[PATCH v3 0/7] vfio/pci: SR-IOV support

[PATCH v3 0/7] vfio/pci: SR-IOV support

[Alex Williamson]

Only minor tweaks since v2, GET and SET on VFIO_DEVICE_FEATURE are
enforced mutually exclusive except with the PROBE option as suggested
by Connie, the modinfo text has been expanded for the opt-in to enable
SR-IOV support in the vfio-pci driver per discussion with Kevin.

I have not incorporated runtime warnings attempting to detect misuse
of SR-IOV or imposed a session lifetime of a VF token, both of which
were significant portions of the discussion of the v2 series.  Both of
these also seem to impose a usage model or make assumptions about VF
resource usage or configuration requirements that don't seem necessary
except for the sake of generating a warning or requiring an otherwise
unnecessary and implicit token reinitialization.  If there are new
thoughts around these or other discussion points, please raise them.

Series overview (same as provided with v1):

The synopsis of this series is that we have an ongoing desire to drive
PCIe SR-IOV PFs from userspace with VFIO.  There's an immediate need
for this with DPDK drivers and potentially interesting future use
cases in virtualization.  We've been reluctant to add this support
previously due to the dependency and trust relationship between the
VF device and PF driver.  Minimally the PF driver can induce a denial
of service to the VF, but depending on the specific implementation,
the PF driver might also be responsible for moving data between VFs
or have direct access to the state of the VF, including data or state
otherwise private to the VF or VF driver.

To help resolve these concerns, we introduce a VF token into the VFIO
PCI ABI, which acts as a shared secret key between drivers.  The
userspace PF driver is required to set the VF token to a known value
and userspace VF drivers are required to provide the token to access
the VF device.  If a PF driver is restarted with VF drivers in use, it
must also provide the current token in order to prevent a rogue
untrusted PF driver from replacing a known driver.  The degree to
which this new token is considered secret is left to the userspace
drivers, the kernel intentionally provides no means to retrieve the
current token.

Note that the above token is only required for this new model where
both the PF and VF devices are usable through vfio-pci.  Existing
models of VFIO drivers where the PF is used without SR-IOV enabled
or the VF is bound to a userspace driver with an in-kernel, host PF
driver are unaffected.

The latter configuration above also highlights a new inverted scenario
that is now possible, a userspace PF driver with in-kernel VF drivers.
I believe this is a scenario that should be allowed, but should not be
enabled by default.  This series includes code to set a default
driver_override for VFs sourced from a vfio-pci user owned PF, such
that the VFs are also bound to vfio-pci.  This model is compatible
with tools like driverctl and allows the system administrator to
decide if other bindings should be enabled.  The VF token interface
above exists only between vfio-pci PF and VF drivers, once a VF is
bound to another driver, the administrator has effectively pronounced
the device as trusted.  The vfio-pci driver will note alternate
binding in dmesg for logging and debugging purposes.

Please review, comment, and test.  The example QEMU implementation
provided with the RFC is still current for this version.  Thanks,

Alex

RFC: https://lore.kernel.org/lkml/158085337582.9445.17682266437583505502.stgit@gimli.home/
v1: https://lore.kernel.org/lkml/158145472604.16827.15751375540102298130.stgit@gimli.home/
v2: https://lore.kernel.org/lkml/158213716959.17090.8399427017403507114.stgit@gimli.home/

---

Alex Williamson (7):
      vfio: Include optional device match in vfio_device_ops callbacks
      vfio/pci: Implement match ops
      vfio/pci: Introduce VF token
      vfio: Introduce VFIO_DEVICE_FEATURE ioctl and first user
      vfio/pci: Add sriov_configure support
      vfio/pci: Remove dev_fmt definition
      vfio/pci: Cleanup .probe() exit paths


 drivers/vfio/pci/vfio_pci.c         |  390 +++++++++++++++++++++++++++++++++--
 drivers/vfio/pci/vfio_pci_private.h |   10 +
 drivers/vfio/vfio.c                 |   20 +-
 include/linux/vfio.h                |    4 
 include/uapi/linux/vfio.h           |   37 +++
 5 files changed, 433 insertions(+), 28 deletions(-)

[PATCH v3 1/7] vfio: Include optional device match in vfio_device_ops callbacks

[Alex Williamson]

Allow bus drivers to provide their own callback to match a device to
the user provided string.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/vfio.c  |   20 ++++++++++++++++----
 include/linux/vfio.h |    4 ++++
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index c8482624ca34..0bd77d6ea691 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -875,11 +875,23 @@ EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);
 static struct vfio_device *vfio_device_get_from_name(struct vfio_group *group,
 						     char *buf)
 {
-	struct vfio_device *it, *device = NULL;
+	struct vfio_device *it, *device = ERR_PTR(-ENODEV);
 
 	mutex_lock(&group->device_lock);
 	list_for_each_entry(it, &group->device_list, group_next) {
-		if (!strcmp(dev_name(it->dev), buf)) {
+		int ret;
+
+		if (it->ops->match) {
+			ret = it->ops->match(it->device_data, buf);
+			if (ret < 0) {
+				device = ERR_PTR(ret);
+				break;
+			}
+		} else {
+			ret = !strcmp(dev_name(it->dev), buf);
+		}
+
+		if (ret) {
 			device = it;
 			vfio_device_get(device);
 			break;
@@ -1430,8 +1442,8 @@ static int vfio_group_get_device_fd(struct vfio_group *group, char *buf)
 		return -EPERM;
 
 	device = vfio_device_get_from_name(group, buf);
-	if (!device)
-		return -ENODEV;
+	if (IS_ERR(device))
+		return PTR_ERR(device);
 
 	ret = device->ops->open(device->device_data);
 	if (ret) {
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index e42a711a2800..029694b977f2 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -26,6 +26,9 @@
  *         operations documented below
  * @mmap: Perform mmap(2) on a region of the device file descriptor
  * @request: Request for the bus driver to release the device
+ * @match: Optional device name match callback (return: 0 for no-match, >0 for
+ *         match, -errno for abort (ex. match with insufficient or incorrect
+ *         additional args)
  */
 struct vfio_device_ops {
 	char	*name;
@@ -39,6 +42,7 @@ struct vfio_device_ops {
 			 unsigned long arg);
 	int	(*mmap)(void *device_data, struct vm_area_struct *vma);
 	void	(*request)(void *device_data, unsigned int count);
+	int	(*match)(void *device_data, char *buf);
 };
 
 extern struct iommu_group *vfio_iommu_group_get(struct device *dev);

[PATCH v3 2/7] vfio/pci: Implement match ops

[Alex Williamson]

This currently serves the same purpose as the default implementation
but will be expanded for additional functionality.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/pci/vfio_pci.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 379a02c36e37..2ec6c31d0ab0 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -1278,6 +1278,13 @@ static void vfio_pci_request(void *device_data, unsigned int count)
 	mutex_unlock(&vdev->igate);
 }
 
