Re: [PATCH v4 46/55] qapi: add query-targets

["Daniel P. Berrangé" <berrange@redhat.com>]

On Mon, Sep 28, 2026 at 06:51:41PM +0800, Yonggang Luo wrote:
> On Mon, Sep 28, 2026 at 6:39 PM Philippe Mathieu-Daudé <
> philmd@oss.qualcomm.com> wrote:
> >
> > On 28/9/26 12:13, Daniel P. Berrangé wrote:
> > > On Sat, Sep 26, 2026 at 03:00:45PM +0800, Yonggang Luo wrote:
> > >> query-targets lists each linked target, including none, with its
> > >> arch, endianness, and the machines that target accepts.
> > >>
> > >> Signed-off-by: Yonggang Luo <luoyonggang@gmail.com>
> > >> ---
> > >>   hw/core/machine-qmp-cmds.c | 30 ++++++++++++++++++++++++++++++
> > >>   qapi/machine.json          | 35 +++++++++++++++++++++++++++++++++++
> > >>   2 files changed, 65 insertions(+)
> > >
> > >
> > >> diff --git a/qapi/machine.json b/qapi/machine.json
> > >> index 6aaa2af709a..d8cdea6203e 100644
> > >> --- a/qapi/machine.json
> > >> +++ b/qapi/machine.json
> > >> @@ -307,6 +307,41 @@
> > >>   ##
> > >>   { 'command': 'query-target', 'returns': 'QemuTargetInfo' }
> > >>
> > >> +##
> > >> +# @TargetMachines:
> > >> +#
> > >> +# One registered system target and the machines that can run on it.
> > >> +#
> > >> +# @arch: the target architecture
> > >> +#
> > >> +# @endianness: the target endianness
> > >> +#
> > >> +# @machines: machine type names, not aliases
> > >> +#
> > >> +# Since: 11.2
> > >> +##
> > >> +{ 'struct': 'TargetMachines',
> > >> +  'data': { 'arch': 'SysEmuTarget',
> > >> +            'endianness': 'EndianMode',
> > >> +            'machines': ['str'] } }
> > >
> > > We already have  'QemuTargetInfo' struct which is used
> > > with 'query-target', that should also be used with the
> > > new 'query-targets' command.
> > >
> > > We need to add the 'endianness' field to QemuTargetInfo.
> >
> > Why do we want to expose endianness, and what endianness to
> > expose? Endianness is a runtime bit state of CPUs. Sometime
> > this bit is hardwired but that is an implementation detail.
> 
> For some targets it's, but for some targets it's not. for example
> 
> mips-softmmu.mak
> mipsel-softmmu.mak
> mips64el-softmmu.mak
> mips64-softmmu.mak
> 
> 
> mips64el-softmmu.mak
> mips64-softmmu.mak
> only differ the endianless

"EndianMode" is a tri-state including 'unspecified' as a value,
so we can cope with both scenarios - the targets where endianness
is runtime switchable in the CPU can use 'unspecified' as the
EndianMode. That behaviour should be documented in the QAPI
docs for QemuTargetInfo

With regards,
Daniel
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