On 3/6/23 22:44, Borislav Petkov wrote:
I thought that the consensus was that adding unused-by-the-kernel flags to
cpufeatures.h is ok so long as the feature is hidden from /proc/cpuinfo and the
kernel already dedicates a word to the CPUID leaf?
I guess we should finally write it down in Documentation/x86/cpuinfo.rst
And in case there's no dedicated word, it should be resorted to KVM-only
feature flags.
In any case, I'd like for baremetal CPUID stuff to be decoupled from
KVM's machinery as far as possible as both have different goals wrt
feature flags.
It's very rare that KVM can provide a CPUID feature if the kernel has
masked it, so if the kernel needs to know about a feature word than KVM
most likely needs to know what kind of massaging the kernel has done.
Paolo