+static int vfio_pci_match(void *device_data, char *buf)
+{
+	struct vfio_pci_device *vdev = device_data;
+
+	return !strcmp(pci_name(vdev->pdev), buf);
+}
+
 static const struct vfio_device_ops vfio_pci_ops = {
 	.name		= "vfio-pci",
 	.open		= vfio_pci_open,
@@ -1287,6 +1294,7 @@ static const struct vfio_device_ops vfio_pci_ops = {
 	.write		= vfio_pci_write,
 	.mmap		= vfio_pci_mmap,
 	.request	= vfio_pci_request,
+	.match		= vfio_pci_match,
 };
 
 static int vfio_pci_reflck_attach(struct vfio_pci_device *vdev);

[PATCH v3 3/7] vfio/pci: Introduce VF token

[Alex Williamson]

If we enable SR-IOV on a vfio-pci owned PF, the resulting VFs are not
fully isolated from the PF.  The PF can always cause a denial of service
to the VF, even if by simply resetting itself.  The degree to which a PF
can access the data passed through a VF or interfere with its operation
is dependent on a given SR-IOV implementation.  Therefore we want to
avoid a scenario where an existing vfio-pci based userspace driver might
assume the PF driver is trusted, for example assigning a PF to one VM
and VF to another with some expectation of isolation.  IOMMU grouping
could be a solution to this, but imposes an unnecessarily strong
relationship between PF and VF drivers if they need to operate with the
same IOMMU context.  Instead we introduce a "VF token", which is
essentially just a shared secret between PF and VF drivers, implemented
as a UUID.

The VF token can be set by a vfio-pci based PF driver and must be known
by the vfio-pci based VF driver in order to gain access to the device.
This allows the degree to which this VF token is considered secret to be
determined by the applications and environment.  For example a VM might
generate a random UUID known only internally to the hypervisor while a
userspace networking appliance might use a shared, or even well know,
UUID among the application drivers.

To incorporate this VF token, the VFIO_GROUP_GET_DEVICE_FD interface is
extended to accept key=value pairs in addition to the device name.  This
allows us to most easily deny user access to the device without risk
that existing userspace drivers assume region offsets, IRQs, and other
device features, leading to more elaborate error paths.  The format of
these options are expected to take the form:

"$DEVICE_NAME $OPTION1=$VALUE1 $OPTION2=$VALUE2"

Where the device name is always provided first for compatibility and
additional options are specified in a space separated list.  The
relation between and requirements for the additional options will be
vfio bus driver dependent, however unknown or unused option within this
schema should return error.  This allow for future use of unknown
options as well as a positive indication to the user that an option is
used.

An example VF token option would take this form:

"0000:03:00.0 vf_token=2ab74924-c335-45f4-9b16-8569e5b08258"

When accessing a VF where the PF is making use of vfio-pci, the user
MUST provide the current vf_token.  When accessing a PF, the user MUST
provide the current vf_token IF there are active VF users or MAY provide
a vf_token in order to set the current VF token when no VF users are
active.  The former requirement assures VF users that an unassociated
driver cannot usurp the PF device.  These semantics also imply that a
VF token MUST be set by a PF driver before VF drivers can access their
device, the default token is random and mechanisms to read the token are
not provided in order to protect the VF token of previous users.  Use of
the vf_token option outside of these cases will return an error, as
discussed above.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/pci/vfio_pci.c         |  198 +++++++++++++++++++++++++++++++++++
 drivers/vfio/pci/vfio_pci_private.h |    8 +
 2 files changed, 205 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 2ec6c31d0ab0..5277c6c2fa72 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -466,6 +466,44 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
 		vfio_pci_set_power_state(vdev, PCI_D3hot);
 }
 
+static struct pci_driver vfio_pci_driver;
+
+static struct vfio_pci_device *get_pf_vdev(struct vfio_pci_device *vdev,
+					   struct vfio_device **pf_dev)
+{
+	struct pci_dev *physfn = pci_physfn(vdev->pdev);
+
+	if (!vdev->pdev->is_virtfn)
+		return NULL;
+
+	*pf_dev = vfio_device_get_from_dev(&physfn->dev);
+	if (!*pf_dev)
+		return NULL;
+
+	if (pci_dev_driver(physfn) != &vfio_pci_driver) {
+		vfio_device_put(*pf_dev);
+		return NULL;
+	}
+
+	return vfio_device_data(*pf_dev);
+}
+
+static void vfio_pci_vf_token_user_add(struct vfio_pci_device *vdev, int val)
+{
+	struct vfio_device *pf_dev;
+	struct vfio_pci_device *pf_vdev = get_pf_vdev(vdev, &pf_dev);
+
+	if (!pf_vdev)
+		return;
+
+	mutex_lock(&pf_vdev->vf_token->lock);
+	pf_vdev->vf_token->users += val;
+	WARN_ON(pf_vdev->vf_token->users < 0);
+	mutex_unlock(&pf_vdev->vf_token->lock);
+
+	vfio_device_put(pf_dev);
+}
+
 static void vfio_pci_release(void *device_data)
 {
 	struct vfio_pci_device *vdev = device_data;
@@ -473,6 +511,7 @@ static void vfio_pci_release(void *device_data)
 	mutex_lock(&vdev->reflck->lock);
 
 	if (!(--vdev->refcnt)) {
+		vfio_pci_vf_token_user_add(vdev, -1);
 		vfio_spapr_pci_eeh_release(vdev->pdev);
 		vfio_pci_disable(vdev);
 	}
@@ -498,6 +537,7 @@ static int vfio_pci_open(void *device_data)
 			goto error;
 
 		vfio_spapr_pci_eeh_open(vdev->pdev);
+		vfio_pci_vf_token_user_add(vdev, 1);
 	}
 	vdev->refcnt++;
 error:
@@ -1278,11 +1318,148 @@ static void vfio_pci_request(void *device_data, unsigned int count)
 	mutex_unlock(&vdev->igate);
 }
 
