Re: [Qemu-devel] [PATCH] qapi: add 'query-target' command to return target arch/bit size

[Anthony Liguori <aliguori@us.ibm.com>]

"Daniel P. Berrange" <berrange@redhat.com> writes:

> On Tue, Aug 21, 2012 at 09:53:55AM -0300, Luiz Capitulino wrote:
>> On Tue, 21 Aug 2012 11:07:50 +0100
>> "Daniel P. Berrange" <berrange@redhat.com> wrote:
>> 
>> > On Mon, Aug 20, 2012 at 04:02:39PM -0300, Luiz Capitulino wrote:
>> > > On Mon, 20 Aug 2012 15:31:38 +0100
>> > > "Daniel P. Berrange" <berrange@redhat.com> wrote:
>> > > 
>> > > > From: "Daniel P. Berrange" <berrange@redhat.com>
>> > > > 
>> > > > Add a 'query-target' QAPI command to allow management applications
>> > > > to determine what target architecture a QEMU binary is emulating
>> > > > without having to parse the binary name or -help output
>> > > > 
>> > > >   $ qmp-shell -p /tmp/qemu
>> > > >   (QEMU) query-target
>> > > >   {   u'return': {   u'arch': u'x86_64', u'bits': 64}}
>> > > > 
>> > > > Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
>> > > > ---
>> > > >  arch_init.c      | 11 +++++++++++
>> > > >  qapi-schema.json | 25 +++++++++++++++++++++++++
>> > > >  qmp-commands.hx  |  5 +++++
>> > > >  3 files changed, 41 insertions(+)
>> > > > 
>> > > > diff --git a/arch_init.c b/arch_init.c
>> > > > index 9b46bfc..095672d 100644
>> > > > --- a/arch_init.c
>> > > > +++ b/arch_init.c
>> > > > @@ -1080,3 +1080,14 @@ int xen_available(void)
>> > > >      return 0;
>> > > >  #endif
>> > > >  }
>> > > > +
>> > > > +
>> > > > +TargetInfo *qmp_query_target(Error **errp)
>> > > > +{
>> > > > +    TargetInfo *info = g_malloc0(sizeof(*info));
>> > > > +
>> > > > +    info->arch = g_strdup(TARGET_ARCH);
>> > > > +    info->bits = TARGET_PHYS_ADDR_BITS;
>> > > > +
>> > > > +    return info;
>> > > > +}
>> > > > diff --git a/qapi-schema.json b/qapi-schema.json
>> > > > index 3d2b2d1..f0e3fe0 100644
>> > > > --- a/qapi-schema.json
>> > > > +++ b/qapi-schema.json
>> > > > @@ -2454,3 +2454,28 @@
>> > > >  #
>> > > >  ##
>> > > >  { 'command': 'query-fdsets', 'returns': ['FdsetInfo'] }
>> > > > +
>> > > > +##
>> > > > +# @TargetInfo:
>> > > > +#
>> > > > +# Information describing the QEMU target.
>> > > > +#
>> > > > +# @arch: the name of the target architecture (eg "x86_64", "i686", etc)
>> > > 
>> > > Should be an enum, otherwise looks good.
>> > 
>> > Really ? It feels a little bit odd to make this an enum IMHO.
>> 
>> I don't think it's odd. We should avoid using free-form strings when
>> the set of possible values a command returns is limited and known.
>> 
>> The only small issue I see though, is that TARGET_ARCH is defined in
>> configure, so you'll have to add something like CONFIG_TARGET_ENUM there too
>
> Well the (slightly inefficient) way is to just iterate over the enum
> strings until you find the matching index. Not a good idea for large
> enums, but I figure it'd be acceptable for the small number of arches.

We can create a new CONFIG_ #define that gets set directly to the
enumerator value.   No need for string comparison.

Regards,

Anthony Liguori

>
> Daniel
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