On Fri, 30.09.16 16:45, Richard W.M. Jones (rjo...@redhat.com) wrote: > [This is only compile-tested, as our kernel doesn't (yet) have > enough configured features to run systemd, but I'll report back > when I get it running.] > > RISC-V is an open source ISA in development since 2010 at UCB. > For more information, see https://riscv.org/ > > I am adding RISC-V support to Fedora: > https://fedoraproject.org/wiki/Architectures/RISC-V > > There are three major variants of the architecture (32-, 64- and > 128-bit). The 128-bit variant is a paper exercise, but the other two > really exist in silicon. RISC-V is always little endian. > > On Linux, the default kernel uname(2) can return "riscv" for all > variants. However a patch was added recently which makes the kernel > return one of "riscv32" or "riscv64" (or in future "riscv128"). So > systemd should be prepared to handle any of "riscv", "riscv32", > "riscv64" or "riscv128". If the kernel returns "riscv" then you > need to use the pointer size in order to know the real variant. > > The Fedora/RISC-V kernel only ever returns "riscv64" since we're only > doing Fedora for 64 bit at the moment, and we've patched the kernel so > it doesn't return "riscv". > > As well as the major bitsize variants, there are also architecture > extensions. However I'm trying to ensure that uname(2) does *not* > return any other information about those in utsname.machine, so that > we don't end up with "riscv64abcde" nonsense. Instead those > extensions will be exposed in /proc/cpuinfo similar to how flags work > in x86. > > I should also note that __SIZEOF_POINTER__ is a GCC extension, but it > appears to be used already in systemd so I guess that's OK.
Any chance you can move this cover letter (or at least most of it into the commit itself? I think it would be great to have all of this in the commit). Also, if riscv128 is a paper excercise for now, then I'd prefer if this was left out of the current patch for now. I created a github PR from this: https://github.com/systemd/systemd/pull/4282 Would be good to follow up discussion there. Lennart -- Lennart Poettering, Red Hat _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