+static int vfio_pci_validate_vf_token(struct vfio_pci_device *vdev,
+				      bool vf_token, uuid_t *uuid)
+{
+	/*
+	 * There's always some degree of trust or collaboration between SR-IOV
+	 * PF and VFs, even if just that the PF hosts the SR-IOV capability and
+	 * can disrupt VFs with a reset, but often the PF has more explicit
+	 * access to deny service to the VF or access data passed through the
+	 * VF.  We therefore require an opt-in via a shared VF token (UUID) to
+	 * represent this trust.  This both prevents that a VF driver might
+	 * assume the PF driver is a trusted, in-kernel driver, and also that
+	 * a PF driver might be replaced with a rogue driver, unknown to in-use
+	 * VF drivers.
+	 *
+	 * Therefore when presented with a VF, if the PF is a vfio device and
+	 * it is bound to the vfio-pci driver, the user needs to provide a VF
+	 * token to access the device, in the form of appending a vf_token to
+	 * the device name, for example:
+	 *
+	 * "0000:04:10.0 vf_token=bd8d9d2b-5a5f-4f5a-a211-f591514ba1f3"
+	 *
+	 * When presented with a PF which has VFs in use, the user must also
+	 * provide the current VF token to prove collaboration with existing
+	 * VF users.  If VFs are not in use, the VF token provided for the PF
+	 * device will act to set the VF token.
+	 *
+	 * If the VF token is provided but unused, an error is generated.
+	 */
+	if (!vdev->pdev->is_virtfn && !vdev->vf_token && !vf_token)
+		return 0; /* No VF token provided or required */
+
+	if (vdev->pdev->is_virtfn) {
+		struct vfio_device *pf_dev;
+		struct vfio_pci_device *pf_vdev = get_pf_vdev(vdev, &pf_dev);
+		bool match;
+
+		if (!pf_vdev) {
+			if (!vf_token)
+				return 0; /* PF is not vfio-pci, no VF token */
+
+			pci_info_ratelimited(vdev->pdev,
+				"VF token incorrectly provided, PF not bound to vfio-pci\n");
+			return -EINVAL;
+		}
+
+		if (!vf_token) {
+			vfio_device_put(pf_dev);
+			pci_info_ratelimited(vdev->pdev,
+				"VF token required to access device\n");
+			return -EACCES;
+		}
+
+		mutex_lock(&pf_vdev->vf_token->lock);
+		match = uuid_equal(uuid, &pf_vdev->vf_token->uuid);
+		mutex_unlock(&pf_vdev->vf_token->lock);
+
+		vfio_device_put(pf_dev);
+
+		if (!match) {
+			pci_info_ratelimited(vdev->pdev,
+				"Incorrect VF token provided for device\n");
+			return -EACCES;
+		}
+	} else if (vdev->vf_token) {
+		mutex_lock(&vdev->vf_token->lock);
+		if (vdev->vf_token->users) {
+			if (!vf_token) {
+				mutex_unlock(&vdev->vf_token->lock);
+				pci_info_ratelimited(vdev->pdev,
+					"VF token required to access device\n");
+				return -EACCES;
+			}
+
+			if (!uuid_equal(uuid, &vdev->vf_token->uuid)) {
+				mutex_unlock(&vdev->vf_token->lock);
+				pci_info_ratelimited(vdev->pdev,
+					"Incorrect VF token provided for device\n");
+				return -EACCES;
+			}
+		} else if (vf_token) {
+			uuid_copy(&vdev->vf_token->uuid, uuid);
+		}
+
+		mutex_unlock(&vdev->vf_token->lock);
+	} else if (vf_token) {
+		pci_info_ratelimited(vdev->pdev,
+			"VF token incorrectly provided, not a PF or VF\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+#define VF_TOKEN_ARG "vf_token="
+
 static int vfio_pci_match(void *device_data, char *buf)
 {
 	struct vfio_pci_device *vdev = device_data;
+	bool vf_token = false;
+	uuid_t uuid;
+	int ret;
+
+	if (strncmp(pci_name(vdev->pdev), buf, strlen(pci_name(vdev->pdev))))
+		return 0; /* No match */
+
+	if (strlen(buf) > strlen(pci_name(vdev->pdev))) {
+		buf += strlen(pci_name(vdev->pdev));
+
+		if (*buf != ' ')
+			return 0; /* No match: non-whitespace after name */
+
+		while (*buf) {
+			if (*buf == ' ') {
+				buf++;
+				continue;
+			}
+
+			if (!vf_token && !strncmp(buf, VF_TOKEN_ARG,
+						  strlen(VF_TOKEN_ARG))) {
+				buf += strlen(VF_TOKEN_ARG);
+
+				if (strlen(buf) < UUID_STRING_LEN)
+					return -EINVAL;
+
+				ret = uuid_parse(buf, &uuid);
+				if (ret)
+					return ret;
 
-	return !strcmp(pci_name(vdev->pdev), buf);
+				vf_token = true;
+				buf += UUID_STRING_LEN;
+			} else {
+				/* Unknown/duplicate option */
+				return -EINVAL;
+			}
+		}
+	}
+
+	ret = vfio_pci_validate_vf_token(vdev, vf_token, &uuid);
+	if (ret)
+		return ret;
+
+	return 1; /* Match */
 }
 
 static const struct vfio_device_ops vfio_pci_ops = {
@@ -1354,6 +1531,19 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 		return ret;
 	}
 
+	if (pdev->is_physfn) {
+		vdev->vf_token = kzalloc(sizeof(*vdev->vf_token), GFP_KERNEL);
+		if (!vdev->vf_token) {
+			vfio_pci_reflck_put(vdev->reflck);
+			vfio_del_group_dev(&pdev->dev);
+			vfio_iommu_group_put(group, &pdev->dev);
+			kfree(vdev);
+			return -ENOMEM;
+		}
+		mutex_init(&vdev->vf_token->lock);
+		uuid_gen(&vdev->vf_token->uuid);
+	}
+
 	if (vfio_pci_is_vga(pdev)) {
 		vga_client_register(pdev, vdev, NULL, vfio_pci_set_vga_decode);
 		vga_set_legacy_decoding(pdev,
@@ -1387,6 +1577,12 @@ static void vfio_pci_remove(struct pci_dev *pdev)
 	if (!vdev)
 		return;
 
+	if (vdev->vf_token) {
+		WARN_ON(vdev->vf_token->users);
+		mutex_destroy(&vdev->vf_token->lock);
+		kfree(vdev->vf_token);
+	}
+
 	vfio_pci_reflck_put(vdev->reflck);
 
 	vfio_iommu_group_put(pdev->dev.iommu_group, &pdev->dev);
diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
index 8a2c7607d513..76c11c915949 100644
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -12,6 +12,7 @@
 #include <linux/pci.h>
 #include <linux/irqbypass.h>
 #include <linux/types.h>
+#include <linux/uuid.h>
 
 #ifndef VFIO_PCI_PRIVATE_H
 #define VFIO_PCI_PRIVATE_H
@@ -84,6 +85,12 @@ struct vfio_pci_reflck {
 	struct mutex		lock;
 };
 
+struct vfio_pci_vf_token {
+	struct mutex		lock;
+	uuid_t			uuid;
+	int			users;
+};
+
 struct vfio_pci_device {
 	struct pci_dev		*pdev;
 	void __iomem		*barmap[PCI_STD_NUM_BARS];
@@ -122,6 +129,7 @@ struct vfio_pci_device {
 	struct list_head	dummy_resources_list;
 	struct mutex		ioeventfds_lock;
 	struct list_head	ioeventfds_list;
+	struct vfio_pci_vf_token	*vf_token;
 };
 
 #define is_intx(vdev) (vdev->irq_type == VFIO_PCI_INTX_IRQ_INDEX)

Re: [PATCH v3 3/7] vfio/pci: Introduce VF token

[Cornelia Huck]

On Wed, 11 Mar 2020 15:58:52 -0600
Alex Williamson <alex.williamson@redhat.com> wrote:

