On 02/03/20 18:44, Jim Mattson wrote: > 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. Yeah, I think GET_CPUID2 with the same number of leaves that you have passed to SET_CPUID2 should work. Paolo
