On Mon, Feb 08, 2021 at 05:20:11PM -0800, Si-Wei Liu wrote: > > > On 2/7/2021 9:35 PM, Eli Cohen wrote: > > On Sat, Feb 06, 2021 at 04:29:23AM -0800, Si-Wei Liu wrote: > > > The mlx_features denotes the capability for which > > > set of virtio features is supported by device. In > > > principle, this field needs not be cleared during > > > virtio device reset, as this capability is static > > > and does not change across reset. > > > > > > In fact, the current code may have the assumption > > > that mlx_features can be reloaded from firmware > > > via the .get_features ops after device is reset > > > (via the .set_status ops), which is unfortunately > > > not true. The userspace VMM might save a copy > > > of backend capable features and won't call into > > > kernel again to get it on reset. This causes all > > > virtio features getting disabled on newly created > > > virtqs after device reset, while guest would hold > > > mismatched view of available features. For e.g., > > > the guest may still assume tx checksum offload > > > is available after reset and feature negotiation, > > > causing frames with bogus (incomplete) checksum > > > transmitted on the wire. > > > > > > Signed-off-by: Si-Wei Liu <si-wei.liu@xxxxxxxxxx> > > > --- > > > drivers/vdpa/mlx5/net/mlx5_vnet.c | 1 - > > > 1 file changed, 1 deletion(-) > > > > > > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c > > > index b8416c4..aa6f8cd 100644 > > > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c > > > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c > > > @@ -1788,7 +1788,6 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status) > > > clear_virtqueues(ndev); > > > mlx5_vdpa_destroy_mr(&ndev->mvdev); > > > ndev->mvdev.status = 0; > > > - ndev->mvdev.mlx_features = 0; > > > ++mvdev->generation; > > > return; > > > } > > Since we assume that device capabilities don't change, I think I would > > get the features through a call done in mlx5v_probe after the netdev > > object is created and change mlx5_vdpa_get_features() to just return > > ndev->mvdev.mlx_features. > Yep, it makes sense. Will post a revised patch. So I'm waiting for v2 of this patchset. Please make sure to post a cover letter with an overall description. > If vdpa tool allows > reconfiguration post probing, the code has to be reconciled then. > > > > > Did you actually see this issue in action? If you did, can you share > > with us how you trigerred this? > Issue is indeed seen in action. The mismatched tx-checksum offload as > described in the commit message was one of such examples. You would need a > guest reboot though (triggering device reset via the .set_status ops and > zero'ed mlx_features was loaded to deduce new actual_features for creating > the h/w virtq object) for repro. > > -Siwei > > > > > -- > > > 1.8.3.1 > > > _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
