else
+		dmar_remove_one_dev_info(to_dmar_domain(domain), dev);
 }
 
 static int intel_iommu_map(struct iommu_domain *domain,
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index 6b198e13e75e..678c7fb05e74 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -473,9 +473,11 @@ struct dmar_domain {
 					/* Domain ids per IOMMU. Use u16 since
 					 * domain ids are 16 bit wide according
 					 * to VT-d spec, section 9.3 */
+	unsigned int	auxd_refcnt;	/* Refcount of auxiliary attaching */
 
 	bool has_iotlb_device;
 	struct list_head devices;	/* all devices' list */
+	struct list_head auxd;		/* link to device's auxiliary list */
 	struct iova_domain iovad;	/* iova's that belong to this domain */
 
 	struct dma_pte	*pgd;		/* virtual address */
@@ -494,6 +496,11 @@ struct dmar_domain {
 					   2 == 1GiB, 3 == 512GiB, 4 == 1TiB */
 	u64		max_addr;	/* maximum mapped address */
 
+	int		default_pasid;	/*
+					 * The default pasid used for non-SVM
+					 * traffic on mediated devices.
+					 */
+
 	struct iommu_domain domain;	/* generic domain data structure for
 					   iommu core */
 };
@@ -543,6 +550,9 @@ struct device_domain_info {
 	struct list_head link;	/* link to domain siblings */
 	struct list_head global; /* link to global list */
 	struct list_head table;	/* link to pasid table */
+	struct list_head auxiliary_domains; /* auxiliary domains
+					     * attached to this device
+					     */
 	u8 bus;			/* PCI bus number */
 	u8 devfn;		/* PCI devfn number */
 	u16 pfsid;		/* SRIOV physical function source ID */
-- 
2.17.1

[PATCH v3 5/8] iommu/vt-d: Return ID associated with an auxiliary domain

[Lu Baolu]

This adds support to return the default pasid associated with
an auxiliary domain. The PCI device which is bound with this
domain should use this value as the pasid for all DMA requests
of the subset of device which is isolated and protected with
this domain.

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>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 drivers/iommu/intel-iommu.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 3ca42b0e80df..4dc41232a0d6 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -5553,6 +5553,27 @@ static int intel_iommu_set_dev_attr(struct device *dev,
 	return ret;
 }
 
+static int intel_iommu_domain_get_attr(struct iommu_domain *domain,
+				       enum iommu_attr attr, void *data)
+{
+	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
+	int ret = -EINVAL, *id;
+
+	switch (attr) {
+	case DOMAIN_ATTR_AUXD_ID:
+		if (dmar_domain->default_pasid > 0) {
+			ret = 0;
+			id = data;
+			*id = dmar_domain->default_pasid;
+		}
+		break;
+	default:
+		break;
+	}
+
+	return ret;
+}
+
 const struct iommu_ops intel_iommu_ops = {
 	.capable		= intel_iommu_capable,
 	.domain_alloc		= intel_iommu_domain_alloc,
@@ -5567,6 +5588,7 @@ const struct iommu_ops intel_iommu_ops = {
 	.get_resv_regions	= intel_iommu_get_resv_regions,
 	.put_resv_regions	= intel_iommu_put_resv_regions,
 	.device_group		= pci_device_group,
+	.domain_get_attr	= intel_iommu_domain_get_attr,
 	.get_dev_attr		= intel_iommu_get_dev_attr,
 	.set_dev_attr		= intel_iommu_set_dev_attr,
 	.pgsize_bitmap		= INTEL_IOMMU_PGSIZES,
-- 
2.17.1

[PATCH v3 6/8] vfio/mdev: Add iommu place holders in mdev_device

[Lu Baolu]

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
+ * 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);
 
 /**
  * struct mdev_parent_ops - Structure to be registered for each parent device to
-- 
2.17.1

[PATCH v3 7/8] vfio/type1: Add domain at(de)taching group helpers

[Lu Baolu]

This adds helpers to attach or detach a domain to a
group. This will replace iommu_attach_group() which
only works for pci devices.

If a domain is attaching to a group which includes the
mediated devices, it should attach to the iommu device
(a pci device which represents the mdev in iommu scope)
instead. The added helper supports attaching domain to
groups for both pci and mdev devices.

