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

Alex Williamson
2020-02-11T23:06:11Z

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. With this patch SR-IOV can only
be enabled via the host sysfs interface and the PF driver user cannot
create and remove VF.

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 5414744a3ead..cce6127a9c56 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");
+#endif
+
static inline bool vfio_vga_disabled(void)
{
#ifdef CONFIG_VFIO_PCI_VGA
@@ -1457,6 +1463,35 @@ 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)
{
@@ -1468,12 +1503,12 @@ 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");
@@ -1521,6 +1556,18 @@ 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);
}
@@ -1554,6 +1601,8 @@ 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;
@@ -1564,6 +1613,9 @@ 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);
@@ -1612,16 +1664,48 @@ 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 6da2b4748abf..b651a007334d 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)