When no platform bugs have been detected, no TSC warps have been detected, and the hardware guarantees to us TSC does not change rate or stop with P-state or C-state changes, we can consider it reliable.
Signed-off-by: Zachary Amsden <[email protected]> --- arch/x86/kvm/x86.c | 10 +++++++++- 1 files changed, 9 insertions(+), 1 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 86f182a..a7fa24e 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -55,6 +55,7 @@ #include <asm/mce.h> #include <asm/i387.h> #include <asm/xcr.h> +#include <asm/pvclock-abi.h> #define MAX_IO_MSRS 256 #define CR0_RESERVED_BITS \ @@ -900,6 +901,13 @@ static void kvm_get_time_scale(uint32_t scaled_khz, uint32_t base_khz, static DEFINE_PER_CPU(unsigned long, cpu_tsc_khz); unsigned long max_tsc_khz; +static inline int kvm_tsc_reliable(void) +{ + return (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && + boot_cpu_has(X86_FEATURE_NONSTOP_TSC) && + !check_tsc_unstable()); +} + static inline u64 nsec_to_cycles(struct kvm *kvm, u64 nsec) { return pvclock_scale_delta(nsec, kvm->arch.virtual_tsc_mult, @@ -1151,7 +1159,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) vcpu->hv_clock.tsc_timestamp = tsc_timestamp; vcpu->hv_clock.system_time = kernel_ns + v->kvm->arch.kvmclock_offset; vcpu->last_kernel_ns = kernel_ns; - vcpu->hv_clock.flags = 0; + vcpu->hv_clock.flags = kvm_tsc_reliable() ? PVCLOCK_TSC_STABLE_BIT : 0; /* * The interface expects us to write an even number signaling that the -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