> If we enable SR-IOV on a vfio-pci owned PF, the resulting VFs are not
> fully isolated from the PF.  The PF can always cause a denial of service
> to the VF, even if by simply resetting itself.  The degree to which a PF
> can access the data passed through a VF or interfere with its operation
> is dependent on a given SR-IOV implementation.  Therefore we want to
> avoid a scenario where an existing vfio-pci based userspace driver might
> assume the PF driver is trusted, for example assigning a PF to one VM
> and VF to another with some expectation of isolation.  IOMMU grouping
> could be a solution to this, but imposes an unnecessarily strong
> relationship between PF and VF drivers if they need to operate with the
> same IOMMU context.  Instead we introduce a "VF token", which is
> essentially just a shared secret between PF and VF drivers, implemented
> as a UUID.
> 
> The VF token can be set by a vfio-pci based PF driver and must be known
> by the vfio-pci based VF driver in order to gain access to the device.
> This allows the degree to which this VF token is considered secret to be
> determined by the applications and environment.  For example a VM might
> generate a random UUID known only internally to the hypervisor while a
> userspace networking appliance might use a shared, or even well know,
> UUID among the application drivers.
> 
> To incorporate this VF token, the VFIO_GROUP_GET_DEVICE_FD interface is
> extended to accept key=value pairs in addition to the device name.  This
> allows us to most easily deny user access to the device without risk
> that existing userspace drivers assume region offsets, IRQs, and other
> device features, leading to more elaborate error paths.  The format of
> these options are expected to take the form:
> 
> "$DEVICE_NAME $OPTION1=$VALUE1 $OPTION2=$VALUE2"
> 
> Where the device name is always provided first for compatibility and
> additional options are specified in a space separated list.  The
> relation between and requirements for the additional options will be
> vfio bus driver dependent, however unknown or unused option within this
> schema should return error.  This allow for future use of unknown
> options as well as a positive indication to the user that an option is
> used.
> 
> An example VF token option would take this form:
> 
> "0000:03:00.0 vf_token=2ab74924-c335-45f4-9b16-8569e5b08258"
> 
> When accessing a VF where the PF is making use of vfio-pci, the user
> MUST provide the current vf_token.  When accessing a PF, the user MUST
> provide the current vf_token IF there are active VF users or MAY provide
> a vf_token in order to set the current VF token when no VF users are
> active.  The former requirement assures VF users that an unassociated
> driver cannot usurp the PF device.  These semantics also imply that a
> VF token MUST be set by a PF driver before VF drivers can access their
> device, the default token is random and mechanisms to read the token are
> not provided in order to protect the VF token of previous users.  Use of
> the vf_token option outside of these cases will return an error, as
> discussed above.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  drivers/vfio/pci/vfio_pci.c         |  198 +++++++++++++++++++++++++++++++++++
>  drivers/vfio/pci/vfio_pci_private.h |    8 +
>  2 files changed, 205 insertions(+), 1 deletion(-)

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

[PATCH v3 4/7] vfio: Introduce VFIO_DEVICE_FEATURE ioctl and first user

[Alex Williamson]

The VFIO_DEVICE_FEATURE ioctl is meant to be a general purpose, device
agnostic ioctl for setting, retrieving, and probing device features.
This implementation provides a 16-bit field for specifying a feature
index, where the data porition of the ioctl is determined by the
semantics for the given feature.  Additional flag bits indicate the
direction and nature of the operation; SET indicates user data is
provided into the device feature, GET indicates the device feature is
written out into user data.  The PROBE flag augments determining
whether the given feature is supported, and if provided, whether the
given operation on the feature is supported.

The first user of this ioctl is for setting the vfio-pci VF token,
where the user provides a shared secret key (UUID) on a SR-IOV PF
device, which users must provide when opening associated VF devices.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/pci/vfio_pci.c |   59 +++++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/vfio.h   |   37 +++++++++++++++++++++++++++
 2 files changed, 96 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 5277c6c2fa72..6c28860f768a 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -1180,6 +1180,65 @@ static long vfio_pci_ioctl(void *device_data,
 
 		return vfio_pci_ioeventfd(vdev, ioeventfd.offset,
 					  ioeventfd.data, count, ioeventfd.fd);
+	} else if (cmd == VFIO_DEVICE_FEATURE) {
+		struct vfio_device_feature feature;
+		uuid_t uuid;
+
+		minsz = offsetofend(struct vfio_device_feature, flags);
+
+		if (copy_from_user(&feature, (void __user *)arg, minsz))
+			return -EFAULT;
+
+		if (feature.argsz < minsz)
+			return -EINVAL;
+
+		/* Check unknown flags */
+		if (feature.flags & ~(VFIO_DEVICE_FEATURE_MASK |
+				      VFIO_DEVICE_FEATURE_SET |
+				      VFIO_DEVICE_FEATURE_GET |
+				      VFIO_DEVICE_FEATURE_PROBE))
+			return -EINVAL;
+
+		/* GET & SET are mutually exclusive except with PROBE */
+		if (!(feature.flags & VFIO_DEVICE_FEATURE_PROBE) &&
+		    (feature.flags & VFIO_DEVICE_FEATURE_SET) &&
+		    (feature.flags & VFIO_DEVICE_FEATURE_GET))
+			return -EINVAL;
+
+		switch (feature.flags & VFIO_DEVICE_FEATURE_MASK) {
+		case VFIO_DEVICE_FEATURE_PCI_VF_TOKEN:
+			if (!vdev->vf_token)
+				return -ENOTTY;
+
+			/*
+			 * We do not support GET of the VF Token UUID as this
+			 * could expose the token of the previous device user.
+			 */
+			if (feature.flags & VFIO_DEVICE_FEATURE_GET)
+				return -EINVAL;
+
+			if (feature.flags & VFIO_DEVICE_FEATURE_PROBE)
+				return 0;
+
+			/* Don't SET unless told to do so */
+			if (!(feature.flags & VFIO_DEVICE_FEATURE_SET))
+				return -EINVAL;
+
+			if (feature.argsz < minsz + sizeof(uuid))
+				return -EINVAL;
+
+			if (copy_from_user(&uuid, (void __user *)(arg + minsz),
+					   sizeof(uuid)))
+				return -EFAULT;
+
+			mutex_lock(&vdev->vf_token->lock);
+			uuid_copy(&vdev->vf_token->uuid, &uuid);
+			mutex_unlock(&vdev->vf_token->lock);
+
+			return 0;
+		default:
+			return -ENOTTY;
+		}
 	}
 
 	return -ENOTTY;
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 9e843a147ead..aa37f90a2180 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -707,6 +707,43 @@ struct vfio_device_ioeventfd {
 
 #define VFIO_DEVICE_IOEVENTFD		_IO(VFIO_TYPE, VFIO_BASE + 16)
 
+/**
+ * VFIO_DEVICE_FEATURE - _IORW(VFIO_TYPE, VFIO_BASE + 17,
+ *			       struct vfio_device_feature)
+ *
+ * Get, set, or probe feature data of the device.  The feature is selected
+ * using the FEATURE_MASK portion of the flags field.  Support for a feature
+ * can be probed by setting both the FEATURE_MASK and PROBE bits.  A probe
+ * may optionally include the GET and/or SET bits to determine read vs write
+ * access of the feature respectively.  Probing a feature will return success
+ * if the feature is supported and all of the optionally indicated GET/SET
+ * methods are supported.  The format of the data portion of the structure is
+ * specific to the given feature.  The data portion is not required for
+ * probing.
+ *
+ * Return 0 on success, -errno on failure.
+ */
+struct vfio_device_feature {
+	__u32	argsz;
+	__u32	flags;
+#define VFIO_DEVICE_FEATURE_MASK	(0xffff) /* 16-bit feature index */
+#define VFIO_DEVICE_FEATURE_GET		(1 << 16) /* Get feature into data[] */
+#define VFIO_DEVICE_FEATURE_SET		(1 << 17) /* Set feature from data[] */
+#define VFIO_DEVICE_FEATURE_PROBE	(1 << 18) /* Probe feature support */
+	__u8	data[];
+};
+
+#define VFIO_DEVICE_FEATURE		_IO(VFIO_TYPE, VFIO_BASE + 17)
+
+/*
+ * Provide support for setting a PCI VF Token, which is used as a shared
+ * secret between PF and VF drivers.  This feature may only be set on a
+ * PCI SR-IOV PF when SR-IOV is enabled on the PF and there are no existing
+ * open VFs.  Data provided when setting this feature is a 16-byte array
+ * (__u8 b[16]), representing a UUID.
+ */
+#define VFIO_DEVICE_FEATURE_PCI_VF_TOKEN	(0)
+
 /* -------- API for Type1 VFIO IOMMU -------- */
 
