[PATCH] virtio_pci: add module param to force legacy mode
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2015-01-15 15:56:28
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Subsystem:
the rest, virtio core · Maintainers:
Linus Torvalds, "Michael S. Tsirkin", Jason Wang, Eugenio Pérez
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@redhat.com> --- drivers/virtio/virtio_pci_common.c | 31 +++++++++++++++++++++++++------ 1 file changed, 25 insertions(+), 6 deletions(-)
diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index 20c7638..0f87b99 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) {
@@ -505,13 +513,24 @@ 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) - return rc; + if (force_legacy) { + rc = virtio_pci_legacy_probe(vp_dev); + /* Also try modern mode if we can't map BAR0 (no IO space). */ + if (rc != -ENODEV && rc != -ENOMEM) + return rc; - rc = virtio_pci_legacy_probe(vp_dev); - if (rc) - goto err_probe; + rc = virtio_pci_modern_probe(vp_dev); + if (rc) + goto err_probe; + } else { + rc = virtio_pci_modern_probe(vp_dev); + if (rc != -ENODEV) + return rc; + + rc = virtio_pci_legacy_probe(vp_dev); + if (rc) + goto err_probe; + } pci_set_master(pci_dev);
--
MST