| Message ID | 1565926427-21675-1-git-send-email-hexin15@baidu.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | 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 | expand |
On Fri, 16 Aug 2019 11:33:47 +0800 hexin <hexin.op@gmail.com> wrote: > 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@baidu.com> > Signed-off-by: Liu Qi <liuqi16@baidu.com> > Signed-off-by: Zhang Yu <zhangyu31@baidu.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: This used to work, I think what happened is that we initially called __pci_reset_function() to avoid the saved state getting overwritten, then commit d24cdbfd28b7 ("vfio-pci: Avoid deadlock on remove") added the trylock support to avoid deadlock, then commit 890ed578df82 ("vfio-pci: Use pci "try" reset interface") assumed the trylock was the reason for the unusual calling convention and simply replaced it with pci_try_reset_function(). So, I think we need two things. First, a fixes tag: Fixes: 890ed578df82 ("vfio-pci: Use pci "try" reset interface") Second, a comment to warn us against performing a similar cleanup again in the future. Thanks, Alex
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: