Hi Markus and Daniel, I have the questions about the -object per cache implementation:
On Wed, Jul 24, 2024 at 02:39:29PM +0200, Markus Armbruster wrote: > Date: Wed, 24 Jul 2024 14:39:29 +0200 > From: Markus Armbruster <arm...@redhat.com> > Subject: Re: [PATCH 8/8] qemu-options: Add the description of smp-cache > object > > Zhao Liu <zhao1....@intel.com> writes: > > > Hi Markus, > > > > On Mon, Jul 22, 2024 at 03:37:43PM +0200, Markus Armbruster wrote: > >> Date: Mon, 22 Jul 2024 15:37:43 +0200 > >> From: Markus Armbruster <arm...@redhat.com> > >> Subject: Re: [PATCH 8/8] qemu-options: Add the description of smp-cache > >> object > >> > >> Zhao Liu <zhao1....@intel.com> writes: > >> > >> > Signed-off-by: Zhao Liu <zhao1....@intel.com> > >> > >> This patch is just documentation. The code got added in some previous > >> patch. Would it make sense to squash this patch into that previous > >> patch? > > > > OK, I'll merge them. > > > >> > --- > >> > Changes since RFC v2: > >> > * Rewrote the document of smp-cache object. > >> > > >> > Changes since RFC v1: > >> > * Use "*_cache=topo_level" as -smp example as the original "level" > >> > term for a cache has a totally different meaning. (Jonathan) > >> > --- > >> > qemu-options.hx | 58 +++++++++++++++++++++++++++++++++++++++++++++++++ > >> > 1 file changed, 58 insertions(+) > >> > > >> > diff --git a/qemu-options.hx b/qemu-options.hx > >> > index 8ca7f34ef0c8..4b84f4508a6e 100644 > >> > --- a/qemu-options.hx > >> > +++ b/qemu-options.hx > >> > @@ -159,6 +159,15 @@ SRST > >> > :: > >> > > >> > -machine > >> > cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.targets.1=cxl.1,cxl-fmw.0.size=128G,cxl-fmw.0.interleave-granularity=512 > >> > + > >> > + ``smp-cache='id'`` > >> > + Allows to configure cache property (now only the cache topology > >> > level). > >> > + > >> > + For example: > >> > + :: > >> > + > >> > + -object > >> > '{"qom-type":"smp-cache","id":"cache","caches":[{"name":"l1d","topo":"core"},{"name":"l1i","topo":"core"},{"name":"l2","topo":"module"},{"name":"l3","topo":"die"}]}' > >> > + -machine smp-cache=cache > >> > ERST > >> > > >> > DEF("M", HAS_ARG, QEMU_OPTION_M, > >> > @@ -5871,6 +5880,55 @@ SRST > >> > :: > >> > > >> > (qemu) qom-set /objects/iothread1 poll-max-ns 100000 > >> > + > >> > + ``-object > >> > '{"qom-type":"smp-cache","id":id,"caches":[{"name":cache_name,"topo":cache_topo}]}'`` > >> > + Create an smp-cache object that configures machine's cache > >> > + property. Currently, cache property only include cache topology > >> > + level. > >> > + > >> > + This option must be written in JSON format to support JSON list. > >> > >> Why? > > > > I'm not familiar with this, so I hope you could educate me if I'm wrong. > > > > All I know so far is for -object that defining a list can only be done in > > JSON format and not with a numeric index like a keyval based option, like: > > > > -object smp-cache,id=cache0,caches.0.name=l1i,caches.0.topo=core: Parameter > > 'caches' is missing > > > > the above doesn't work. > > > > Is there any other way to specify a list in command line? > > The command line is a big, sprawling mess :) > > -object supports either a JSON or a QemuOpts argument. *Not* keyval! > > Both QemuOpts and keyval parse something like KEY=VALUE,... Keyval > supports arrays and objects via dotted keys. QemuOpts doesn't natively > support arrays and objects, but its users can hack around that > limitation in various ways. -object doesn't. So you're right, it's > JSON or bust here. > > However, if we used one object per cache instead, we could get something > like > > -object smp-cache,name=l1d,... > -object smp-cache,name=l1u,... > -object smp-cache,name=l2,... > ... Current, I use -object to create a smp_cache object, and link it to MachineState by -machine,smp-cache=obj_id. Then for the objects per cache, how could I link them to machine? Is it possible that I create something static in smp_cache.c and expose all the cache information to machine through some interface? Additionally, I would like to consider for the long term heterogeneous cache, as asked before in [1], does the object per cache conflict with the cache device I'm considering? Considering cache device is further because I want to create CPU/cache topology via -device and build a topology tree. [1]: https://lore.kernel.org/qemu-devel/zl88dywle3scd...@intel.com/ I think this is becoming a nightmare I can't get around. Naming is difficult, and sorting out interface design I think is also a difficult task. If you feel that there is indeed a conflict, then I'm also willing to fall back to -smp again and do it based on keyval's list, as originally suggested by Daniel. Sorry for the repetition on thoughts/design, I hope that discussion with you I can make sense of the current and subsequent paths without getting out of hand! Best Regards, Zhao