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| author | Marcelo Tosatti <mtosatti@redhat.com> | 2013-03-11 23:10:24 -0300 |
|---|---|---|
| committer | Gleb Natapov <gleb@redhat.com> | 2013-03-12 13:18:00 +0200 |
| commit | 03ba32cae66e3798d697e582633af2c7dd6907e5 (patch) | |
| tree | f57ea6a992f4032a83af79f20a5dd63818bf0b99 /arch/x86/kvm/x86.c | |
| parent | 0fa24ce3f57144e390a1566774c23434975a52a9 (diff) | |
| download | lwn-03ba32cae66e3798d697e582633af2c7dd6907e5.tar.gz lwn-03ba32cae66e3798d697e582633af2c7dd6907e5.zip | |
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.c | 29 |
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 |