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VMX: x86: handle host TSC calibration failure

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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: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
This commit is contained in:
Marcelo Tosatti 2013-03-11 23:10:24 -03:00 committed by Gleb Natapov
parent 0fa24ce3f5
commit 03ba32cae6
1 changed files with 18 additions and 11 deletions
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29
arch/x86/kvm/x86.c
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@ -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,
@ -1156,20 +1160,23 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr)
ns = get_kernel_ns();
elapsed = ns - kvm->arch.last_tsc_nsec;
/* n.b - signed multiplication and division required */
usdiff = data - kvm->arch.last_tsc_write;
if (vcpu->arch.virtual_tsc_khz) {
/* n.b - signed multiplication and division required */
usdiff = data - kvm->arch.last_tsc_write;
#ifdef CONFIG_X86_64
usdiff = (usdiff * 1000) / vcpu->arch.virtual_tsc_khz;
usdiff = (usdiff * 1000) / vcpu->arch.virtual_tsc_khz;
#else
/* do_div() only does unsigned */
asm("idivl %2; xor %%edx, %%edx"
: "=A"(usdiff)
: "A"(usdiff * 1000), "rm"(vcpu->arch.virtual_tsc_khz));
/* do_div() only does unsigned */
asm("idivl %2; xor %%edx, %%edx"
: "=A"(usdiff)
: "A"(usdiff * 1000), "rm"(vcpu->arch.virtual_tsc_khz));
#endif
do_div(elapsed, 1000);
usdiff -= elapsed;
if (usdiff < 0)
usdiff = -usdiff;
do_div(elapsed, 1000);
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