On Mon, Mar 2, 2020 at 7:25 PM Jim Mattson <jmattson@xxxxxxxxxx> wrote: > > On Mon, Mar 2, 2020 at 11:57 AM Sean Christopherson > <sean.j.christopherson@xxxxxxxxx> wrote: > > > The bad behavior can be visually confirmed by dumping CPUID output in > > the guest when running Qemu with a stable TSC, as Qemu extends the limit > > of range 0x40000000 to 0x40000010 to advertise VMware's cpuid_freq, > > without defining zeroed entries for 0x40000002 - 0x4000000f. > > I think it could be reasonably argued that this is a userspace bug. > Clearly, when userspace explicitly supplies the results for a leaf, > those results override the default CPUID values for that leaf. But I > haven't seen it documented anywhere that leaves *not* explicitly > supplied by userspace will override the default CPUID values, just > because they happen to appear in some magic range. In fact, the more I think about it, the original change is correct, at least in this regard. Your "fix" introduces undocumented and unfathomable behavior.
