If set, try legacy interface first, modern one if that fails. Useful to
work around device/driver bugs, and for compatibility testing.
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Tested-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
---
drivers/virtio/virtio_pci_common.c | 25 +++++++++++++++++++++----
1 file changed, 21 insertions(+), 4 deletions(-)
diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index 8ae34a3..e894eb2 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -19,6 +19,14 @@
#include "virtio_pci_common.h"
+static bool force_legacy = false;
+
+#if IS_ENABLED(CONFIG_VIRTIO_PCI_LEGACY)
+module_param(force_legacy, bool, 0444);
+MODULE_PARM_DESC(force_legacy,
+ "Force legacy mode for transitional virtio 1 devices");
+#endif
+
/* wait for pending irq handlers */
void vp_synchronize_vectors(struct virtio_device *vdev)
{
@@ -505,11 +513,20 @@ static int virtio_pci_probe(struct pci_dev *pci_dev,
if (rc)
goto err_request_regions;
- rc = virtio_pci_modern_probe(vp_dev);
- if (rc == -ENODEV)
+ if (force_legacy) {
rc = virtio_pci_legacy_probe(vp_dev);
- if (rc)
- goto err_probe;
+ /* Also try modern mode if we can't map BAR0 (no IO space). */
+ if (rc == -ENODEV || rc == -ENOMEM)
+ rc = virtio_pci_modern_probe(vp_dev);
+ if (rc)
+ goto err_probe;
+ } else {
+ rc = virtio_pci_modern_probe(vp_dev);
+ if (rc == -ENODEV)
+ rc = virtio_pci_legacy_probe(vp_dev);
+ if (rc)
+ goto err_probe;
+ }
pci_set_master(pci_dev);
--
MST
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