On 27/07/2015 17:56, Andy Lutomirski wrote: > On Mon, Jul 27, 2015 at 6:59 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: >> >> >> On 24/07/2015 19:33, Andy Lutomirski wrote: >>> PARAVIRT adds a fair amount of bloat and, AFAICT, KVM_GUEST doesn't >>> really need any of it. Would it make sense to drop the dependency? >> >> I think the main reason for PARAVIRT is that pv kernels have by default >> >> .read_msr = native_read_msr_safe, >> .write_msr = native_write_msr_safe, >> >> Unfortunately Intel adds a bunch of performance measurement features >> saying that "they work with this cpuid family/model/stepping" and at the >> same time attach them to some non-architectural MSRs that, in principle >> could be reused for something else years down the road. This is not a >> huge problem for Windows, where only tools such as vTune use these MSRs, >> but it is a problem for Linux. >> >> The alternative is ignore_msrs, but that's a very big hammer too. > > I think I'm missing something. Does KVM_GUEST hook read_msr and > write_msr? I don't see it. PARAVIRT does, and it's the main reason why you'd want PARAVIRT for a KVM guest. Paolo > Xen certainly needs those hooks, but I don't see why KVM would. > > --Andy > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
