linux-kernel - [PATCH] vfio_pci: Replace pci_try_reset_function() with __pci_reset_function_locked() to ensure that the pci device configuration space is restored to its original state

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Message-Id: <1565926427-21675-1-git-send-email-hexin15@baidu.com>
Date:   Fri, 16 Aug 2019 11:33:47 +0800
From:   hexin <hexin.op@...il.com>
To:     Alex Williamson <alex.williamson@...hat.com>, kvm@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     hexin <hexin15@...du.com>, Liu Qi <liuqi16@...du.com>,
        Zhang Yu <zhangyu31@...du.com>
Subject: [PATCH] vfio_pci: Replace pci_try_reset_function() with __pci_reset_function_locked() to ensure that the pci device configuration space is restored to its original state

In vfio_pci_enable(), save the device's initial configuration information
and then restore the configuration in vfio_pci_disable(). However, the
execution result is not the same. Since the pci_try_reset_function()
function saves the current state before resetting, the configuration
information restored by pci_load_and_free_saved_state() will be
overwritten. The __pci_reset_function_locked() function can be used
to prevent the configuration space from being overwritten.

Signed-off-by: hexin <hexin15@...du.com>
Signed-off-by: Liu Qi <liuqi16@...du.com>
Signed-off-by: Zhang Yu <zhangyu31@...du.com>
---
 drivers/vfio/pci/vfio_pci.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 703948c..3c93492 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -441,8 +441,14 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
 	 * Try to reset the device.  The success of this is dependent on
 	 * being able to lock the device, which is not always possible.
 	 */
-	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:
-- 
1.8.3.1