Zachary Amsden wrote: > H. Peter Anvin wrote: >> >> This code is almost entirely identical to the setgpr_wrapper in the >> patch (except for the fact that setgpr_wrapper sets and captures *ALL* >> the GPRs), and it seems rather pointless to use another wrapper. It >> takes a pointer to an entrypoint (default to "cpuid; ret" in the CPUID >> case), so it should do what you need. > > void (*cpuid)(unsigned int *eax, unsigned int *ebx, ...) > > Not quite. The paravirt_ops CPUID function is a C function which takes > pointers to each GPR as arguments, and returns the values through those > pointers. This doesn't allow for an entrypoint compatible with > setgpr_wrapper, which expects the same output in both the cpuid; ret > case and the paravirt-ops case. > > One could argue that the paravirt-ops CPUID should in fact emulate the > native instruction semantics, which would make it a non-C function. > However, until that bridge is crossed, we would need another wrapper > after setgpr to convert the paravirt-ops CPUID back into the same format > as native so that setgpr_wrapper can properly store the output fields > into the common i386/x86_64 structure. What definitely should be done > is hide this secondary wrapper in the paravirt-ops code so that your > setgpr wrapper doesn't have to deal with weird issues like this because > of paravirt-ops changes. I guess what I was trying to say was that we'd use setgpr_wrapper in the case where you have an entrypoint with native (non-C) semantics; in the other case we'd use an alternative to setgpr_wrapper. Either way, it sounds like we're talking about implementing paravirtualization *after* CPU selection, i.e. we use IPI to get the thing running on the proper CPU before invoking the paravirtualization function? -hpa _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
