On Monday 27 July 2009 17:08:42 Jan Kiszka wrote:

[ carrying this to LKML ]

Yang, Sheng wrote:

quoted

On Monday 27 July 2009 03:16:27 H. Peter Anvin wrote:

quoted

Jan Kiszka wrote:

quoted

Avi Kivity wrote:

quoted

On 07/24/2009 12:41 PM, Jan Kiszka wrote:

quoted

I vaguely recall that someone promised to add a feature reporting
facility for all those nice things, modern VM-extensions may or may
not support (something like or even an extension of /proc/cpuinfo).
What is the state of this plan? Would be specifically interesting for
Intel CPUs as there seem to be many of them out there with
restrictions for special use cases - like real-time.

Newer kernels do report some vmx features (like flexpriority) in
/proc/cpuinfo but not all.

Ah, nice. Then we just need this?

Fine with me.

Acked-by: H. Peter Anvin <hpa@zytor.com>

However, I guess the real question if we shouldn't export ALL VMX
features in a consistent way instead?

When I add feature reporting to cpuinfo, I just put highlight features
there, otherwise the VMX feature list would at least as long as CPU one.

That could become true. But the question is always what the highlights
are. Often this depends on the hypervisor as it may implement
workarounds for missing features differently (or not at all). So I'm
also for exposing feature information consistently.

(CC Andi and Ingo)

The highlight means the feature we would gain a lot, like FlexPriority, EPT, 
VPID. They can be vendor specific. And I am talking about hardware capability 
here, so what's hypervisor did for workaround is not in scope.

quoted

I have also suggested another field for virtualization feature for it,
but some concern again userspace tools raised.

For we got indeed quite a lot features, and would get more, would it
better to export the part of struct vmcs_config entries(that's
pin_based_exec_ctrl, cpu_based_exec_ctrl, and cpu_based_2nd_exec_ctrl)
through
sys/module/kvm_intel/? Put every feature to cpuinfo seems not that
necessary for such a big list.

I don't think this information should only come from KVM. Consider you
didn't build it into some kernel but still want to find out what your
system is able to provide.

Yes, agree.

What about adding some dedicated /proc entry for CPU virtualization
features, say /proc/hvminfo?

Well, compared to this, I may still prefer a new item in /proc/cpuinfo, for 
it's still CPU feature, like Andi did for power management(IIRC).

Any more preferred location?

-- 
regards
Yang, Sheng