[PATCH] vfio-pci: Attempt bus/slot reset on open

From: Alex Williamson
Date: Thu Apr 09 2015 - 11:55:29 EST

Apply the same logic we use in vfio_pci_try_bus_reset() to perform a
bus or slot reset as devices are released to the device open path.
This not only improves our chances of handing the device to the user
in a clean state, but we can also avoid duplicate resets if the device
is released and re-opened while bound to vfio-pci. We can also
potentially reset multiple device with a single bus/slot reset and
avoid multiple function-level resets later. We switch to using
pci_probe_reset_function() since we still want to expose function
level reset to the user, but we may not use it as the reset mechanism
of choice when enabling the device.

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

Depends on export of pci_probe_reset_function()

drivers/vfio/pci/vfio_pci.c | 24 +++++++++++++++++++++---
1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 69fab0f..d9f7ec5 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -119,16 +119,32 @@ static int vfio_pci_enable(struct vfio_pci_device *vdev)
u16 cmd;
u8 msix_pos;

- pci_set_power_state(pdev, PCI_D0);
+ /*
+ * Start by resetting the device(s). A bus reset is our best method
+ * and may not be available once other devices are in use. It may
+ * also mark multiple devices as clean, avoiding duplicate function
+ * level resets later.
+ */
+ vfio_pci_try_bus_reset(vdev);
+ if (vdev->needs_reset)
+ vdev->needs_reset = !(pci_try_reset_function(pdev) == 0);

- /* Don't allow our initial saved state to include busmaster */
+ /*
+ * These are reset defaults, but let's be sure the device is awake
+ * and not doing DMA. We do not want BusMaster enabled in save state.
+ */
+ pci_set_power_state(pdev, PCI_D0);

+ /* Initialize device */
ret = pci_enable_device(pdev);
if (ret)
return ret;

- vdev->reset_works = (pci_reset_function(pdev) == 0);
+ /*
+ * Checkpoint, this is the base level state we want to
+ * restore when the device is released.
+ */
vdev->pci_saved_state = pci_store_saved_state(pdev);
if (!vdev->pci_saved_state)
@@ -948,6 +964,8 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
vdev->irq_type = VFIO_PCI_NUM_IRQS;
+ vdev->reset_works = (pci_probe_reset_function(pdev) == 0);
+ vdev->needs_reset = true;

ret = vfio_add_group_dev(&pdev->dev, &vfio_pci_ops, vdev);
if (ret) {

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