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vfio/pci: Restore device state on PM transition

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PCI core handles save and restore of device state around reset, but
when using pci_set_power_state() we can unintentionally trigger a soft
reset of the device, where PCI core only restores the BAR state.  If
we're using vfio-pci's idle D3 support to try to put devices into low
power when unused, this might trigger a reset when the device is woken
for use.  Also power state management by the user, or within a guest,
can put the device into D3 power state with potentially limited
ability to restore the device if it should undergo a reset.  The PCI
spec does not define the extent of a soft reset and many devices
reporting soft reset on D3->D0 transition do not undergo a PCI config
space reset.  It's therefore assumed safe to unconditionally restore
the remainder of the state if the device indicates soft reset
support, even on a user initiated wakeup.

Implement a wrapper in vfio-pci to tag devices reporting PM reset
support, save their state on transitions into D3 and restore on
transitions back to D0.

Reported-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Alex Williamson
2019-02-09 13:43:30 -07:00
parent a390685589
commit 51ef3a004b
3 changed files with 70 additions and 9 deletions
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2
drivers/vfio/pci/vfio_pci_config.c
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@@ -691,7 +691,7 @@ static int vfio_pm_config_write(struct vfio_pci_device *vdev, int pos,
break;
}
pci_set_power_state(vdev->pdev, state);
vfio_pci_set_power_state(vdev, state);
}
return count;