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>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 drivers/vfio/vfio_iommu_type1.c | 98 ++++++++++++++++++++++++++++++---
 1 file changed, 91 insertions(+), 7 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index d9fd3188615d..3617499c95c9 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -91,6 +91,7 @@ struct vfio_dma {
 struct vfio_group {
 	struct iommu_group	*iommu_group;
 	struct list_head	next;
+	bool			mdev_group;	/* An mdev group */
 };
 
 /*
@@ -1327,6 +1328,89 @@ static bool vfio_iommu_has_sw_msi(struct iommu_group *group, phys_addr_t *base)
 	return ret;
 }
 
+static struct device *vfio_mdev_get_iommu_device(struct device *dev)
+{
+	struct device *(*fn)(struct device *dev);
+	struct device *iommu_parent;
+
+	fn = symbol_get(mdev_get_iommu_device);
+	if (fn) {
+		iommu_parent = fn(dev);
+		symbol_put(mdev_get_iommu_device);
+
+		return iommu_parent;
+	}
+
+	return NULL;
+}
+
+static int vfio_mdev_set_domain(struct device *dev, struct iommu_domain *domain)
+{
+	int (*fn)(struct device *dev, void *domain);
+	int ret;
+
+	fn = symbol_get(mdev_set_iommu_domain);
+	if (fn) {
+		ret = fn(dev, domain);
+		symbol_put(mdev_set_iommu_domain);
+
+		return ret;
+	}
+
+	return -EINVAL;
+}
+
+static int vfio_mdev_attach_domain(struct device *dev, void *data)
+{
+	struct iommu_domain *domain = data;
+	struct device *iommu_device;
+	int ret;
+
+	ret = vfio_mdev_set_domain(dev, domain);
+	if (ret)
+		return ret;
+
+	iommu_device = vfio_mdev_get_iommu_device(dev);
+	if (iommu_device)
+		return iommu_attach_device(domain, iommu_device);
+
+	return -EINVAL;
+}
+
+static int vfio_mdev_detach_domain(struct device *dev, void *data)
+{
+	struct iommu_domain *domain = data;
+	struct device *iommu_device;
+
+	vfio_mdev_set_domain(dev, NULL);
+	iommu_device = vfio_mdev_get_iommu_device(dev);
+	if (iommu_device)
+		iommu_detach_device(domain, iommu_device);
+
+	return 0;
+}
+
+static int vfio_iommu_attach_group(struct vfio_domain *domain,
+				   struct vfio_group *group)
+{
+	if (group->mdev_group)
+		return iommu_group_for_each_dev(group->iommu_group,
+						domain->domain,
+						vfio_mdev_attach_domain);
+	else
+		return iommu_attach_group(domain->domain, group->iommu_group);
+}
+
+static void vfio_iommu_detach_group(struct vfio_domain *domain,
+				    struct vfio_group *group)
+{
+	if (group->mdev_group)
+		iommu_group_for_each_dev(group->iommu_group, domain->domain,
+					 vfio_mdev_detach_domain);
+	else
+		iommu_detach_group(domain->domain, group->iommu_group);
+}
+
 static int vfio_iommu_type1_attach_group(void *iommu_data,
 					 struct iommu_group *iommu_group)
 {
@@ -1402,7 +1486,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 			goto out_domain;
 	}
 
-	ret = iommu_attach_group(domain->domain, iommu_group);
+	ret = vfio_iommu_attach_group(domain, group);
 	if (ret)
 		goto out_domain;
 
@@ -1434,8 +1518,8 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 	list_for_each_entry(d, &iommu->domain_list, next) {
 		if (d->domain->ops == domain->domain->ops &&
 		    d->prot == domain->prot) {
-			iommu_detach_group(domain->domain, iommu_group);
-			if (!iommu_attach_group(d->domain, iommu_group)) {
+			vfio_iommu_detach_group(domain, group);
+			if (!vfio_iommu_attach_group(d, group)) {
 				list_add(&group->next, &d->group_list);
 				iommu_domain_free(domain->domain);
 				kfree(domain);
@@ -1443,7 +1527,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 				return 0;
 			}
 
-			ret = iommu_attach_group(domain->domain, iommu_group);
+			ret = vfio_iommu_attach_group(domain, group);
 			if (ret)
 				goto out_domain;
 		}
@@ -1469,7 +1553,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 	return 0;
 
 out_detach:
-	iommu_detach_group(domain->domain, iommu_group);
+	vfio_iommu_detach_group(domain, group);
 out_domain:
 	iommu_domain_free(domain->domain);
 out_free:
@@ -1560,7 +1644,7 @@ static void vfio_iommu_type1_detach_group(void *iommu_data,
 		if (!group)
 			continue;
 
-		iommu_detach_group(domain->domain, iommu_group);
+		vfio_iommu_detach_group(domain, group);
 		list_del(&group->next);
 		kfree(group);
 		/*
@@ -1625,7 +1709,7 @@ static void vfio_release_domain(struct vfio_domain *domain, bool external)
 	list_for_each_entry_safe(group, group_tmp,
 				 &domain->group_list, next) {
 		if (!external)
-			iommu_detach_group(domain->domain, group->iommu_group);
+			vfio_iommu_detach_group(domain, group);
 		list_del(&group->next);
 		kfree(group);
 	}
-- 
2.17.1

[PATCH v3 8/8] vfio/type1: Handle different mdev isolation type

[Lu Baolu]

This adds the support to determine the isolation type
of a mediated device group by checking whether it has
an iommu device. If an iommu device exists, an iommu
domain will be allocated and then attached to the iommu
device. Otherwise, keep the same behavior as it is.

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>
Signed-off-by: Sanjay Kumar <sanjay.k.kumar@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 drivers/vfio/vfio_iommu_type1.c | 48 ++++++++++++++++++++++++++++-----
 1 file changed, 42 insertions(+), 6 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 3617499c95c9..471a95e6da66 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -1411,13 +1411,40 @@ static void vfio_iommu_detach_group(struct vfio_domain *domain,
 		iommu_detach_group(domain->domain, group->iommu_group);
 }
 
+static bool vfio_bus_is_mdev(struct bus_type *bus)
+{
+	struct bus_type *mdev_bus;
+	bool ret = false;
+
+	mdev_bus = symbol_get(mdev_bus_type);
+	if (mdev_bus) {
+		ret = (bus == mdev_bus);
+		symbol_put(mdev_bus_type);
+	}
+
+	return ret;
+}
+
+static int vfio_mdev_iommu_device(struct device *dev, void *data)
+{
+	struct device **old = data, *new;
+
+	new = vfio_mdev_get_iommu_device(dev);
+	if (*old && *old != new)
+		return -EINVAL;
+
+	*old = new;
+
+	return 0;
+}
+
 static int vfio_iommu_type1_attach_group(void *iommu_data,
 					 struct iommu_group *iommu_group)
 {
 	struct vfio_iommu *iommu = iommu_data;
 	struct vfio_group *group;
 	struct vfio_domain *domain, *d;
-	struct bus_type *bus = NULL, *mdev_bus;
+	struct bus_type *bus = NULL;
 	int ret;
 	bool resv_msi, msi_remap;
 	phys_addr_t resv_msi_base;
@@ -1452,11 +1479,18 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 	if (ret)
 		goto out_free;
 
-	mdev_bus = symbol_get(mdev_bus_type);
+	if (vfio_bus_is_mdev(bus)) {
+		struct device *iommu_device = NULL;
 
-	if (mdev_bus) {
-		if ((bus == mdev_bus) && !iommu_present(bus)) {
-			symbol_put(mdev_bus_type);
+		group->mdev_group = true;
+
+		/* Determine the isolation type */
+		ret = iommu_group_for_each_dev(iommu_group, &iommu_device,
+					       vfio_mdev_iommu_device);
+		if (ret)
+			goto out_free;
+
+		if (!iommu_device) {
 			if (!iommu->external_domain) {
 				INIT_LIST_HEAD(&domain->group_list);
 				iommu->external_domain = domain;
@@ -1466,9 +1500,11 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 			list_add(&group->next,
 				 &iommu->external_domain->group_list);
 			mutex_unlock(&iommu->lock);
+
 			return 0;
 		}
-		symbol_put(mdev_bus_type);
+
+		bus = iommu_device->bus;
 	}
 
 	domain->domain = iommu_domain_alloc(bus);
-- 
2.17.1

Re: [PATCH v3 0/8] vfio/mdev: IOMMU aware mediated device

[Xu Zaibo]

Hi,

On 2018/10/12 13:16, Lu Baolu wrote:
> Hi,
>
> The Mediate Device is a framework for fine-grained physical device
> sharing across the isolated domains. Currently the mdev framework
> is designed to be independent of the platform IOMMU support. As the
> result, the DMA isolation relies on the mdev parent device in a
> vendor specific way.
>
> There are several cases where a mediated device could be protected
> and isolated by the platform IOMMU. For example, Intel vt-d rev3.0
> [1] introduces a new translation mode called 'scalable mode', which
> enables PASID-granular translations. The vt-d scalable mode is the
> key ingredient for Scalable I/O Virtualization [2] [3] which allows
> sharing a device in minimal possible granularity (ADI - Assignable
> Device Interface).
>
> A mediated device backed by an ADI could be protected and isolated
> by the IOMMU since 1) the parent device supports tagging an unique
> PASID to all DMA traffic out of the mediated device; and 2) the DMA
> translation unit (IOMMU) supports the PASID granular translation.
> We can apply IOMMU protection and isolation to this kind of devices
> just as what we are doing with an assignable PCI device.
>
> In order to distinguish the IOMMU-capable mediated devices from those
> which still need to rely on parent devices, this patch set 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 in mdev core implementation.
>
> * 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.
>
> The mdev parent device driver could opt-in that the mdev could be
> fully isolated and protected by the IOMMU when the mdev is being
> created by invoking mdev_set_iommu_device() in its @create().
I just cannot understand here, how to get an iommu_device while I create 
mediated
device in my parent device driver?