 /**

Re: [PATCH v3 4/7] vfio: Introduce VFIO_DEVICE_FEATURE ioctl and first user

[Cornelia Huck]

On Wed, 11 Mar 2020 15:59:01 -0600
Alex Williamson <alex.williamson@redhat.com> wrote:

> The VFIO_DEVICE_FEATURE ioctl is meant to be a general purpose, device
> agnostic ioctl for setting, retrieving, and probing device features.
> This implementation provides a 16-bit field for specifying a feature
> index, where the data porition of the ioctl is determined by the
> semantics for the given feature.  Additional flag bits indicate the
> direction and nature of the operation; SET indicates user data is
> provided into the device feature, GET indicates the device feature is
> written out into user data.  The PROBE flag augments determining
> whether the given feature is supported, and if provided, whether the
> given operation on the feature is supported.
> 
> The first user of this ioctl is for setting the vfio-pci VF token,
> where the user provides a shared secret key (UUID) on a SR-IOV PF
> device, which users must provide when opening associated VF devices.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  drivers/vfio/pci/vfio_pci.c |   59 +++++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/vfio.h   |   37 +++++++++++++++++++++++++++
>  2 files changed, 96 insertions(+)

(...)

> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 9e843a147ead..aa37f90a2180 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -707,6 +707,43 @@ struct vfio_device_ioeventfd {
>  
>  #define VFIO_DEVICE_IOEVENTFD		_IO(VFIO_TYPE, VFIO_BASE + 16)
>  
> +/**
> + * VFIO_DEVICE_FEATURE - _IORW(VFIO_TYPE, VFIO_BASE + 17,
> + *			       struct vfio_device_feature)
> + *
> + * Get, set, or probe feature data of the device.  The feature is selected
> + * using the FEATURE_MASK portion of the flags field.  Support for a feature
> + * can be probed by setting both the FEATURE_MASK and PROBE bits.  A probe
> + * may optionally include the GET and/or SET bits to determine read vs write
> + * access of the feature respectively.  Probing a feature will return success
> + * if the feature is supported and all of the optionally indicated GET/SET
> + * methods are supported.  The format of the data portion of the structure is
> + * specific to the given feature.  The data portion is not required for
> + * probing.

Maybe add

"GET and SET are mutually exclusive, unless PROBE is also specified."

?

> + *
> + * Return 0 on success, -errno on failure.
> + */
> +struct vfio_device_feature {
> +	__u32	argsz;
> +	__u32	flags;
> +#define VFIO_DEVICE_FEATURE_MASK	(0xffff) /* 16-bit feature index */
> +#define VFIO_DEVICE_FEATURE_GET		(1 << 16) /* Get feature into data[] */
> +#define VFIO_DEVICE_FEATURE_SET		(1 << 17) /* Set feature from data[] */
> +#define VFIO_DEVICE_FEATURE_PROBE	(1 << 18) /* Probe feature support */
> +	__u8	data[];
> +};
> +
> +#define VFIO_DEVICE_FEATURE		_IO(VFIO_TYPE, VFIO_BASE + 17)
> +
> +/*
> + * Provide support for setting a PCI VF Token, which is used as a shared
> + * secret between PF and VF drivers.  This feature may only be set on a
> + * PCI SR-IOV PF when SR-IOV is enabled on the PF and there are no existing
> + * open VFs.  Data provided when setting this feature is a 16-byte array
> + * (__u8 b[16]), representing a UUID.
> + */
> +#define VFIO_DEVICE_FEATURE_PCI_VF_TOKEN	(0)
> +
>  /* -------- API for Type1 VFIO IOMMU -------- */
>  
>  /**
> 

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

[PATCH v3 5/7] vfio/pci: Add sriov_configure support

[Alex Williamson]

With the VF Token interface we can now expect that a vfio userspace
driver must be in collaboration with the PF driver, an unwitting
userspace driver will not be able to get past the GET_DEVICE_FD step
in accessing the device.  We can now move on to actually allowing
SR-IOV to be enabled by vfio-pci on the PF.  Support for this is not
enabled by default in this commit, but it does provide a module option
for this to be enabled (enable_sriov=1).  Enabling VFs is rather
straightforward, except we don't want to risk that a VF might get
autoprobed and bound to other drivers, so a bus notifier is used to
"capture" VFs to vfio-pci using the driver_override support.  We
assume any later action to bind the device to other drivers is
condoned by the system admin and allow it with a log warning.

vfio-pci will disable SR-IOV on a PF before releasing the device,
allowing a VF driver to be assured other drivers cannot take over the
PF and that any other userspace driver must know the shared VF token.
This support also does not provide a mechanism for the PF userspace
driver itself to manipulate SR-IOV through the vfio API.  With this
patch SR-IOV can only be enabled via the host sysfs interface and the
PF driver user cannot create or remove VFs.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/pci/vfio_pci.c         |  106 +++++++++++++++++++++++++++++++----
 drivers/vfio/pci/vfio_pci_private.h |    2 +
 2 files changed, 97 insertions(+), 11 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 6c28860f768a..df6bae75c8dd 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -54,6 +54,12 @@ module_param(disable_idle_d3, bool, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(disable_idle_d3,
 		 "Disable using the PCI D3 low power state for idle, unused devices");
 
+static bool enable_sriov;
+#ifdef CONFIG_PCI_IOV
+module_param(enable_sriov, bool, 0644);
+MODULE_PARM_DESC(enable_sriov, "Enable support for SR-IOV configuration.  Enabling SR-IOV on a PF typically requires support of the userspace PF driver, enabling VFs without such support may result in non-functional VFs or PF.");
+#endif
+
 static inline bool vfio_vga_disabled(void)
 {
 #ifdef CONFIG_VFIO_PCI_VGA
@@ -1535,6 +1541,35 @@ static const struct vfio_device_ops vfio_pci_ops = {
 
 static int vfio_pci_reflck_attach(struct vfio_pci_device *vdev);
 static void vfio_pci_reflck_put(struct vfio_pci_reflck *reflck);
+static struct pci_driver vfio_pci_driver;
+
+static int vfio_pci_bus_notifier(struct notifier_block *nb,
+				 unsigned long action, void *data)
+{
+	struct vfio_pci_device *vdev = container_of(nb,
+						    struct vfio_pci_device, nb);
+	struct device *dev = data;
+	struct pci_dev *pdev = to_pci_dev(dev);
+	struct pci_dev *physfn = pci_physfn(pdev);
+
+	if (action == BUS_NOTIFY_ADD_DEVICE &&
+	    pdev->is_virtfn && physfn == vdev->pdev) {
+		pci_info(vdev->pdev, "Captured SR-IOV VF %s driver_override\n",
+			 pci_name(pdev));
+		pdev->driver_override = kasprintf(GFP_KERNEL, "%s",
+						  vfio_pci_ops.name);
+	} else if (action == BUS_NOTIFY_BOUND_DRIVER &&
+		   pdev->is_virtfn && physfn == vdev->pdev) {
+		struct pci_driver *drv = pci_dev_driver(pdev);
+
+		if (drv && drv != &vfio_pci_driver)
+			pci_warn(vdev->pdev,
+				 "VF %s bound to driver %s while PF bound to vfio-pci\n",
+				 pci_name(pdev), drv->name);
+	}
+
+	return 0;
+}
 
 static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 {
@@ -1546,12 +1581,12 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 		return -EINVAL;
 
