On Thu, Jun 25, 2026 at 8:51 PM Bryan O'Donoghue <[email protected]> wrote: > > On 25/06/2026 21:24, Brian Daniels wrote: > > I'm not an expert here, but taking a look at those files, the vast majority > > of > > those reserved fields appear to be padding to ensure the struct has 64-bit > > alignment, which matches the use here in virtio-media as well. > > > > virtio_pci appears to be the only device that explicitly states the > > reserved bytes are for future extensions. Unless there's a good a reason to > > expect a future use case where more space is needed, I would prefer to not > > add > > more at this time. > > I'm querying why just the one though ? Why not say four ? > > Perhaps something you could address in your commit log. >
Sure I can add a note in v5. But yeah the reason is the total struct needs to be 64-bit aligned. So it can't be an arbitrary number. And all the current reserved fields add the minimum number of bits to ensure the existing structs are 64-bit aligned. Adding more means extra bytes are transferred every exchange without adding any value, which is inefficient.