And why not reuse the device of MDEV instread of adding a new device here?

Thanks,
Zaibo

.
>
> In the vfio_iommu_type1_attach_group(), a domain allocated through
> iommu_domain_alloc() will be attached to the mdev iommu device if
> an iommu device has been set. Otherwise, the dummy external domain
> will be used and all the DMA isolation and protection are routed to
> parent driver as the result.
>
> On IOMMU side, a basic requirement is allowing to attach multiple
> domains to a PCI device if the device advertises the capability
> and the IOMMU hardware supports finer granularity translations than
> the normal PCI Source ID based translation.
>
> As the result, a PCI device could work in two modes: normal mode
> and auxiliary mode. In the normal mode, a pci device could be
> isolated in the Source ID granularity; the pci device itself could
> be assigned to a user application by attaching a single domain
> to it. In the auxiliary mode, a pci device could be isolated in
> finer granularity, hence subsets of the device could be assigned
> to different user level application by attaching a different domain
> to each subset.
>
> The device driver is able to switch between above two modes with
> below interfaces:
>
> * iommu_get_dev_attr(dev, IOMMU_DEV_ATTR_AUXD_CAPABILITY)
>    - Represents the ability of supporting multiple domains
>      per device.
>
> * iommu_set_dev_attr(dev, IOMMU_DEV_ATTR_AUXD_ENABLE)
>    - Enable the multiple domains capability for the device
>      referenced by @dev.
>
> * iommu_set_dev_attr(dev, IOMMU_DEV_ATTR_AUXD_DISABLE)
>    - Disable the multiple domains capability for the device
>      referenced by @dev.
>
> * iommu_domain_get_attr(domain, DOMAIN_ATTR_AUXD_ID)
>    - Return ID used for finer-granularity DMA translation.
>
> The existing interfaces for attaching/detaching domains keep the
> same as before. The different behaviors between the normal mode
> and the auxiliary mode are handled in the vendor specific iommu
> drivers.
>
> In order for the ease of discussion, sometimes we call "a domain in
> auxiliary mode' or simply 'an auxiliary domain' when a domain is
> attached to a device for finer granularity translations. But we need
> to keep in mind that this doesn't mean there is a differnt domain
> type. A same domain could be bound to a device for Source ID based
> translation, and bound to another device for finer granularity
> translation at the same time.
>
> This patch series extends both IOMMU and vfio components to support
> mdev device passing through when it could be isolated and protected
> by the IOMMU units. The first part of this series (PATCH 1/08~5/08)
> adds the interfaces and implementation of the multiple domains per
> device. The second part (PATCH 6/08~8/08) adds the iommu device
> attribute to each mdev, determines isolation type according to the
> existence of an iommu device when attaching group in vfio type1 iommu
> module, and attaches the domain to iommu aware mediated devices.
>
> This patch series depends on a patch set posted here [4] for discussion
> which added scalable mode support in Intel IOMMU driver.
>
> References:
> [1] https://software.intel.com/en-us/download/intel-virtualization-technology-for-directed-io-architecture-specification
> [2] https://software.intel.com/en-us/download/intel-scalable-io-virtualization-technical-specification
> [3] https://schd.ws/hosted_files/lc32018/00/LC3-SIOV-final.pdf
> [4] https://lkml.org/lkml/2018/10/7/54
>
> Best regards,
> Lu Baolu
>
> Change log:
>    v2->v3:
>    - Remove domain type enum and use a pointer on mdev_device instead.
>    - Add a generic interface for getting/setting per device iommu
>      attributions. And use it for query aux domain capability, enable
>      aux domain and disable aux domain purpose.
>    - Reuse iommu_domain_get_attr() to retrieve the id in a aux domain.
>    - We discussed the impact of the default domain implementation
>      on reusing iommu_at(de)tach_device() interfaces. We agreed
>      that reusing iommu_at(de)tach_device() interfaces is the right
>      direction and we could tweak the code to remove the impact.
>      https://www.spinics.net/lists/kvm/msg175285.html
>    - Removed the RFC tag since no objections received.
>    - This patch has been submitted separately.
>      https://www.spinics.net/lists/kvm/msg173936.html
>
>    v1->v2:
>    - Rewrite the patches with the concept of auxiliary domains.
>
> Lu Baolu (8):
>    iommu: Add APIs for multiple domains per device
>    iommu/vt-d: Add multiple domains per device query
>    iommu/vt-d: Enable/disable multiple domains per device
>    iommu/vt-d: Attach/detach domains in auxiliary mode
>    iommu/vt-d: Return ID associated with an auxiliary domain
>    vfio/mdev: Add iommu place holders in mdev_device
>    vfio/type1: Add domain at(de)taching group helpers
>    vfio/type1: Handle different mdev isolation type
>
>   drivers/iommu/intel-iommu.c      | 249 ++++++++++++++++++++++++++++++-
>   drivers/iommu/iommu.c            |  25 ++++
>   drivers/vfio/mdev/mdev_core.c    |  36 +++++
>   drivers/vfio/mdev/mdev_private.h |   2 +
>   drivers/vfio/vfio_iommu_type1.c  | 146 ++++++++++++++++--
>   include/linux/intel-iommu.h      |  11 ++
>   include/linux/iommu.h            |  33 ++++
>   include/linux/mdev.h             |  23 +++
>   8 files changed, 509 insertions(+), 16 deletions(-)
>