 	/*
-	 * Prevent binding to PFs with VFs enabled, this too easily allows
-	 * userspace instance with VFs and PFs from the same device, which
-	 * cannot work.  Disabling SR-IOV here would initiate removing the
-	 * VFs, which would unbind the driver, which is prone to blocking
-	 * if that VF is also in use by vfio-pci.  Just reject these PFs
-	 * and let the user sort it out.
+	 * Prevent binding to PFs with VFs enabled, the VFs might be in use
+	 * by the host or other users.  We cannot capture the VFs if they
+	 * already exist, nor can we track VF users.  Disabling SR-IOV here
+	 * would initiate removing the VFs, which would unbind the driver,
+	 * which is prone to blocking if that VF is also in use by vfio-pci.
+	 * Just reject these PFs and let the user sort it out.
 	 */
 	if (pci_num_vf(pdev)) {
 		pci_warn(pdev, "Cannot bind to PF with SR-IOV enabled\n");
@@ -1599,6 +1634,18 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 			kfree(vdev);
 			return -ENOMEM;
 		}
+
+		vdev->nb.notifier_call = vfio_pci_bus_notifier;
+		ret = bus_register_notifier(&pci_bus_type, &vdev->nb);
+		if (ret) {
+			kfree(vdev->vf_token);
+			vfio_pci_reflck_put(vdev->reflck);
+			vfio_del_group_dev(&pdev->dev);
+			vfio_iommu_group_put(group, &pdev->dev);
+			kfree(vdev);
+			return ret;
+		}
+
 		mutex_init(&vdev->vf_token->lock);
 		uuid_gen(&vdev->vf_token->uuid);
 	}
@@ -1632,6 +1679,8 @@ static void vfio_pci_remove(struct pci_dev *pdev)
 {
 	struct vfio_pci_device *vdev;
 
+	pci_disable_sriov(pdev);
+
 	vdev = vfio_del_group_dev(&pdev->dev);
 	if (!vdev)
 		return;
@@ -1642,6 +1691,9 @@ static void vfio_pci_remove(struct pci_dev *pdev)
 		kfree(vdev->vf_token);
 	}
 
+	if (vdev->nb.notifier_call)
+		bus_unregister_notifier(&pci_bus_type, &vdev->nb);
+
 	vfio_pci_reflck_put(vdev->reflck);
 
 	vfio_iommu_group_put(pdev->dev.iommu_group, &pdev->dev);
@@ -1690,16 +1742,48 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
 	return PCI_ERS_RESULT_CAN_RECOVER;
 }
 
+static int vfio_pci_sriov_configure(struct pci_dev *pdev, int nr_virtfn)
+{
+	struct vfio_pci_device *vdev;
+	struct vfio_device *device;
+	int ret = 0;
+
+	might_sleep();
+
+	if (!enable_sriov)
+		return -ENOENT;
+
+	device = vfio_device_get_from_dev(&pdev->dev);
+	if (!device)
+		return -ENODEV;
+
+	vdev = vfio_device_data(device);
+	if (!vdev) {
+		vfio_device_put(device);
+		return -ENODEV;
+	}
+
+	if (nr_virtfn == 0)
+		pci_disable_sriov(pdev);
+	else
+		ret = pci_enable_sriov(pdev, nr_virtfn);
+
+	vfio_device_put(device);
+
+	return ret < 0 ? ret : nr_virtfn;
+}
+
 static const struct pci_error_handlers vfio_err_handlers = {
 	.error_detected = vfio_pci_aer_err_detected,
 };
 
 static struct pci_driver vfio_pci_driver = {
-	.name		= "vfio-pci",
-	.id_table	= NULL, /* only dynamic ids */
-	.probe		= vfio_pci_probe,
-	.remove		= vfio_pci_remove,
-	.err_handler	= &vfio_err_handlers,
+	.name			= "vfio-pci",
+	.id_table		= NULL, /* only dynamic ids */
+	.probe			= vfio_pci_probe,
+	.remove			= vfio_pci_remove,
+	.sriov_configure	= vfio_pci_sriov_configure,
+	.err_handler		= &vfio_err_handlers,
 };
 
 static DEFINE_MUTEX(reflck_lock);
diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
index 76c11c915949..36ec69081ecd 100644
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -13,6 +13,7 @@
 #include <linux/irqbypass.h>
 #include <linux/types.h>
 #include <linux/uuid.h>
+#include <linux/notifier.h>
 
 #ifndef VFIO_PCI_PRIVATE_H
 #define VFIO_PCI_PRIVATE_H
@@ -130,6 +131,7 @@ struct vfio_pci_device {
 	struct mutex		ioeventfds_lock;
 	struct list_head	ioeventfds_list;
 	struct vfio_pci_vf_token	*vf_token;
+	struct notifier_block	nb;
 };
 
 #define is_intx(vdev) (vdev->irq_type == VFIO_PCI_INTX_IRQ_INDEX)

Re: [PATCH v3 5/7] vfio/pci: Add sriov_configure support

[Cornelia Huck]

On Wed, 11 Mar 2020 15:59:12 -0600
Alex Williamson <alex.williamson@redhat.com> wrote:

> With the VF Token interface we can now expect that a vfio userspace
> driver must be in collaboration with the PF driver, an unwitting
> userspace driver will not be able to get past the GET_DEVICE_FD step
> in accessing the device.  We can now move on to actually allowing
> SR-IOV to be enabled by vfio-pci on the PF.  Support for this is not
> enabled by default in this commit, but it does provide a module option
> for this to be enabled (enable_sriov=1).  Enabling VFs is rather
> straightforward, except we don't want to risk that a VF might get
> autoprobed and bound to other drivers, so a bus notifier is used to
> "capture" VFs to vfio-pci using the driver_override support.  We
> assume any later action to bind the device to other drivers is
> condoned by the system admin and allow it with a log warning.
> 
> vfio-pci will disable SR-IOV on a PF before releasing the device,
> allowing a VF driver to be assured other drivers cannot take over the
> PF and that any other userspace driver must know the shared VF token.
> This support also does not provide a mechanism for the PF userspace
> driver itself to manipulate SR-IOV through the vfio API.  With this
> patch SR-IOV can only be enabled via the host sysfs interface and the
> PF driver user cannot create or remove VFs.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  drivers/vfio/pci/vfio_pci.c         |  106 +++++++++++++++++++++++++++++++----
>  drivers/vfio/pci/vfio_pci_private.h |    2 +
>  2 files changed, 97 insertions(+), 11 deletions(-)
> 

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

[PATCH v3 6/7] vfio/pci: Remove dev_fmt definition

[Alex Williamson]

It currently results in messages like:

 "vfio-pci 0000:03:00.0: vfio_pci: ..."

