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virtio_pci: add module param to force legacy mode

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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>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Michael S. Tsirkin 2015-01-15 17:54:13 +02:00 committed by Rusty Russell
parent 46506da5f3
commit ac399d8f39
1 changed files with 21 additions and 4 deletions
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25
drivers/virtio/virtio_pci_common.c
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@ -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);