vfio-pci: Attempt bus/slot reset on release

Each time a device is released, mark whether a local reset was
successful or whether a bus/slot reset is needed.  If a reset is
needed and all of the affected devices are bound to vfio-pci and
unused, allow the reset.  This is most useful when the userspace
driver is killed and releases all the devices in an unclean state,
such as when a QEMU VM quits.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index c9d756b7ee9eb83a2865e2c5c8b6f31691a2f454..1651c0769b728905ba759a87f0d1d3efcc2adcf7 100644 (file)
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -39,6 +39,8 @@ MODULE_PARM_DESC(nointxmask,
 
 static DEFINE_MUTEX(driver_lock);
 
+static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev);
+
 static int vfio_pci_enable(struct vfio_pci_device *vdev)
 {
        struct pci_dev *pdev = vdev->pdev;
@@ -123,6 +125,8 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
                vdev->barmap[bar] = NULL;
        }
 
+       vdev->needs_reset = true;
+
        /*
         * If we have saved state, restore it.  If we can reset the device,
         * even better.  Resetting with current state seems better than
@@ -154,11 +158,15 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
                if (ret)
                        pr_warn("%s: Failed to reset device %s (%d)\n",
                                __func__, dev_name(&pdev->dev), ret);
+               else
+                       vdev->needs_reset = false;
        }
 
        pci_restore_state(pdev);
 out:
        pci_disable_device(pdev);
+
+       vfio_pci_try_bus_reset(vdev);
 }
 
 static void vfio_pci_release(void *device_data)
@@ -923,6 +931,110 @@ static struct pci_driver vfio_pci_driver = {
        .err_handler    = &vfio_err_handlers,
 };
 
+/*
+ * Test whether a reset is necessary and possible.  We mark devices as
+ * needs_reset when they are released, but don't have a function-local reset
+ * available.  If any of these exist in the affected devices, we want to do
+ * a bus/slot reset.  We also need all of the affected devices to be unused,
+ * so we abort if any device has a non-zero refcnt.  driver_lock prevents a
+ * device from being opened during the scan or unbound from vfio-pci.
+ */
+static int vfio_pci_test_bus_reset(struct pci_dev *pdev, void *data)
+{
+       bool *needs_reset = data;
+       struct pci_driver *pci_drv = ACCESS_ONCE(pdev->driver);
+       int ret = -EBUSY;
+
+       if (pci_drv == &vfio_pci_driver) {
+               struct vfio_device *device;
+               struct vfio_pci_device *vdev;
+
+               device = vfio_device_get_from_dev(&pdev->dev);
+               if (!device)
+                       return ret;
+
+               vdev = vfio_device_data(device);
+               if (vdev) {
+                       if (vdev->needs_reset)
+                               *needs_reset = true;
+
+                       if (!vdev->refcnt)
+                               ret = 0;
+               }
+
+               vfio_device_put(device);
+       }
+
+       /*
+        * TODO: vfio-core considers groups to be viable even if some devices
+        * are attached to known drivers, like pci-stub or pcieport.  We can't
+        * freeze devices from being unbound to those drivers like we can
+        * here though, so it would be racy to test for them.  We also can't
+        * use device_lock() to prevent changes as that would interfere with
+        * PCI-core taking device_lock during bus reset.  For now, we require
+        * devices to be bound to vfio-pci to get a bus/slot reset on release.
+        */
+
+       return ret;
+}
+
+/* Clear needs_reset on all affected devices after successful bus/slot reset */
+static int vfio_pci_clear_needs_reset(struct pci_dev *pdev, void *data)
+{
+       struct pci_driver *pci_drv = ACCESS_ONCE(pdev->driver);
+
+       if (pci_drv == &vfio_pci_driver) {
+               struct vfio_device *device;
+               struct vfio_pci_device *vdev;
+
+               device = vfio_device_get_from_dev(&pdev->dev);
+               if (!device)
+                       return 0;
+
+               vdev = vfio_device_data(device);
+               if (vdev)
+                       vdev->needs_reset = false;
+
+               vfio_device_put(device);
+       }
+
+       return 0;
+}
+
+/*
+ * Attempt to do a bus/slot reset if there are devices affected by a reset for
+ * this device that are needs_reset and all of the affected devices are unused
+ * (!refcnt).  Callers of this function are required to hold driver_lock such
+ * that devices can not be unbound from vfio-pci or opened by a user while we
+ * test for and perform a bus/slot reset.
+ */
+static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev)
+{
+       bool needs_reset = false, slot = false;
+       int ret;
+
+       if (!pci_probe_reset_slot(vdev->pdev->slot))
+               slot = true;
+       else if (pci_probe_reset_bus(vdev->pdev->bus))
+               return;
+
+       if (vfio_pci_for_each_slot_or_bus(vdev->pdev,
+                                         vfio_pci_test_bus_reset,
+                                         &needs_reset, slot) || !needs_reset)
+               return;
+
+       if (slot)
+               ret = pci_try_reset_slot(vdev->pdev->slot);
+       else
+               ret = pci_try_reset_bus(vdev->pdev->bus);
+
+       if (ret)
+               return;
+
+       vfio_pci_for_each_slot_or_bus(vdev->pdev,
+                                     vfio_pci_clear_needs_reset, NULL, slot);
+}
+
 static void __exit vfio_pci_cleanup(void)
 {
        pci_unregister_driver(&vfio_pci_driver);

diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
index 31e7a30196ab463cf7d4214eae7d5b279694ab06..671c17a6e6d029dfdffe5d7243150ed757e44cf4 100644 (file)
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -54,6 +54,7 @@ struct vfio_pci_device {
        bool                    extended_caps;
        bool                    bardirty;
        bool                    has_vga;
+       bool                    needs_reset;
        struct pci_saved_state  *pci_saved_state;
        int                     refcnt;
        struct eventfd_ctx      *err_trigger;