Which is quite a bit redundant.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/pci/vfio_pci.c |    1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index df6bae75c8dd..af1ba9867201 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -9,7 +9,6 @@
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-#define dev_fmt pr_fmt
 
 #include <linux/device.h>
 #include <linux/eventfd.h>

[PATCH v3 7/7] vfio/pci: Cleanup .probe() exit paths

[Alex Williamson]

The cleanup is getting a tad long.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/pci/vfio_pci.c |   54 ++++++++++++++++++++-----------------------
 1 file changed, 25 insertions(+), 29 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index af1ba9867201..6c6b37b5c04e 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -1598,8 +1598,8 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 
 	vdev = kzalloc(sizeof(*vdev), GFP_KERNEL);
 	if (!vdev) {
-		vfio_iommu_group_put(group, &pdev->dev);
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto out_group_put;
 	}
 
 	vdev->pdev = pdev;
@@ -1610,43 +1610,27 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	INIT_LIST_HEAD(&vdev->ioeventfds_list);
 
 	ret = vfio_add_group_dev(&pdev->dev, &vfio_pci_ops, vdev);
-	if (ret) {
-		vfio_iommu_group_put(group, &pdev->dev);
-		kfree(vdev);
-		return ret;
-	}
+	if (ret)
+		goto out_free;
 
 	ret = vfio_pci_reflck_attach(vdev);
-	if (ret) {
-		vfio_del_group_dev(&pdev->dev);
-		vfio_iommu_group_put(group, &pdev->dev);
-		kfree(vdev);
-		return ret;
-	}
+	if (ret)
+		goto out_del_group_dev;
 
 	if (pdev->is_physfn) {
 		vdev->vf_token = kzalloc(sizeof(*vdev->vf_token), GFP_KERNEL);
 		if (!vdev->vf_token) {
-			vfio_pci_reflck_put(vdev->reflck);
-			vfio_del_group_dev(&pdev->dev);
-			vfio_iommu_group_put(group, &pdev->dev);
-			kfree(vdev);
-			return -ENOMEM;
-		}
-
-		vdev->nb.notifier_call = vfio_pci_bus_notifier;
-		ret = bus_register_notifier(&pci_bus_type, &vdev->nb);
-		if (ret) {
-			kfree(vdev->vf_token);
-			vfio_pci_reflck_put(vdev->reflck);
-			vfio_del_group_dev(&pdev->dev);
-			vfio_iommu_group_put(group, &pdev->dev);
-			kfree(vdev);
-			return ret;
+			ret = -ENOMEM;
+			goto out_reflck;
 		}
 
 		mutex_init(&vdev->vf_token->lock);
 		uuid_gen(&vdev->vf_token->uuid);
+
+		vdev->nb.notifier_call = vfio_pci_bus_notifier;
+		ret = bus_register_notifier(&pci_bus_type, &vdev->nb);
+		if (ret)
+			goto out_vf_token;
 	}
 
 	if (vfio_pci_is_vga(pdev)) {
@@ -1672,6 +1656,18 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	}
 
 	return ret;
+
+out_vf_token:
+	kfree(vdev->vf_token);
+out_reflck:
+	vfio_pci_reflck_put(vdev->reflck);
+out_del_group_dev:
+	vfio_del_group_dev(&pdev->dev);
+out_free:
+	kfree(vdev);
+out_group_put:
+	vfio_iommu_group_put(group, &pdev->dev);
+	return ret;
 }
 
 static void vfio_pci_remove(struct pci_dev *pdev)

Re: [PATCH v3 7/7] vfio/pci: Cleanup .probe() exit paths

[Cornelia Huck]

On Wed, 11 Mar 2020 15:59:27 -0600
Alex Williamson <alex.williamson@redhat.com> wrote:

> The cleanup is getting a tad long.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  drivers/vfio/pci/vfio_pci.c |   54 ++++++++++++++++++++-----------------------
>  1 file changed, 25 insertions(+), 29 deletions(-)

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

RE: [PATCH v3 0/7] vfio/pci: SR-IOV support

[Tian, Kevin]

> From: Alex Williamson <alex.williamson@redhat.com>
> Sent: Thursday, March 12, 2020 5:58 AM
> 
> Only minor tweaks since v2, GET and SET on VFIO_DEVICE_FEATURE are
> enforced mutually exclusive except with the PROBE option as suggested
> by Connie, the modinfo text has been expanded for the opt-in to enable
> SR-IOV support in the vfio-pci driver per discussion with Kevin.
> 
> I have not incorporated runtime warnings attempting to detect misuse
> of SR-IOV or imposed a session lifetime of a VF token, both of which
> were significant portions of the discussion of the v2 series.  Both of
> these also seem to impose a usage model or make assumptions about VF
> resource usage or configuration requirements that don't seem necessary
> except for the sake of generating a warning or requiring an otherwise
> unnecessary and implicit token reinitialization.  If there are new
> thoughts around these or other discussion points, please raise them.
> 
> Series overview (same as provided with v1):
> 
> The synopsis of this series is that we have an ongoing desire to drive
> PCIe SR-IOV PFs from userspace with VFIO.  There's an immediate need
> for this with DPDK drivers and potentially interesting future use
> cases in virtualization.  We've been reluctant to add this support
> previously due to the dependency and trust relationship between the
> VF device and PF driver.  Minimally the PF driver can induce a denial
> of service to the VF, but depending on the specific implementation,
> the PF driver might also be responsible for moving data between VFs
> or have direct access to the state of the VF, including data or state
> otherwise private to the VF or VF driver.
> 
> To help resolve these concerns, we introduce a VF token into the VFIO
> PCI ABI, which acts as a shared secret key between drivers.  The
> userspace PF driver is required to set the VF token to a known value
> and userspace VF drivers are required to provide the token to access
> the VF device.  If a PF driver is restarted with VF drivers in use, it
> must also provide the current token in order to prevent a rogue
> untrusted PF driver from replacing a known driver.  The degree to
> which this new token is considered secret is left to the userspace
> drivers, the kernel intentionally provides no means to retrieve the
> current token.
> 
> Note that the above token is only required for this new model where
> both the PF and VF devices are usable through vfio-pci.  Existing
> models of VFIO drivers where the PF is used without SR-IOV enabled
> or the VF is bound to a userspace driver with an in-kernel, host PF
> driver are unaffected.
> 
> The latter configuration above also highlights a new inverted scenario
> that is now possible, a userspace PF driver with in-kernel VF drivers.
> I believe this is a scenario that should be allowed, but should not be
> enabled by default.  This series includes code to set a default
> driver_override for VFs sourced from a vfio-pci user owned PF, such
> that the VFs are also bound to vfio-pci.  This model is compatible
> with tools like driverctl and allows the system administrator to
> decide if other bindings should be enabled.  The VF token interface
> above exists only between vfio-pci PF and VF drivers, once a VF is
> bound to another driver, the administrator has effectively pronounced
> the device as trusted.  The vfio-pci driver will note alternate
> binding in dmesg for logging and debugging purposes.
> 
> Please review, comment, and test.  The example QEMU implementation
> provided with the RFC is still current for this version.  Thanks,
> 
> Alex

The whole series looks good to me:
	Reviewed-by: Kevin Tian <kevin.tian@intel.com>

and confirm one understanding here, since it is not discussed anywhere. For
VM live migration with assigned VF device, it is not necessary to migrate the
VF token itself and actually we don't allow userspace to retrieve it. Instead,
Qemu just follows whatever token requirement on the dest to open the new
VF: could be same or different token as/from src, or even no token if PF
driver runs in kernel on dest. I suppose either combination could work, correct?

