On Tue, May 09, 2017 at 03:13:37PM +0100, Richard W.M. Jones wrote: > On Tue, May 09, 2017 at 07:05:51AM -0700, Richard Henderson wrote: > > On 05/09/2017 06:27 AM, Daniel P. Berrange wrote: > > >This enables report of a signature in CPUID for the TCG > > >interpretor. > > > > > >Changed in v4: > > > > > > - Report 0x40000001 in EAX for 0x40000000 index (Eduardo) > > > - Report all zeros for 0x40000001 index (Eduardo) > > > - Make code style consistent when checking limits (Eduardo) > > > > > >Changed in v3: > > > > > > - Simplify CPU limit code still further (Eduardo) > > > > > >Changed in v2: > > > > > > - Rewrite the way we bounds check / cap the CPUID index > > > to use a flat switch, instead of nested ifs (Eduardo) > > > - Add a 'tcg-cpuid' property to allow it to be hidden > > > (Eduardo) > > > - Hide the TCG signature for old machine types > > > - Force code to a no-op if tcg_enabled() is false (Eduardo) > > > > > > > > >NB, I did not introduce a general 'hypervisor-cpuid' property > > >to obsolete the existing 'kvm=off|on' -cpu property, since it > > >appears impossible to get the back compat semantics right, > > >as described in a previous reply. > > > > > >Daniel P. Berrange (2): > > > i386: rewrite way CPUID index is validated > > > i386: expose "TCGTCGTCGTCG" in the 0x40000000 CPUID leaf > > > > I probably should have commented earlier but... what's the point? > > > > If you want the guest os to actually do anything with this, what do > > you gain for advertising TCG over KVM? > > I can see this being useful from virt-what, since it would allow > vendors to diagnose problems being caused by TCG (since as Dan > mentions in the other reply and as you are already well acquainted > with, TCG and KVM don't present or emulate quite the same thing). > > That said, I don't think it's anything more than a nice to have.
We also have systemd-detect-virt, and the ConditionVirtualization option in systemd. -- Eduardo