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authorMarcelo Tosatti <mtosatti@redhat.com>2013-03-11 23:10:24 -0300
committerGleb Natapov <gleb@redhat.com>2013-03-12 13:18:00 +0200
commit03ba32cae66e3798d697e582633af2c7dd6907e5 (patch)
treef57ea6a992f4032a83af79f20a5dd63818bf0b99 /arch/x86/kvm/x86.c
parent0fa24ce3f57144e390a1566774c23434975a52a9 (diff)
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: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
Diffstat (limited to 'arch/x86/kvm/x86.c')
-rw-r--r--arch/x86/kvm/x86.c29
1 files changed, 18 insertions, 11 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 35b491229c3a..b67985af1753 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -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