diff options
Diffstat (limited to 'arch/x86/kvm/x86.c')
| -rw-r--r-- | arch/x86/kvm/x86.c | 40 |
1 files changed, 39 insertions, 1 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index ef5b9d66cd71..1473e64cb744 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1329,6 +1329,33 @@ static void update_ia32_tsc_adjust_msr(struct kvm_vcpu *vcpu, s64 offset) vcpu->arch.ia32_tsc_adjust_msr += offset - curr_offset; } +/* + * Multiply tsc by a fixed point number represented by ratio. + * + * The most significant 64-N bits (mult) of ratio represent the + * integral part of the fixed point number; the remaining N bits + * (frac) represent the fractional part, ie. ratio represents a fixed + * point number (mult + frac * 2^(-N)). + * + * N equals to kvm_tsc_scaling_ratio_frac_bits. + */ +static inline u64 __scale_tsc(u64 ratio, u64 tsc) +{ + return mul_u64_u64_shr(tsc, ratio, kvm_tsc_scaling_ratio_frac_bits); +} + +u64 kvm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc) +{ + u64 _tsc = tsc; + u64 ratio = vcpu->arch.tsc_scaling_ratio; + + if (ratio != kvm_default_tsc_scaling_ratio) + _tsc = __scale_tsc(ratio, tsc); + + return _tsc; +} +EXPORT_SYMBOL_GPL(kvm_scale_tsc); + void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr) { struct kvm *kvm = vcpu->kvm; @@ -7371,8 +7398,19 @@ int kvm_arch_hardware_setup(void) if (r != 0) return r; - if (kvm_has_tsc_control) + if (kvm_has_tsc_control) { + /* + * Make sure the user can only configure tsc_khz values that + * fit into a signed integer. + * A min value is not calculated needed because it will always + * be 1 on all machines. + */ + u64 max = min(0x7fffffffULL, + __scale_tsc(kvm_max_tsc_scaling_ratio, tsc_khz)); + kvm_max_guest_tsc_khz = max; + kvm_default_tsc_scaling_ratio = 1ULL << kvm_tsc_scaling_ratio_frac_bits; + } kvm_init_msr_list(); return 0; |