Si-Wei Liu
2021-Feb-09 01:40 UTC
[PATCH 3/3] mlx5_vdpa: defer clear_virtqueues to until DRIVER_OK
On 2/7/2021 9:48 PM, Eli Cohen wrote:> On Sat, Feb 06, 2021 at 04:29:24AM -0800, Si-Wei Liu wrote: >> While virtq is stopped, get_vq_state() is supposed to >> be called to get sync'ed with the latest internal >> avail_index from device. The saved avail_index is used >> to restate the virtq once device is started. Commit >> b35ccebe3ef7 introduced the clear_virtqueues() routine >> to reset the saved avail_index, however, the index >> gets cleared a bit earlier before get_vq_state() tries >> to read it. This would cause consistency problems when >> virtq is restarted, e.g. through a series of link down >> and link up events. We could defer the clearing of >> avail_index to until the device is to be started, >> i.e. until VIRTIO_CONFIG_S_DRIVER_OK is set again in >> set_status(). > > Not sure I understand the scenario. You are talking about reset of the > device followed by up/down events on the interface. How can you trigger > this?Currently it's not possible to trigger link up/down events with upstream QEMU due lack of config/control interrupt implementation. And live migration could be another scenario that cannot be satisfied because of inconsistent queue state. They share the same root of cause as captured here. -Siwei> >> Fixes: b35ccebe3ef7 ("vdpa/mlx5: Restore the hardware used index after change map") >> Signed-off-by: Si-Wei Liu <si-wei.liu at oracle.com> >> --- >> drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c >> index aa6f8cd..444ab58 100644 >> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c >> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c >> @@ -1785,7 +1785,6 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status) >> if (!status) { >> mlx5_vdpa_info(mvdev, "performing device reset\n"); >> teardown_driver(ndev); >> - clear_virtqueues(ndev); >> mlx5_vdpa_destroy_mr(&ndev->mvdev); >> ndev->mvdev.status = 0; >> ++mvdev->generation; >> @@ -1794,6 +1793,7 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status) >> >> if ((status ^ ndev->mvdev.status) & VIRTIO_CONFIG_S_DRIVER_OK) { >> if (status & VIRTIO_CONFIG_S_DRIVER_OK) { >> + clear_virtqueues(ndev); >> err = setup_driver(ndev); >> if (err) { >> mlx5_vdpa_warn(mvdev, "failed to setup driver\n"); >> -- >> 1.8.3.1 >>