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* [PATCH v3] vfio_pci: Restore original state on release
@ 2019-08-22  3:35 hexin
  2019-08-23 20:45 ` Alex Williamson
  0 siblings, 1 reply; 2+ messages in thread
From: hexin @ 2019-08-22  3:35 UTC (permalink / raw)
  To: Alex Williamson, kvm, linux-pci, linux-kernel; +Cc: hexin, Liu Qi, Zhang Yu

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>
---
v2->v3:
- change commit log 
v1->v2:
- add fixes tag
- add comment to warn 

[1] https://lore.kernel.org/linux-pci/1565926427-21675-1-git-send-email-hexin15@baidu.com
[2] https://lore.kernel.org/linux-pci/1566042663-16694-1-git-send-email-hexin15@baidu.com

 drivers/vfio/pci/vfio_pci.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 703948c..0220616 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -438,11 +438,20 @@ 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:
-- 
1.8.3.1


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH v3] vfio_pci: Restore original state on release
  2019-08-22  3:35 [PATCH v3] vfio_pci: Restore original state on release hexin
@ 2019-08-23 20:45 ` Alex Williamson
  0 siblings, 0 replies; 2+ messages in thread
From: Alex Williamson @ 2019-08-23 20:45 UTC (permalink / raw)
  To: hexin; +Cc: kvm, linux-pci, linux-kernel, hexin, Liu Qi, Zhang Yu

On Thu, 22 Aug 2019 11:35:19 +0800
hexin <hexin.op@gmail.com> wrote:

> 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>
> ---

Applied to vfio next branch for v5.4.  Thanks,

Alex

> v2->v3:
> - change commit log 
> v1->v2:
> - add fixes tag
> - add comment to warn 
> 
> [1] https://lore.kernel.org/linux-pci/1565926427-21675-1-git-send-email-hexin15@baidu.com
> [2] https://lore.kernel.org/linux-pci/1566042663-16694-1-git-send-email-hexin15@baidu.com
> 
>  drivers/vfio/pci/vfio_pci.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index 703948c..0220616 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -438,11 +438,20 @@ 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:


^ permalink raw reply	[flat|nested] 2+ messages in thread

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2019-08-22  3:35 [PATCH v3] vfio_pci: Restore original state on release hexin
2019-08-23 20:45 ` Alex Williamson

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