Re: [PATCH v3 0/8] vfio/mdev: IOMMU aware mediated device

[Lu Baolu]

Hi,

On 10/13/2018 04:25 PM, Xu Zaibo wrote:
> Hi,
> 
> On 2018/10/12 13:16, Lu Baolu wrote:
>> Hi,
>>
>> The Mediate Device is a framework for fine-grained physical device
>> sharing across the isolated domains. Currently the mdev framework
>> is designed to be independent of the platform IOMMU support. As the
>> result, the DMA isolation relies on the mdev parent device in a
>> vendor specific way.
>>
>> There are several cases where a mediated device could be protected
>> and isolated by the platform IOMMU. For example, Intel vt-d rev3.0
>> [1] introduces a new translation mode called 'scalable mode', which
>> enables PASID-granular translations. The vt-d scalable mode is the
>> key ingredient for Scalable I/O Virtualization [2] [3] which allows
>> sharing a device in minimal possible granularity (ADI - Assignable
>> Device Interface).
>>
>> A mediated device backed by an ADI could be protected and isolated
>> by the IOMMU since 1) the parent device supports tagging an unique
>> PASID to all DMA traffic out of the mediated device; and 2) the DMA
>> translation unit (IOMMU) supports the PASID granular translation.
>> We can apply IOMMU protection and isolation to this kind of devices
>> just as what we are doing with an assignable PCI device.
>>
>> In order to distinguish the IOMMU-capable mediated devices from those
>> which still need to rely on parent devices, this patch set 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 in mdev core implementation.
>>
>> * 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.
>>
>> The mdev parent device driver could opt-in that the mdev could be
>> fully isolated and protected by the IOMMU when the mdev is being
>> created by invoking mdev_set_iommu_device() in its @create().
> I just cannot understand here, how to get an iommu_device while I create 
> mediated
> device in my parent device driver?

When you are creating an mdev in your parent driver, you should know
which PCI device this mdev belonging to.

> 
> And why not reuse the device of MDEV instread of adding a new device here?

iommu_device in the mdev_device structure represents the PCI device
that represents this mdev in iommu's device scope. IOMMU is only aware
of pci devices, it's not aware of mdev device.

Best regards,
Lu Baolu

Re: [PATCH v3 0/8] vfio/mdev: IOMMU aware mediated device

[Xu Zaibo]

