Intel does not have guest/host-only bit in perf counters like AMD
does.  To support GO/HO bits KVM needs to switch EVENTSELn values
(or PERF_GLOBAL_CTRL if available) at a guest entry. If a counter is
configured to count only in a guest mode it stays disabled in a host,
but VMX is configured to switch it to enabled value during guest entry.

This patch adds GO/HO tracking to Intel perf code and provides interface
for KVM to get a list of MSRs that need to be switched on a guest entry.

Only cpus with architectural PMU (v1 or later) are supported with this
patch.  To my knowledge there is not p6 models with VMX but without
architectural PMU and p4 with VMX are rare and the interface is general
enough to support them if need arise.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1317816084-18026-7-git-send-email-gleb@redhat.comSigned-off-by: Ingo Molnar <mingo@elte.hu>