On Thu, Sep 22, 2022 at 10:53 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > On Thu, Sep 22, 2022, Jim Mattson wrote: > > Why do we need a new 'scattered' leaf? We are only using two bits in > > the first one, right? And now we're only going to use one bit in the > > second one? > > > > I thought the point of the 'scattered' leaves was to collect a bunch > > of feature bits from different CPUID leaves in a single feature word. > > > > Allocating a new feature word for one or two bits seems extravagant. > > Ah, these leafs aren't scattered from KVM's perspective. > > The scattered terminology comes from the kernel side, where the KVM-only leafs > _may_ be used to deal with features that are scattered by the kernel. But there > is no requirement that KVM-only leafs _must_ be scattered by the kernel, e.g. we > can and should use this for leafs that KVM wants to expose to the guest, but are > completely ignored by the kernel. Intel's PSFD feature flag is a good example. > > A better shortlog would be: > > KVM: x86: Add a KVM-only leaf for CPUID_8000_0007_EDX Thanks. The 'scattered' terminology seems more confusing than enlightening.