Hi,

On 2018/10/15 10:48, Lu Baolu wrote:
> Hi,
>
> On 10/13/2018 04:25 PM, Xu Zaibo wrote:
>> Hi,
>>
>> On 2018/10/12 13:16, Lu Baolu wrote:
>>> Hi,
>>>
>>> The Mediate Device is a framework for fine-grained physical device
>>> sharing across the isolated domains. Currently the mdev framework
>>> is designed to be independent of the platform IOMMU support. As the
>>> result, the DMA isolation relies on the mdev parent device in a
>>> vendor specific way.
>>>
>>> There are several cases where a mediated device could be protected
>>> and isolated by the platform IOMMU. For example, Intel vt-d rev3.0
>>> [1] introduces a new translation mode called 'scalable mode', which
>>> enables PASID-granular translations. The vt-d scalable mode is the
>>> key ingredient for Scalable I/O Virtualization [2] [3] which allows
>>> sharing a device in minimal possible granularity (ADI - Assignable
>>> Device Interface).
>>>
>>> A mediated device backed by an ADI could be protected and isolated
>>> by the IOMMU since 1) the parent device supports tagging an unique
>>> PASID to all DMA traffic out of the mediated device; and 2) the DMA
>>> translation unit (IOMMU) supports the PASID granular translation.
>>> We can apply IOMMU protection and isolation to this kind of devices
>>> just as what we are doing with an assignable PCI device.
>>>
>>> In order to distinguish the IOMMU-capable mediated devices from those
>>> which still need to rely on parent devices, this patch set 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 in mdev core implementation.
>>>
>>> * 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.
>>>
>>> The mdev parent device driver could opt-in that the mdev could be
>>> fully isolated and protected by the IOMMU when the mdev is being
>>> created by invoking mdev_set_iommu_device() in its @create().
>> I just cannot understand here, how to get an iommu_device while I 
>> create mediated
>> device in my parent device driver?
>
> When you are creating an mdev in your parent driver, you should know
> which PCI device this mdev belonging to.
>

So, generally, I can set the parent device as mdev's iommu_device?
If that, however, Mdev already holds its parent device. So, I just 
figure what
differences between Mdev's parent device and iommu_device are.
>>
>> And why not reuse the device of MDEV instread of adding a new device 
>> here?
>
> iommu_device in the mdev_device structure represents the PCI device
> that represents this mdev in iommu's device scope. IOMMU is only aware
> of pci devices, it's not aware of mdev device.

Could I understand like that: IOMMU can be aware of the parent device of 
Mdev?
And more, I am doubting the necessary of iommu_device in Mdev.

Thanks,
Zaibo

.

Re: [PATCH v3 0/8] vfio/mdev: IOMMU aware mediated device

[Lu Baolu]

Hi,

On 10/15/2018 04:50 PM, Xu Zaibo wrote:
> Hi,
> 
> On 2018/10/15 10:48, Lu Baolu wrote:
>> Hi,
>>
>> On 10/13/2018 04:25 PM, Xu Zaibo wrote:
>>> Hi,
>>>
>>> On 2018/10/12 13:16, Lu Baolu wrote:
>>>> Hi,
>>>>
>>>> The Mediate Device is a framework for fine-grained physical device
>>>> sharing across the isolated domains. Currently the mdev framework
>>>> is designed to be independent of the platform IOMMU support. As the
>>>> result, the DMA isolation relies on the mdev parent device in a
>>>> vendor specific way.
>>>>
>>>> There are several cases where a mediated device could be protected
>>>> and isolated by the platform IOMMU. For example, Intel vt-d rev3.0
>>>> [1] introduces a new translation mode called 'scalable mode', which
>>>> enables PASID-granular translations. The vt-d scalable mode is the
>>>> key ingredient for Scalable I/O Virtualization [2] [3] which allows
>>>> sharing a device in minimal possible granularity (ADI - Assignable
>>>> Device Interface).
>>>>
>>>> A mediated device backed by an ADI could be protected and isolated
>>>> by the IOMMU since 1) the parent device supports tagging an unique
>>>> PASID to all DMA traffic out of the mediated device; and 2) the DMA
>>>> translation unit (IOMMU) supports the PASID granular translation.
>>>> We can apply IOMMU protection and isolation to this kind of devices
>>>> just as what we are doing with an assignable PCI device.
>>>>
>>>> In order to distinguish the IOMMU-capable mediated devices from those
>>>> which still need to rely on parent devices, this patch set 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 in mdev core implementation.
>>>>
>>>> * 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.
>>>>
>>>> The mdev parent device driver could opt-in that the mdev could be
>>>> fully isolated and protected by the IOMMU when the mdev is being
>>>> created by invoking mdev_set_iommu_device() in its @create().
>>> I just cannot understand here, how to get an iommu_device while I 
>>> create mediated
>>> device in my parent device driver?
>>
>> When you are creating an mdev in your parent driver, you should know
>> which PCI device this mdev belonging to.
>>
> 
> So, generally, I can set the parent device as mdev's iommu_device?
> If that, however, Mdev already holds its parent device. So, I just 
> figure what
> differences between Mdev's parent device and iommu_device are.
>>>
>>> And why not reuse the device of MDEV instread of adding a new device 
>>> here?
>>
>> iommu_device in the mdev_device structure represents the PCI device
>> that represents this mdev in iommu's device scope. IOMMU is only aware
>> of pci devices, it's not aware of mdev device.
> 
> Could I understand like that: IOMMU can be aware of the parent device of 
> Mdev?
> And more, I am doubting the necessary of iommu_device in Mdev.
> 

The "mdev parent device" and "mdev iommu device" are different although
they might be the same in practice. "mdev parent device" represents the
device who created the mdev. "mdev iommu device" represents the device
who shares the device context entry in iommu tables.

