On Tue, Dec 03, 2024 at 10:59:24AM +0100, Philippe Mathieu-Daudé wrote: > Hi Andrea, > > On 3/12/24 10:47, Andrea Bolognani wrote: > > Currently the script won't generate a configuration file that > > sets up qemu-user-riscv32 on riscv64, likely under the > > assumption that 64-bit RISC-V machines can natively run 32-bit > > I'm confused by the "machines" description used for user emulation.
It is referring to the host machines, being able (or not) to run 32-bit usermode code on 64-bit host kernel. > > > RISC-V code. > > > > However this functionality, while theoretically possible, in > > practice is missing from most commonly available RISC-V hardware > > and not enabled at the distro level. So qemu-user-riscv32 really > > is the only option to run riscv32 binaries on riscv64. > > We have definitions such ELF_ARCH/ELF_PLATFORM/ELF_MACHINE to > parse ELF header and select the best CPU / flags. Maybe RISC-V > lacks them? Is that relevant, as we're not runing QEMU code at all in the problematic scenario ? Currently the script below will skip generating a binfmt rule for riscv32, when on a riscv64 host. Thus qemu-riscv32 will never get called, and the kernel will try & fail to run riscv32 binaries natively. This change would make us generate riscv32 binfmt rules and thus use qemu-riscv32 on riscv64 hosts for linux-user. Separatley this from patch, we should also consider whether it is time to do the same for aarch64/arm7. If I look at this page: https://gpages.juszkiewicz.com.pl/arm-socs-table/arm-socs.html and sort by 'announced' to see msot recent CPUs first, then almost all of them have "NO" in the "aarch32 support" column. IOW, on modern aarch64 CPUs, qemu-arm is the only viable way to run 32-bit usermode binaries AFAICT, and suggests we ought to be creating a binfmt rule for that on aarch64 hosts. > BTW we should expose that for linux-user as target_arch_elf.h, > like bsd-user does, that would reduce all these #ifdef'ry in > linux-user/elfload.c... > > > > > Make riscv32 and riscv64 each its own family, so that the > > configuration file we need to make 32-on-64 userspace emulation > > work gets generated. > > Does this patch aim for 9.2? Otherwise FYI I'm working on unifying > 32/64-bit targets, maybe for 10.0... Well in Fedora we'll backport it to 9.2 at least, and from that POV I'd consider it stable-9.2 material if accepted here. > > Link: https://src.fedoraproject.org/rpms/qemu/pull-request/72 > > Thanks: David Abdurachmanov <davi...@rivosinc.com> > > Thanks: Daniel P. Berrangé <berra...@redhat.com> > > Signed-off-by: Andrea Bolognani <abolo...@redhat.com> > > --- > > scripts/qemu-binfmt-conf.sh | 7 ++----- > > 1 file changed, 2 insertions(+), 5 deletions(-) Reviewed-by: Daniel P. Berrangé <berra...@redhat.com> > > > > diff --git a/scripts/qemu-binfmt-conf.sh b/scripts/qemu-binfmt-conf.sh > > index 6ef9f118d9..e38b767c24 100755 > > --- a/scripts/qemu-binfmt-conf.sh > > +++ b/scripts/qemu-binfmt-conf.sh > > @@ -110,11 +110,11 @@ hppa_family=hppa > > > > riscv32_magic='\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xf3\x00' > > > > riscv32_mask='\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff' > > -riscv32_family=riscv > > +riscv32_family=riscv32 > > > > riscv64_magic='\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xf3\x00' > > > > riscv64_mask='\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff' > > -riscv64_family=riscv > > +riscv64_family=riscv64 > > > > xtensa_magic='\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x5e\x00' > > > > xtensa_mask='\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff' > > @@ -168,9 +168,6 @@ qemu_get_family() { > > sparc*) > > echo "sparc" > > ;; > > - riscv*) > > - echo "riscv" > > - ;; > > loongarch*) > > echo "loongarch" > > ;; > 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 :|
