On Wed, Dec 12, 2012 at 03:47:49PM +0100, Andreas Färber wrote: > Am 12.12.2012 13:45, schrieb Eduardo Habkost: > > On Mon, Dec 10, 2012 at 11:59:32PM +0100, Andreas Färber wrote: > >> ehabkost: "When adding the Haswell CPU model, I intended to make it > >> a superset of the features present on the SandyBridge model" > >> > >> Inherit from SandyBridge to keep only the delta for Haswell. > > > > Most CPUs have a superset of the features of their predecessors. Are you > > simply using SandyBridge->Haswell as an example, or you think their > > relationship is special somehow? > > > > I believe we don't want to make externally-visible class inheritance, > > but probably just reuse constans or init functions internally. A Haswell > > CPU is not a type of SandyBridge CPU, it just happens to contain a > > superset of the features present in SandyBridge. > > > > I mean: Haswell also has a superset of features of 486, but we don't > > want to make the hierarchy look like the following, do we? > > I don't see why we would want to use a #define-based inheritence as > suggested for the PPRO when we have QOM. QOM inheritence reduces lines > of code significantly compared to just taking the values from elsewhere.
The reuse doesn't need to be #define-based (although maybe a #define-based approach would work too), it could be function-call-based. > > For the Haswell you said what I quoted, for the other models I said I > need your or someone's help to verify whether a hierarchy such as below > is semantically right or just a coincidence. I was at least considering > an abstract intel-/amd-*-cpu to avoid repeating the three value > assignments over and over. Creating X86IntelCPU and X86AMDCPU classes make sense to me, because Haswell is a kind of Intel CPu. Making Haswell a subclass of 486 (like below) wouldn't. > > At this time I believe the parents of a type are not (yet) exposed via > QMP, just the "type" string property. Even if they are not exposed externally, it's a confusing usage of inheritance for me. I mean: a Haswell CPU is not a type of 486 CPU, it's simply a different kind of CPU that happens to have a superset of the 486 features. > > Andreas > > > - X86CPU > > -> X86IntelCPU > > -> 486 > > -> pentium > > -> pentium2 > > -> pentium3 > > -> Conroe > > -> Penryn > > -> Nehalem > > -> Westmere > > -> SandyBridge > > -> Haswell > > -- > SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany > GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg -- Eduardo
