Our current open/release path looks like this:
vfio_pci_open
vfio_pci_enable
pci_enable_device
pci_save_state
pci_store_saved_state
vfio_pci_release
vfio_pci_disable
pci_disable_device
pci_restore_state
pci_enable_device() doesn't modify PCI_COMMAND_MASTER, so if a device
comes to us with it enabled, it persists through the open and gets
stored as part of the device saved state. We then restore that saved
state when released, which can allow the device to attempt to continue
to do DMA. When the group is disconnected from the domain, this will
get caught by the IOMMU, but if there are other devices in the group,
the device may continue running and interfere with the user. Even in
the former case, IOMMUs don't necessarily behave well and a stream of
blocked DMA can result in unpleasant behavior on the host.
Explicitly disable Bus Master as we're enabling the device and
slightly re-work release to make sure that pci_disable_device() is
the last thing that touches the device.
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---
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 010e0f8..36d8332 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -44,6 +44,9 @@ static int vfio_pci_enable(struct vfio_pci_device *vdev)
u16 cmd;
u8 msix_pos;
+ /* Don't allow our initial saved state to include busmaster */
+ pci_clear_master(pdev);
+
ret = pci_enable_device(pdev);
if (ret)
return ret;
@@ -99,7 +102,8 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
struct pci_dev *pdev = vdev->pdev;
int bar;
- pci_disable_device(pdev);
+ /* Stop the device from further DMA */
+ pci_clear_master(pdev);
vfio_pci_set_irqs_ioctl(vdev, VFIO_IRQ_SET_DATA_NONE |
VFIO_IRQ_SET_ACTION_TRIGGER,
@@ -128,7 +132,7 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
__func__, dev_name(&pdev->dev));
if (!vdev->reset_works)
- return;
+ goto out;
pci_save_state(pdev);
}
@@ -151,6 +155,8 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
}
pci_restore_state(pdev);
+out:
+ pci_disable_device(pdev);
}
static void vfio_pci_release(void *device_data)
--
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