Re: [PATCH 0/7] semihosting: proper QEMU exit on semihosted exit syscall

[Luc Michel <lmichel@kalray.eu>]

On 08:59 Mon 20 Jun     , Richard Henderson wrote:
> On 6/20/22 07:24, Luc Michel wrote:
> > Hi,
> > 
> > This series implements a clean way for semihosted exit syscalls to
> > terminate QEMU with a given return code.
> > 
> > Until now, exit syscalls implementations consisted in calling exit()
> > with the wanted return code. The problem with this approach is that
> > other CPUs are not properly stopped, leading to possible crashes in
> > MTTCG mode, especially when at_exit callbacks have been registered. This
> > can be the case e.g., when plugins are in use. Plugins can register
> > at_exit callbacks. Those will be called on the CPU thread the exit
> > syscall is comming from, while other CPUs can continue to run and thus
> > call other plugin callbacks.
> > 
> > The semihosting_exit_request function provides a mean to cleanly
> > terminate QEMU. It introduces an new exit reason
> > (SHUTDOWN_CAUSE_GUEST_SEMI_EXIT) used in this case. The CPU is stopped
> > and returns to the main CPU loop so that no more instruction get
> > executed (the semihosting_exit_request is declared G_NORETURN).
> > 
> > All targets are converted to use this new function.
> 
> Did you test a complete build?  At a glance I would guess that
> arm-linux-user will no longer link because qemu_set/get_exit_status is
> missing.

You are right I forgot to test build *-linux-user. There is a
compilation issue because I forgot "static inline" on the
semihosting_exit_request function on the CONFIG_USER_ONLY side. I'll fix
that in v2.

qemu_set/get_exit_status is fine though as it is only called from
softmmu-only code (and declared in sysemu/sysemu.h).

thanks,
Luc

> 
> 
> r~
> 
> > 
> > Thanks,
> > Luc
> > 
> > Luc Michel (7):
> >    softmmu: add qemu_[set|get]_exit_status functions
> >    semihosting: add the semihosting_exit_request function
> >    semihosting/arm-compat-semi: use semihosting_exit_request
> >    target/m68k: use semihosting_exit_request on semihosted exit syscall
> >    target/mips: use semihosting_exit_request on semihosted exit syscall
> >    target/nios2: use semihosting_exit_request on semihosted exit syscall
> >    target/xtensa: use semihosting_exit_request on semihosted exit syscall
> > 
> >   qapi/run-state.json                |  4 +++-
> >   include/semihosting/semihost.h     |  4 ++++
> >   include/sysemu/sysemu.h            |  2 ++
> >   semihosting/arm-compat-semi.c      |  3 +--
> >   semihosting/config.c               | 17 +++++++++++++++++
> >   softmmu/main.c                     |  2 +-
> >   softmmu/runstate.c                 | 11 +++++++++++
> >   target/m68k/m68k-semi.c            |  4 ++--
> >   target/mips/tcg/sysemu/mips-semi.c |  2 +-
> >   target/nios2/nios2-semi.c          |  4 ++--
> >   target/xtensa/xtensa-semi.c        |  2 +-
> >   11 files changed, 45 insertions(+), 10 deletions(-)
> > 
> 
> 
> 
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> 

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