On Tue, 26 Feb 2013 14:21:22 -0300 Eduardo Habkost <ehabk...@redhat.com> wrote:
> On Tue, Feb 26, 2013 at 06:10:25PM +0100, Igor Mammedov wrote: > > On Tue, 26 Feb 2013 14:06:05 -0300 > > Eduardo Habkost <ehabk...@redhat.com> wrote: > > > > > On Tue, Feb 26, 2013 at 05:39:02PM +0100, Igor Mammedov wrote: > > > [...] > > > > > > > > > * I don't expect hv-* to appear on a machine-type compat_props > > > > > > > > > array in the near feature. > > > > > > > > > * I don't expect people to need to set per-CPU hv-* properties > > > > > > > > > on device_add for CPU hotplug. > > > > > > > > > > > > > > > > > > So we could keep them as special cases on parse_featurestr(), > > > > > > > > > and convert them to per-CPU properties only after we have the > > > > > > > > > subclasses and CPU hotplug working. > > > > > > > > it won't be a consistent interface, where user who has > > > > > > > > "-cpu XXX,+foo1,+hv_spinlocks,+foo2" on cmd-line > > > > > > > > would have to use "device_add XXX,foo1=true,foo2=true" manually > > > > > > > > excluding options from device_add, i.e. it propagates special > > > > > > > > casing to users as well. And when hv_ are moved to per-CPU > > > > > > > > fields, it might break users since they will still exclude some > > > > > > > > options. > > > > > > > > > > > > > > Won't -cpu/parse_featurestr() simply set global properties? In > > > > > > > this > > > > > > > case, the common case would be to call "device_add XXX" with no > > > > > > > extra options at all, so there's no option to be excluded and no > > > > > > > special case to care about. > > > > > > That is if global properties will made to 1.5 which I highly doubt > > > > > > taking in account how fast patches are reviewed and accepted. > > > > > > Otherwise release would be broken. > > > > > > > > > > IMO it _has_ to make 1.5 and is a requirement to make device_add > > > > > usable > > > > > for CPU hotplug. Otherwise we would have to change the behavior of > > > > > -cpu > > > > > + device_add in an incompatible way. > > > > if all -cpu features are converted to static properties, we do not have > > > > to > > > > have global properties working. In absence of 'global properties', user > > > > will have to use the same properties at device_add that was specified at > > > > -cpu. And introduction of global properties won't regress it, it will > > > > just allow to use device_add without features specified on -cpu > > > > > > Strictly, we do not have to, but changing -cpu to set global properties > > > only later would change the behavior of "-cpu XXX,foo=1,bar=2" followed > > > by "device_add XXX" in an incompatible way. So if our long-term plan is > > Could you explain how ^^^ it will be incompatible, pls? > > Suppose that "foo" defaults to 0, and we run: "-cpu XXX,foo=1", followed > by "device_add XXX". > > Without globals/defaults set by -cpu, the above will create a new CPU > with foo=0. > > With globals/defaults set by -cpu, the above will create a new CPU with > foo=1. > > If I recall correctly, we agreed that the latter is the behavior we > wanted (because it is simpler for users, matches the fact that "-cpu" > already affects multiple CPU devices [it already affects all the CPUs > created on startup], and is the most common use-case [creating CPUs that > look basically the same]). Yes, that is the goal. I wouldn't say incompatible if user will start QEMU with "-cpu XXX,foo=1" and then use "device_add XXX,foo=1". That's a strict minimum that would work for hot-plug. Plain "device_add XXX" is an invalid in this case since it won't produce the same CPU. So later on top of "-cpu XXX,foo=1" + "device_add XXX,foo=1" we add up conversion of -cpu to global properties it shouldn't break anything, only add new option to create the same CPU usin "device_add XXX", users will still be able to use "device_add XXX,foo=1" if desired. I hope that -cpu => global properties will make it in 1.5, but it is not must have show-stopper for hot-plug if it misses it. > > -- > Eduardo > -- Regards, Igor
