On Thu, Sep 02, 2021 at 11:32:41AM -0300, Fabiano Rosas wrote: > David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> writes: > > > On Wed, Sep 01, 2021 at 02:33:52PM -0300, Fabiano Rosas wrote: > >> This series merges our three kvm modules kvm.ko, kvm-hv.ko and > >> kvm-pr.ko into one kvm.ko module. > > > > That doesn't sound like a good idea to me. People who aren't on BookS > > servers don't want - and can't use - kvm-hv. Almost nobody wants > > kvm-pr. It's also kind of inconsistent with x86, which has the > > separate AMD and Intel modules. > > But this is not altering the ability of having only kvm-hv or only > kvm-pr. I'm taking the Kconfig options that used to produce separate > modules and using them to select which code gets built into the one > kvm.ko module. > > Currently: > > CONFIG_KVM_BOOK3S_64=m <-- produces kvm.ko > CONFIG_KVM_BOOK3S_64_HV=m <-- produces kvm-hv.ko > CONFIG_KVM_BOOK3S_64_PR=m <-- produces kvm-pr.ko > > I'm making it so we now have one kvm.ko everywhere, but there is still: > > CONFIG_KVM_BOOK3S_64=m <-- produces kvm.ko > CONFIG_KVM_BOOK3S_HV_POSSIBLE=y <-- includes HV in kvm.ko > CONFIG_KVM_BOOK3S_PR_POSSIBLE=y <-- includes PR in kvm.ko > > In other words, if you are going to have at least two modules loaded at > all times (kvm + kvm-hv or kvm + kvm-pr), why not put all that into one > module? No one needs to build code they are not going to use, this is > not changing. Ah.. I see, you're removing the runtime switch from one to the other at the same time as having just a single one loaded, but leaving the ability to compile time switch. And compile time is arguably good enough for the cases I've described. Ok, I see your point. I still think it's conceptually not ideal, but the practical benefit is more important. Objection withdrawn. > About consistency with x86, this situation is not analogous because we > need to be able to load both modules at the same time, which means > kvm.ko needs to stick around when one module goes away in case we want > to load the other module. The KVM common code states that it expects to > have at most one implementation: > > /* > * kvm_arch_init makes sure there's at most one caller > * for architectures that support multiple implementations, > * like intel and amd on x86. > (...) > > which is not true in our case due to this requirement of having two > separate modules loading independently. > > (tangent) We are already quite different from other architectures since > we're not making use of kvm_arch_init and some other KVM hooks, such as > kvm_arch_check_processor_compat. So while other archs have their init > dispatched by kvm common code, our init and cleanup happens > independently in the ppc-specific modules, which obviously works but is > needlessly different and has subtleties in the ordering of operations > wrt. the kvm common code. (tangent) > -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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