KVM: x86: Add support for AMD Core Perf Extension in guest

Add support for AMD Core Performance counters in the guest. The base
event select and counter MSRs are changed. In addition, with the core
extension, there are 2 extra counters available for performance
measurements for a total of 6.

With the new MSRs, the logic to map them to the gp_counters[] is changed.
New functions are added to check the validity of the get/set MSRs.

If the guest has the X86_FEATURE_PERFCTR_CORE cpuid flag set, the number
of counters available to the vcpu is set to 6. It the flag is not set
then it is 4.

Signed-off-by: Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>
[Squashed "Expose AMD Core Perf Extension flag to guests" - Radim.]
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/kvm/x86.c

@@ -2579,6 +2579,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_AMD64_DC_CFG:
 		msr_info->data = 0;
 		break;
+	case MSR_F15H_PERF_CTL0 ... MSR_F15H_PERF_CTR5:
 	case MSR_K7_EVNTSEL0 ... MSR_K7_EVNTSEL3:
 	case MSR_K7_PERFCTR0 ... MSR_K7_PERFCTR3:
 	case MSR_P6_PERFCTR0 ... MSR_P6_PERFCTR1: