On Mon, Oct 30, 2017 at 06:30:56AM +0000, Ilya Lesokhin wrote: > > -----Original Message----- > > From: Michael S. Tsirkin [mailto:[email protected]] > > Sent: Monday, October 30, 2017 4:09 AM > > To: Ilya Lesokhin <[email protected]> > > Cc: [email protected]; > > [email protected] > > Subject: Re: packed ring layout proposal v3 > > > > On Sun, Oct 29, 2017 at 02:34:56PM +0000, Ilya Lesokhin wrote: > > > > -----Original Message----- > > > > From: Michael S. Tsirkin [mailto:[email protected]] > > > > Sent: Sunday, October 29, 2017 4:22 PM > > > > To: Ilya Lesokhin <[email protected]> > > > > Cc: [email protected]; > > > > [email protected] > > > > Subject: Re: packed ring layout proposal v3 > > > > > > > > If you do this whats the point of the id? Just use descriptor offset > > > > like virtio 0 > > did. > > > > > > > > > > I agree that ID is pointless when requests are completed in order. > > > > > > But I'm not sure what you mean by descriptor offset? > > > > Where the descriptor is within the ring. > > > > Using descriptor offset like virtio 0, won't work. > In virtio 0, there was no reordering in the descriptor ring, so the offset > was always unique. > In the new spec, if descriptor in offset 2 completes before the descriptor in > offset 1, > It can be put in offset 1, but reusing offset 1 is not yet safe. > > Also, please ignore my earlier comment about in-order completion, > It invalidates the entire discussion. > >
Yes, using offsets only works if all descriptors are used and written back in order. If they are, descriptor ID isn't necessary. If they aren't, it's necessary. -- MST _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
