Re: [PATCH 20/20] target/loongarch: Add linux-user emulation support

[Thomas Huth]

On 01/07/2021 03.07, maobibo wrote:
> 在 2021年06月30日 17:36, Alex Bennée 写道:
> > maobibo <maobibo@loongson.cn> writes:
> >
> > > 在 2021年06月29日 21:42, Peter Maydell 写道:
> > > > On Mon, 28 Jun 2021 at 13:05, Song Gao <gaosong@loongson.cn> wrote:
> > > > > Add files to linux-user/loongarch64
> > > > > Add file to default-configs
> > > > > Add loongarch to target/meson.build
> > > > >
> > > > > Signed-off-by: Song Gao <gaosong@loongson.cn>
> > > > > ---
> > > > >   MAINTAINERS                                        |   1 +
> > > > >   default-configs/targets/loongarch64-linux-user.mak |   4 +
> > > > >   include/elf.h                                      |   2 +
> > > > >   linux-user/elfload.c                               |  58 ++++
> > > > >   linux-user/loongarch64/cpu_loop.c                  | 177 ++++++++++++
> > > > >   linux-user/loongarch64/signal.c                    | 193 +++++++++++++
> > > > >   linux-user/loongarch64/sockbits.h                  |   1 +
> > > > >   linux-user/loongarch64/syscall_nr.h                | 307 +++++++++++++++++++++
> > > > >   linux-user/loongarch64/target_cpu.h                |  36 +++
> > > > >   linux-user/loongarch64/target_elf.h                |  14 +
> > > > >   linux-user/loongarch64/target_fcntl.h              |  12 +
> > > > >   linux-user/loongarch64/target_signal.h             |  28 ++
> > > > >   linux-user/loongarch64/target_structs.h            |  49 ++++
> > > > >   linux-user/loongarch64/target_syscall.h            |  46 +++
> > > > >   linux-user/loongarch64/termbits.h                  | 229 +++++++++++++++
> > > > >   linux-user/syscall_defs.h                          |   8 +-
> > > > >   meson.build                                        |   2 +-
> > > > >   qapi/machine-target.json                           |   4 +-
> > > > >   target/loongarch/meson.build                       |  19 ++
> > > > >   target/meson.build                                 |   1 +
> > > > >   20 files changed, 1185 insertions(+), 6 deletions(-)
> > > >
> > > > This is a massive patch that would benefit from being split up
> > > > into multiple smaller patches.
> > > >
> > > > I'm told by a kernel developer that loongarch hasn't yet been
> > > > accepted into the Linux kernel mainline. Until it has been, the
> > > > syscall ABI for it is not yet stable, so we won't be able to take
> > > > the linux-user patches for it yet. (We have been burned in the
> > > > past by taking linux-user architecture support patches without
> > > > realizing they weren't for a stable ABI, and then being out of
> > > > sync with the eventual upstream kernel ABI that was accepted.)
> > > >
> > > > We can certainly do code review in the meantime, though.
> > > Thanks for reviewing the big series patches. It is understandable that
> > > there should be linux kernel merged for one new architecture support
> > > firstly, and then there will be linux-user simulator later.
> > >
> > > We are planning to submit patch to linux kernel for LoongArch support,
> > > there is the link:
> > > https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson.git/log/?h=loongarch-next
> > >
> > > And we will continueto  submit softmmu support for LoongArch. And is there
> > > any extra requirements for softmmu simulation for new architecture,
> > > such as gcc/binutils/bios?
> >
> > Ideally if there are some pre-built toolchains either as part of a
> > distro (we've used Debian Sid before for some) or easily to install in a
> > docker container as binary tarballs (like we do for tricore) then we can
> > enable basic check-tcg functionality.
> >
> > Going forward having stable URLs for test images of distros means we can
> > also enable check-acceptance tests.
> Thanks for guidance, it requires that linux kernel/gcc/glibc are submitted
> already. My meaning is that linux-user emulation depends on kernel
> syscall ABI, softmmu emulation does not have such dependency, on the contrast
> system emulation can be used to verify linux kernel. Is there any requirement
> for system emulation of new architecture?

I think we'd need some way of automatic regression testing for new targets. 
If your board has a serial UART that is easy to use, then please add a test 
in tests/qtest/boot-serial-test.c. And if there are any public Linux kernel 
binaries for (reliable) download anywhere, please add a test in 
tests/acceptance/, see for example the various machine_*.py files or 
boot_linux_console.py there.

 HTH,
  Thomas