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Commit 03ba32ca authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Gleb Natapov
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VMX: x86: handle host TSC calibration failure 

If the host TSC calibration fails, tsc_khz is zero (see tsc_init.c).
Handle such case properly in KVM (instead of dividing by zero).

https://bugzilla.redhat.com/show_bug.cgi?id=859282



Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
parent 0fa24ce3

arch/x86/kvm/x86.c

+18 −11
Original line number Diff line number Diff line
@@ -1079,6 +1079,10 @@ static void kvm_set_tsc_khz(struct kvm_vcpu *vcpu, u32 this_tsc_khz) 
	u32 thresh_lo, thresh_hi;

	int use_scaling = 0;



	/* tsc_khz can be zero if TSC calibration fails */

	if (this_tsc_khz == 0)

		return;



	/* Compute a scale to convert nanoseconds in TSC cycles */

	kvm_get_time_scale(this_tsc_khz, NSEC_PER_SEC / 1000,

			   &vcpu->arch.virtual_tsc_shift,
@@ -1156,6 +1160,7 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr) 
	ns = get_kernel_ns();

	elapsed = ns - kvm->arch.last_tsc_nsec;



	if (vcpu->arch.virtual_tsc_khz) {

		/* n.b - signed multiplication and division required */

		usdiff = data - kvm->arch.last_tsc_write;

#ifdef CONFIG_X86_64
@@ -1170,6 +1175,8 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr) 
		usdiff -= elapsed;

		if (usdiff < 0)

			usdiff = -usdiff;

	} else

		usdiff = USEC_PER_SEC; /* disable TSC match window below */



	/*

	 * Special case: TSC write with a small delta (1 second) of virtual