[kvm-unit-tests] riscv build failure

[Andrew Jones]

On Thu, Sep 04, 2025 at 08:57:54AM +0930, Joel Stanley wrote:
> I'm building kvm-unit-tests as part of buildroot and hitting a build
> failure. It looks like there's a missing dependency on
> riscv/sbi-asm.S, as building that manually fixes the issue. Triggering
> buildroot again (several times) doesn't resolve the issue so it
> doesn't look like a race condition.
> 
> I can't reproduce with a normal cross compile on my machine. Buildroot
> uses make -C, in case that makes a difference.
> 
> The build steps look like this:
> 
> bzcat /localdev/jms/buildroot/dl/kvm-unit-tests/kvm-unit-tests-v2025-06-05.tar.bz2
> | /localdev/jms/buildroot/output-riscv-rvv/host/bin/tar
> --strip-components=1 -C
> /localdev/jms/buildroot/output-riscv-rvv/build/kvm-unit-tests-2025-06-05
>   -xf -
> cd /localdev/jms/buildroot/output-riscv-rvv/build/kvm-unit-tests-2025-06-05
> && ./configure --disable-werror --arch="riscv64" --processor=""
> --endian="little"
> --cross-prefix="/localdev/jms/buildroot/output-riscv-rvv/host/bin/riscv64-buildroot-linux-gnu-"
> GIT_DIR=. PATH="/localdev/jms/buildroot/output-riscv-rvv/host/bin:/localdev/jms/buildroot/output-riscv-rvv/host/sbin:/home/jms/.local/bin:/home/jms/bin:/home/jms/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin"
> /usr/bin/make -j385  -C
> /localdev/jms/buildroot/output-riscv-rvv/build/kvm-unit-tests-2025-06-05
> standalone

I applied similar steps but couldn't reproduce this. It also looks like we
have a dependency because configuring with '--cc=/path/to/mygcc', where
mygcc is

   #!/bin/bash
   for x in $@; do
       if [[ $x =~ sbi-asm ]] && ! [[ $x =~ sbi-asm-offsets ]]; then
           sleep 5
           break
       fi
   done
   /path/to/riscv64-linux-gnu-gcc $@

stalls the build 5 seconds when compiling sbi-asm.S but doesn't reproduce
the issue. That said, running make with -d shows that riscv/sbi-asm.o is
an implicit prerequisite, although so are other files. I'm using
GNU Make 4.4.1. Which version are you using?

Also, while the steps above shouldn't cause problems, they are a bit odd
 * '--endian' only applies to ppc64
 * -j385 is quite large and specific. Typicall -j$(nproc) is recommended.
 * No need for '-C "$PWD"'

Thanks,
drew