"mdev iommu device" is always a PCI/PCIe device since IOMMU always use
source id (bus:dev:func) to walk the device context table. But there is
no limitation on who can create an mdev, right?

Best regards,
Lu Baolu

Re: [PATCH v3 0/8] vfio/mdev: IOMMU aware mediated device

[Xu Zaibo]

Hi,

On 2018/10/16 9:21, Lu Baolu wrote:
> Hi,
>
> On 10/15/2018 04:50 PM, Xu Zaibo wrote:
>> Hi,
>>
>> On 2018/10/15 10:48, Lu Baolu wrote:
>>> Hi,
>>>
>>> On 10/13/2018 04:25 PM, Xu Zaibo wrote:
>>>> Hi,
>>>>
>>>> On 2018/10/12 13:16, Lu Baolu wrote:
>>>>> Hi,
>>>>>
>>>>> The Mediate Device is a framework for fine-grained physical device
>>>>> sharing across the isolated domains. Currently the mdev framework
>>>>> is designed to be independent of the platform IOMMU support. As the
>>>>> result, the DMA isolation relies on the mdev parent device in a
>>>>> vendor specific way.
>>>>>
>>>>> There are several cases where a mediated device could be protected
>>>>> and isolated by the platform IOMMU. For example, Intel vt-d rev3.0
>>>>> [1] introduces a new translation mode called 'scalable mode', which
>>>>> enables PASID-granular translations. The vt-d scalable mode is the
>>>>> key ingredient for Scalable I/O Virtualization [2] [3] which allows
>>>>> sharing a device in minimal possible granularity (ADI - Assignable
>>>>> Device Interface).
>>>>>
>>>>> A mediated device backed by an ADI could be protected and isolated
>>>>> by the IOMMU since 1) the parent device supports tagging an unique
>>>>> PASID to all DMA traffic out of the mediated device; and 2) the DMA
>>>>> translation unit (IOMMU) supports the PASID granular translation.
>>>>> We can apply IOMMU protection and isolation to this kind of devices
>>>>> just as what we are doing with an assignable PCI device.
>>>>>
>>>>> In order to distinguish the IOMMU-capable mediated devices from those
>>>>> which still need to rely on parent devices, this patch set 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 in mdev core implementation.
>>>>>
>>>>> * 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.
>>>>>
>>>>> The mdev parent device driver could opt-in that the mdev could be
>>>>> fully isolated and protected by the IOMMU when the mdev is being
>>>>> created by invoking mdev_set_iommu_device() in its @create().
>>>> I just cannot understand here, how to get an iommu_device while I 
>>>> create mediated
>>>> device in my parent device driver?
>>>
>>> When you are creating an mdev in your parent driver, you should know
>>> which PCI device this mdev belonging to.
>>>
>>
>> So, generally, I can set the parent device as mdev's iommu_device?
>> If that, however, Mdev already holds its parent device. So, I just 
>> figure what
>> differences between Mdev's parent device and iommu_device are.
>>>>
>>>> And why not reuse the device of MDEV instread of adding a new 
>>>> device here?
>>>
>>> iommu_device in the mdev_device structure represents the PCI device
>>> that represents this mdev in iommu's device scope. IOMMU is only aware
>>> of pci devices, it's not aware of mdev device.
>>
>> Could I understand like that: IOMMU can be aware of the parent device 
>> of Mdev?
>> And more, I am doubting the necessary of iommu_device in Mdev.
>>
>
> The "mdev parent device" and "mdev iommu device" are different although
> they might be the same in practice. "mdev parent device" represents the
> device who created the mdev. "mdev iommu device" represents the device
> who shares the device context entry in iommu tables.
>
> "mdev iommu device" is always a PCI/PCIe device since IOMMU always use
> source id (bus:dev:func) to walk the device context table. But there is
> no limitation on who can create an mdev, right?
>
Actually, I am not sure.

My understanding:
The DMA address will be issued by the parent device with PASID or 
something like that to IOMMU
facilities. However, the translation units such as iommu （PASID/page 
.etx）tables are from another
device node.  I cannot figure out how to control this in hardware level, 
or whether there will be
conflicts between the DMA transation of iommu_device and parent device.

