Il 29/08/2014 02:13, Andy Lutomirski ha scritto:

Hmm.  Then, assuming that someone manages to allocate a
cross-hypervisor MSR number for this, what am I supposed to do in the
KVM code?  Just make it available unconditionally?  I don't see why
that wouldn't work reliably, but it seems like an odd design.

The odd part of it is what Gleb mentioned.

Also, the one and only native feature flag I tested (rdtscp) actually
does work: RDTSCP seems to send #UD if QEMU is passed -cpu
host,-rdtscp.

True, and I'm not sure why.  There are a couple others.  I was thinking
more of things like SSE, AVX or DE (that affects the availability of a
bit in CR4).

Paolo