On 28.02.2023 08:09, Xenia Ragiadakou wrote: > > On 2/27/23 14:17, Jan Beulich wrote: >> On 27.02.2023 13:06, Andrew Cooper wrote: >>> On 27/02/2023 11:33 am, Jan Beulich wrote: >>>> On 27.02.2023 12:15, Andrew Cooper wrote: >>>>> On 27/02/2023 10:46 am, Jan Beulich wrote: >>>>>> On 24.02.2023 22:33, Andrew Cooper wrote: >>>>>>> But I think we want to change tact slightly at this point, so I'm not >>>>>>> going to do any further tweaking on commit. >>>>>>> >>>>>>> Next, I think we want to rename asm/hvm/svm/svm.h to asm/hvm/svm.h, >>>>>>> updating the non-SVM include paths as we go. Probably best to >>>>>>> chain-include the other svm/hvm/svm/*.h headers temporarily, so we've >>>>>>> only got one tree-wide cleanup of the external include paths. >>>>>>> >>>>>>> Quick tangent - I will be making all of that cpu_has_svm_* >>>>>>> infrastructure disappear by moving it into the normal CPUID handling, >>>>>>> but I've not had sufficient time to finish that yet. >>>>>>> >>>>>>> Next, hvm/svm/nestedsvm.h can merge straight into hvm/svm.h, and >>>>>>> disappear (after my decoupling patch has gone in). >>>>>> Why would you want to fold hvm/svm/nestedsvm.h into hvm/svm/svm.h? >>>>>> The latter doesn't use anything from the former, does it? >>>>> It's about what else uses them. >>>>> >>>>> hvm_vcpu needs both svm_vcpu and nestedsvm, so both headers are always >>>>> included in tandem. >>>> Well, yes, that's how things are today. But can you explain to me why >>>> hvm_vcpu has to know nestedsvm's layout? >>> >>> Because it's part of the same single memory allocation. >> >> Which keeps growing, and sooner or later we'll need to find something >> again to split off, so we won't exceed a page in size. The nested >> structures would, to me, look to be prime candidates for such. >> >>>> If the field was a pointer, >>>> a forward decl of that struct would suffice, and any entity in the >>>> rest of Xen not caring about struct nestedsvm would no longer see it >>>> (and hence also no longer be re-built if a change is made there). >>> >>> Yes, you could hide it as a pointer. The cost of doing so is an >>> unnecessary extra memory allocation, and extra pointer handling on >>> create/destroy, not to mention extra pointer chasing in memory during use. >>> >>>>> nestedsvm is literally just one struct now, and no subsystem ought to >>>>> have multiple headers when one will do. >>>> When one will do, yes. Removing build dependencies is a good reason >>>> to have separate headers, though. >>> >>> Its not the only only option, and an #ifdef CONFIG_NESTED_VIRT inside >>> the struct would be an equally acceptable way of doing this which >>> wouldn't involve making an extra memory allocation. >> >> That would make it a build-time decision, but then on NESTED_VIRT=y >> hypervisors there might still be guests not meaning to use that >> functionality, and for quite some time that may actually be a majority. >> >>> Everything you've posed here is way out of scope for Xenia's series. >> >> There was never an intention to extend the scope of the work she's doing. >> Instead I was trying to limit the scope by suggesting to avoid a piece >> of rework which later may want undoing. > > Can I suggest to leave hvm/svm/svm.h and hvm/svm/nestedsvm.h separate > for now?
As per before - that's my preference. It'll be Andrew who you would need to convince, as he did suggest the folding. Jan