Thanks,
Zaibo

.

Re: [PATCH v3 0/8] vfio/mdev: IOMMU aware mediated device

[Lu Baolu]

Hi,

On 10/17/18 10:02 AM, Xu Zaibo wrote:
> Hi,
> 
> On 2018/10/16 9:21, Lu Baolu wrote:
>> Hi,
>>
>> On 10/15/2018 04:50 PM, Xu Zaibo wrote:
>>> Hi,
>>>
>>> On 2018/10/15 10:48, Lu Baolu wrote:
>>>> Hi,
>>>>
>>>> On 10/13/2018 04:25 PM, Xu Zaibo wrote:
>>>>> Hi,
>>>>>
>>>>> On 2018/10/12 13:16, Lu Baolu wrote:
>>>>>> Hi,
>>>>>>
>>>>>> The Mediate Device is a framework for fine-grained physical device
>>>>>> sharing across the isolated domains. Currently the mdev framework
>>>>>> is designed to be independent of the platform IOMMU support. As the
>>>>>> result, the DMA isolation relies on the mdev parent device in a
>>>>>> vendor specific way.
>>>>>>
>>>>>> There are several cases where a mediated device could be protected
>>>>>> and isolated by the platform IOMMU. For example, Intel vt-d rev3.0
>>>>>> [1] introduces a new translation mode called 'scalable mode', which
>>>>>> enables PASID-granular translations. The vt-d scalable mode is the
>>>>>> key ingredient for Scalable I/O Virtualization [2] [3] which allows
>>>>>> sharing a device in minimal possible granularity (ADI - Assignable
>>>>>> Device Interface).
>>>>>>
>>>>>> A mediated device backed by an ADI could be protected and isolated
>>>>>> by the IOMMU since 1) the parent device supports tagging an unique
>>>>>> PASID to all DMA traffic out of the mediated device; and 2) the DMA
>>>>>> translation unit (IOMMU) supports the PASID granular translation.
>>>>>> We can apply IOMMU protection and isolation to this kind of devices
>>>>>> just as what we are doing with an assignable PCI device.
>>>>>>
>>>>>> In order to distinguish the IOMMU-capable mediated devices from those
>>>>>> which still need to rely on parent devices, this patch set 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 in mdev core implementation.
>>>>>>
>>>>>> * 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.
>>>>>>
>>>>>> The mdev parent device driver could opt-in that the mdev could be
>>>>>> fully isolated and protected by the IOMMU when the mdev is being
>>>>>> created by invoking mdev_set_iommu_device() in its @create().
>>>>> I just cannot understand here, how to get an iommu_device while I 
>>>>> create mediated
>>>>> device in my parent device driver?
>>>>
>>>> When you are creating an mdev in your parent driver, you should know
>>>> which PCI device this mdev belonging to.
>>>>
>>>
>>> So, generally, I can set the parent device as mdev's iommu_device?
>>> If that, however, Mdev already holds its parent device. So, I just 
>>> figure what
>>> differences between Mdev's parent device and iommu_device are.
>>>>>
>>>>> And why not reuse the device of MDEV instread of adding a new 
>>>>> device here?
>>>>
>>>> iommu_device in the mdev_device structure represents the PCI device
>>>> that represents this mdev in iommu's device scope. IOMMU is only aware
>>>> of pci devices, it's not aware of mdev device.
>>>
>>> Could I understand like that: IOMMU can be aware of the parent device 
>>> of Mdev?
>>> And more, I am doubting the necessary of iommu_device in Mdev.
>>>
>>
>> The "mdev parent device" and "mdev iommu device" are different although
>> they might be the same in practice. "mdev parent device" represents the
>> device who created the mdev. "mdev iommu device" represents the device
>> who shares the device context entry in iommu tables.
>>
>> "mdev iommu device" is always a PCI/PCIe device since IOMMU always use
>> source id (bus:dev:func) to walk the device context table. But there is
>> no limitation on who can create an mdev, right?
>>
> Actually, I am not sure.
> 
> My understanding:
> The DMA address will be issued by the parent device with PASID or 
> something like that to IOMMU
> facilities. However, the translation units such as iommu （PASID/page 
> .etx）tables are from another
> device node.  I cannot figure out how to control this in hardware level, 
> or whether there will be
> conflicts between the DMA transation of iommu_device and parent device.


Yes. That's the reason why these two devices are same in practice. But
conceptually, they might be different.

Best regards,
Lu Baolu