Thanks
Kevin

> 
> RFC:
> https://lore.kernel.org/lkml/158085337582.9445.17682266437583505502.stg
> it@gimli.home/
> v1:
> https://lore.kernel.org/lkml/158145472604.16827.15751375540102298130.st
> git@gimli.home/
> v2:
> https://lore.kernel.org/lkml/158213716959.17090.8399427017403507114.stg
> it@gimli.home/
> 
> ---
> 
> Alex Williamson (7):
>       vfio: Include optional device match in vfio_device_ops callbacks
>       vfio/pci: Implement match ops
>       vfio/pci: Introduce VF token
>       vfio: Introduce VFIO_DEVICE_FEATURE ioctl and first user
>       vfio/pci: Add sriov_configure support
>       vfio/pci: Remove dev_fmt definition
>       vfio/pci: Cleanup .probe() exit paths
> 
> 
>  drivers/vfio/pci/vfio_pci.c         |  390
> +++++++++++++++++++++++++++++++++--
>  drivers/vfio/pci/vfio_pci_private.h |   10 +
>  drivers/vfio/vfio.c                 |   20 +-
>  include/linux/vfio.h                |    4
>  include/uapi/linux/vfio.h           |   37 +++
>  5 files changed, 433 insertions(+), 28 deletions(-)

Re: [PATCH v3 0/7] vfio/pci: SR-IOV support

[Alex Williamson]

On Thu, 19 Mar 2020 06:32:25 +0000
"Tian, Kevin" <kevin.tian@intel.com> wrote:

> > From: Alex Williamson <alex.williamson@redhat.com>
> > Sent: Thursday, March 12, 2020 5:58 AM
> > 
> > Only minor tweaks since v2, GET and SET on VFIO_DEVICE_FEATURE are
> > enforced mutually exclusive except with the PROBE option as suggested
> > by Connie, the modinfo text has been expanded for the opt-in to enable
> > SR-IOV support in the vfio-pci driver per discussion with Kevin.
> > 
> > I have not incorporated runtime warnings attempting to detect misuse
> > of SR-IOV or imposed a session lifetime of a VF token, both of which
> > were significant portions of the discussion of the v2 series.  Both of
> > these also seem to impose a usage model or make assumptions about VF
> > resource usage or configuration requirements that don't seem necessary
> > except for the sake of generating a warning or requiring an otherwise
> > unnecessary and implicit token reinitialization.  If there are new
> > thoughts around these or other discussion points, please raise them.
> > 
> > Series overview (same as provided with v1):
> > 
> > The synopsis of this series is that we have an ongoing desire to drive
> > PCIe SR-IOV PFs from userspace with VFIO.  There's an immediate need
> > for this with DPDK drivers and potentially interesting future use
> > cases in virtualization.  We've been reluctant to add this support
> > previously due to the dependency and trust relationship between the
> > VF device and PF driver.  Minimally the PF driver can induce a denial
> > of service to the VF, but depending on the specific implementation,
> > the PF driver might also be responsible for moving data between VFs
> > or have direct access to the state of the VF, including data or state
> > otherwise private to the VF or VF driver.
> > 
> > To help resolve these concerns, we introduce a VF token into the VFIO
> > PCI ABI, which acts as a shared secret key between drivers.  The
> > userspace PF driver is required to set the VF token to a known value
> > and userspace VF drivers are required to provide the token to access
> > the VF device.  If a PF driver is restarted with VF drivers in use, it
> > must also provide the current token in order to prevent a rogue
> > untrusted PF driver from replacing a known driver.  The degree to
> > which this new token is considered secret is left to the userspace
> > drivers, the kernel intentionally provides no means to retrieve the
> > current token.
> > 
> > Note that the above token is only required for this new model where
> > both the PF and VF devices are usable through vfio-pci.  Existing
> > models of VFIO drivers where the PF is used without SR-IOV enabled
> > or the VF is bound to a userspace driver with an in-kernel, host PF
> > driver are unaffected.
> > 
> > The latter configuration above also highlights a new inverted scenario
> > that is now possible, a userspace PF driver with in-kernel VF drivers.
> > I believe this is a scenario that should be allowed, but should not be
> > enabled by default.  This series includes code to set a default
> > driver_override for VFs sourced from a vfio-pci user owned PF, such
> > that the VFs are also bound to vfio-pci.  This model is compatible
> > with tools like driverctl and allows the system administrator to
> > decide if other bindings should be enabled.  The VF token interface
> > above exists only between vfio-pci PF and VF drivers, once a VF is
> > bound to another driver, the administrator has effectively pronounced
> > the device as trusted.  The vfio-pci driver will note alternate
> > binding in dmesg for logging and debugging purposes.
> > 
> > Please review, comment, and test.  The example QEMU implementation
> > provided with the RFC is still current for this version.  Thanks,
> > 
> > Alex  
> 
> The whole series looks good to me:
> 	Reviewed-by: Kevin Tian <kevin.tian@intel.com>

Thanks!

> and confirm one understanding here, since it is not discussed anywhere. For
> VM live migration with assigned VF device, it is not necessary to migrate the
> VF token itself and actually we don't allow userspace to retrieve it. Instead,
> Qemu just follows whatever token requirement on the dest to open the new
> VF: could be same or different token as/from src, or even no token if PF
> driver runs in kernel on dest. I suppose either combination could work, correct?

That's correct.  Thanks,

Alex

> > RFC:
> > https://lore.kernel.org/lkml/158085337582.9445.17682266437583505502.stg
> > it@gimli.home/
> > v1:
> > https://lore.kernel.org/lkml/158145472604.16827.15751375540102298130.st
> > git@gimli.home/
> > v2:
> > https://lore.kernel.org/lkml/158213716959.17090.8399427017403507114.stg
> > it@gimli.home/
> > 
> > ---
> > 
> > Alex Williamson (7):
> >       vfio: Include optional device match in vfio_device_ops callbacks
> >       vfio/pci: Implement match ops
> >       vfio/pci: Introduce VF token
> >       vfio: Introduce VFIO_DEVICE_FEATURE ioctl and first user
> >       vfio/pci: Add sriov_configure support
> >       vfio/pci: Remove dev_fmt definition
> >       vfio/pci: Cleanup .probe() exit paths
> > 
> > 
> >  drivers/vfio/pci/vfio_pci.c         |  390
> > +++++++++++++++++++++++++++++++++--
> >  drivers/vfio/pci/vfio_pci_private.h |   10 +
> >  drivers/vfio/vfio.c                 |   20 +-
> >  include/linux/vfio.h                |    4
> >  include/uapi/linux/vfio.h           |   37 +++
> >  5 files changed, 433 insertions(+), 28 deletions(-)  
>