On Tue, Mar 14, 2023 at 03:47:43AM +0000, Parav Pandit wrote: > > > From: Michael S. Tsirkin <mst@xxxxxxxxxx> > > Sent: Monday, March 13, 2023 11:38 PM > > > > On Tue, Mar 14, 2023 at 02:05:50AM +0000, Parav Pandit wrote: > > > > > > > From: Si-Wei Liu <si-wei.liu@xxxxxxxxxx> > > > > Sent: Monday, March 13, 2023 6:19 PM > > > > > > > Actually there's no such burden or requirement to maintain backward > > > > compatibility for the default 'vdpa dev add' behavior if dedicated > > > > device_features is not specified. Historically the default vdpa > > > > creation on mlx5 ever got changed from single queue to 8 queue pairs > > > > when VIRTIO_NET_F_MQ feature was first introduced to mlx5_vdpa, then > > > > the default switched back to 1 data queue pair again when max_vqp > > attribute was added to the vdpa tool. > > > > Essentially, every addition of new feature to mlx5_vdpa, e.g. > > > > CTRL_VQ, CTRL_VLAN, and et al, effectively changed the default "vdpa > > > > dev add" behavior not just only once: the backward compatibility > > > > guarantee is simply just not there and ever. > > > This requires that every change in the device attributes will change the > > behavior for vdpa dev add. > > > The OR operation of the user supplied feature bits with device defaults > > feature bit doesn’t look good to me. > > > It brings uncertain behavior. > > > > > > The right behavior should be, if user supplied the feature bits, it should > > supply all desired bits. > > > > I think u mean all that device also supports. > > > If user supplied feature bits and device doesn’t support some of the feature bits -> add command fails. > If user supplied feature bits, than use only the feature bits. Do not OR user supplied feature bits with device supported feature bits. > For example, > User asked to set, > F_CONFIG_MTU > F_CONFIG_MAC > F_PACKED > In that device should only use above 3 features. (because user is the master). > > It should not OR user supplied feature bits with device defaults feature bits. > > > > If user doesn’t supply feature bits, use the device defaults. > > If user doesn’t supply any feature fits, that means user wants to run with some device defaults. > In that case its fine to run with device defaults. But this is not what this patch does? > > > But not to mix both feature bits. > > > > Can't say I understand what this means. What does "both" mean here? > > Mix Both means, to perform OR operation on user supplied feature bits with device defaults. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
