KVM: x86: Collect information for setting TSC scaling ratio

The number of bits of the fractional part of the 64-bit TSC scaling
ratio in VMX and SVM is different. This patch makes the architecture
code to collect the number of fractional bits and other related
information into variables that can be accessed in the common code.
Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -988,6 +988,10 @@ u64 vcpu_tsc_khz(struct kvm_vcpu *vcpu);
 extern bool kvm_has_tsc_control;
 /* maximum supported tsc_khz for guests */
 extern u32  kvm_max_guest_tsc_khz;
+/* number of bits of the fractional part of the TSC scaling ratio */
+extern u8   kvm_tsc_scaling_ratio_frac_bits;
+/* maximum allowed value of TSC scaling ratio */
+extern u64  kvm_max_tsc_scaling_ratio;
 
 enum emulation_result {
 	EMULATE_DONE,         /* no further processing */

arch/x86/kvm/svm.c

@@ -908,6 +908,9 @@ static __init int svm_hardware_setup(void)
 		max = min(0x7fffffffULL, __scale_tsc(tsc_khz, TSC_RATIO_MAX));
 
 		kvm_max_guest_tsc_khz = max;
+
+		kvm_max_tsc_scaling_ratio = TSC_RATIO_MAX;
+		kvm_tsc_scaling_ratio_frac_bits = 32;
 	}
 
 	if (nested) {

arch/x86/kvm/x86.c

@@ -109,6 +109,10 @@ bool __read_mostly kvm_has_tsc_control;
 EXPORT_SYMBOL_GPL(kvm_has_tsc_control);
 u32  __read_mostly kvm_max_guest_tsc_khz;
 EXPORT_SYMBOL_GPL(kvm_max_guest_tsc_khz);
+u8   __read_mostly kvm_tsc_scaling_ratio_frac_bits;
+EXPORT_SYMBOL_GPL(kvm_tsc_scaling_ratio_frac_bits);
+u64  __read_mostly kvm_max_tsc_scaling_ratio;
+EXPORT_SYMBOL_GPL(kvm_max_tsc_scaling_ratio);
 
 /* tsc tolerance in parts per million - default to 1/2 of the NTP threshold */
 static u32 __read_mostly tsc_tolerance_ppm = 250;