Peter Maydell <peter.mayd...@linaro.org> writes: > On Mon, 7 Oct 2019 at 11:50, Markus Armbruster <arm...@redhat.com> wrote: >> Peter Maydell <peter.mayd...@linaro.org> writes: >> > Basically new submodules are a pain so we seek to minimize >> > the use of them. >> >> I suggested making it a submodule upthread[*]. Let me try to distill >> the conversation into a rationale. Giuseppe, please correct mistakes. >> >> To make use of QEMU's netmap backend (CONFIG_NETMAP), you have to build >> and install netmap software from sources[**]. Which pretty much ensures >> developers compile with CONFIG_NETMAP off, and the code rots. >> >> For other dependencies that aren't readily available on common >> development hosts (slirp, capstone), we use submodules to avoid such >> rot. If the system provides, we use that, and if it doesn't, we fall >> back to the submodule. This has served us well. > > I would put this differently. We don't use submodules to avoid > code-rot. We use submodules where a dependency is needed for us > to provide QEMU features that are sufficiently important that we > want to provide them to users even if those users don't have the > dependency available to them as a system library. > > There are lots of features of QEMU that only compile with sufficiently > recent versions of dependencies, and we don't try to submodule-ize > them because the features aren't really that important for the bulk > of our users. For instance, we provided pixman as a submodule for > a while because the features that require it (our graphics layer > code) are important to almost all users. But we didn't provide > spice as a module even when you pretty much needed to be > running bleeding-edge redhat to satisfy the version dependency > we had, because most users don't care about spice support. > Shipping our dependencies as submodules imposes real costs > on the project (for instance we then need to track the upstream > to see when we should be updating, including checking whether > we need to update to fix security issues). Submodules should be > the exception, not the rule. > >> For netmap, falling back to the submodule when the host doesn't provide >> tends not to be useful beyond compile-testing. Because of that, we fall >> back only when the user explicitly asks for it by passing >> --enable-netmap=git to configure. CI should do that. > > This sounds like netmap is in the same position as most of our > dependencies: OK to compile if the system provides the library, > but if the system doesn't then almost all users won't care > that the feature isn't present. If CI of the QEMU code is useful,
If CI of QEMU code isn't useful, then I suspect the QEMU code isn't useful, period. Giuseppe assures us the netmap QEMU code *is* useful. It followe we better make sure our CI covers it. A submodule would make sure, but it looks like it won't fly. So let's try another tack: > get the library supported by and shipped in distros. If you can't > get anybody in a distro (Linux or BSD) to care enough to ship the > library, this is a really niche feature, and up for consideration > for deprecate-and-drop from QEMU, I think. Giuseppe, you mentioned netmap is in FreeBSD, and getting it into Linux is unlikely, so let's focus on FreeBSD. We have a FreeBSD section in .patchew.yml, which makes me guess Patchew CI tests FreeBSD. Does it test with CONFIG_NETMAP out of the box? If not, how do we have to tweak its configuration to get CONFIG_NETMAP enabled? Who could help with this?
