On Mon, Mar 2, 2020 at 9:09 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > On 02/03/20 18:01, Jim Mattson wrote: > >> And in fact, it's not used anywhere. So it should be > >> deprecated. > > I don't know how you can make the assertion that this ioctl is not > > used anywhere. For instance, I see a use of it in Google's code base. > > Right, it does not seem to be used anywhere according to e.g. Debian > code search but of course it can have users. > > What are you using it for? It's true that cpuid->nent is never written > back to userspace, so the ioctl is basically unusable unless you already > know how many entries are written. Or unless you fill the CPUID entries > with garbage before calling it, I guess; is that what you are doing? One could use GET_CPUID2 after SET_CPUID2, to see what changes kvm made to the requested guest CPUID information without telling you.
