On 03/29/2013 08:19 PM, Rusty Russell wrote: >> >> Shift count? > > You can only have 2^16 vqs per device. Is it verboten to write 16-bit > values to odd offsets? If so, we've just dropped it to 2^15 before you > have to do some decoding to do. Hard to care... > > I dislike saying "multiply offset by 2" because implementations will get > it wrong. That's because 0 will work either way, and that's going to be > the common case. > The main reason to use a shift count is that it lets the guest driver assume that the spacing is a power of two, requiring only shift, as opposed to an arbitrary number, requiring a multiply. It seems unlikely that there would be a legitimate reason for a non-power-of-two spacing between the VQ notifiers. The other reason is that if a particular host implementation needs separate pages for each notifier, that can be a pretty large number. -hpa _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
