Re: [RFC][PATCH 0/2] x86: Add "virt flags"

Ingo Molnar
2008-09-08T14:10:09Z

* Sheng Yang <sheng.yang@intel.com> wrote:

> Hi, Ingo
>
> (sorry for former noises, I mistake the address... Report to lkml)
> I've sent this patchset before, but got no comments from upstream at
> that time. So I'd like to resend this.
>
> The virt flags is used for the important hardware virtualization
> features, like EPT of incoming Nehalem. Because the feature
> availability are read from MSRs, and I think virtualization features
> should not at the same level as "vmx", so I added a new flags catagory
> here.
>
> But I still have concern, for this may broke some not that reliable
> userspace programs. So Avi suggested that we can add more fields to
> flags rather than a new catagory. What's your opinion? We indeed need
> a generic user visible way to tell the HW virtualization features.

hm, i think extending the already existing flags category sounds like a
better solution than the separate virtual CPU flags line in
/proc/cpuinfo. We already have self-invented flag entries (such as
X86_FEATURE_NOPL), and adding more for virtualization would be quite
natural to do, as long as it's reasonably close to the meaning of a 'CPU
feature'.

Peter, what would be your preference?

Ingo