vfio_pci: Restore original state on release

BugLink: https://bugs.launchpad.net/bugs/1848274
[ Upstream commit 92c8026854c25093946e0d7fe536fd9eac440f06 ]

vfio_pci_enable() saves the device's initial configuration information
with the intent that it is restored in vfio_pci_disable().  However,
the commit referenced in Fixes: below replaced the call to
__pci_reset_function_locked(), which is not wrapped in a state save
and restore, with pci_try_reset_function(), which overwrites the
restored device state with the current state before applying it to the
device.  Reinstate use of __pci_reset_function_locked() to return to
the desired behavior.

Fixes: 890ed578df82 ("vfio-pci: Use pci "try" reset interface")
Signed-off-by: hexin <hexin15@baidu.com>
Signed-off-by: Liu Qi <liuqi16@baidu.com>
Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 9b633b30e7f50282637c80e7b18134bca43c58aa..006d3f9ba4a0786c099e4772f88afbbeb581179a 100644 (file)
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -363,11 +363,20 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
        pci_write_config_word(pdev, PCI_COMMAND, PCI_COMMAND_INTX_DISABLE);
 
        /*
-        * Try to reset the device.  The success of this is dependent on
-        * being able to lock the device, which is not always possible.
+        * Try to get the locks ourselves to prevent a deadlock. The
+        * success of this is dependent on being able to lock the device,
+        * which is not always possible.
+        * We can not use the "try" reset interface here, which will
+        * overwrite the previously restored configuration information.
         */
-       if (vdev->reset_works && !pci_try_reset_function(pdev))
-               vdev->needs_reset = false;
+       if (vdev->reset_works && pci_cfg_access_trylock(pdev)) {
+               if (device_trylock(&pdev->dev)) {
+                       if (!__pci_reset_function_locked(pdev))
+                               vdev->needs_reset = false;
+                       device_unlock(&pdev->dev);
+               }
+               pci_cfg_access_unlock(pdev);
+       }
 
        pci_restore_state(pdev);
 out: