On Tue, Oct 15, 2024 at 03:17:18PM +0200, Paolo Bonzini wrote: > On top of this, the required version of bindgen is still too new > for Debian 12 and Ubuntu 22.04. This is fixed by the last four patches. > > This is an RFC for two reasons. First, because it would be a valid > decision to delay enabling of Rust until at least some of these > features are available in all supported distros.
Lets say we maximise our back compatibility today, and have to carry some sub-optimal code patterns. 1, 2, 3, 4 years down the lines, we can gradually eliminate those undesired code patterns / workarounds, as older distros naturally age-out of our matrix. After 4 years our entire matrix will have cycled, so we're not needing to carry this debt for very long (4 years is not long in the context of a project like QEMU which has been going several decades) IOW, we're deciding between * creating a bit of rust technical debt in the immediate term, in order to enable rust by default sooner vs * avoiding Rust technical debt, but delaying ability to enable rust by default. We could consider all C code to be technical debt though, and if we don't have Rust by default we'll continue adding yet more C code. IOW, option is just moving the debt from Rust back to C, which is arguably worse on balance. Personally I tend towards quicker adoption of Rust, despite the need for short term workarounds, as they'll disappear again reasonably quickly. > Another possibility > could be to accept Rust 1.64.0 but require installing a newer bindgen > (0.66.x for example) on those two distros with an older release. How difficult is it to get newer 'bindgen' installed on these platforms ? The audience here is not so much distros trying to package new QEMU, as that's ony relevant for new distro, but rather it is end usrs/contributors building QEMU for themslves. Can it be done automagically in the same way we "do the right thing" with the 3rd party crates we depend on, or is bindgen special in some way that makes it more inconvenient for users ? > Second, > because the series is missing the CI updates to actually ensure that > these minimum versions keep working. On the last point, see https://lists.nongnu.org/archive/html/qemu-devel/2024-10/msg02688.html with that series, it should be just a matter of adding '--enable-rust' in a few key jobs. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
