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Fix divide by zero on host TSC calibration failure (rhbz 859282)

This commit is contained in:
Josh Boyer 2013-03-14 07:45:49 -04:00
parent d07c9bf44a
commit 5d9a19407d
2 changed files with 67 additions and 0 deletions
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58
VMX-x86-handle-host-TSC-calibration-failure.patch Normal file
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@ -0,0 +1,58 @@
@@ -, +, @@
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>
--- a/arch/x86/kvm/x86.c
+++ a/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

9
kernel.spec
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@ -789,6 +789,9 @@ Patch24110: mac80211-Fix-crash-due-to-un-canceled-work-items.patch
Patch24111: cfg80211-mac80211-disconnect-on-suspend.patch
Patch24112: mac80211_fixes_for_ieee80211_do_stop_while_suspend_v3.8.patch
#rhbz 859282
Patch24113: VMX-x86-handle-host-TSC-calibration-failure.patch
#rhbz 920586
Patch25000: amd64_edac_fix_rank_count.patch
@ -1548,6 +1551,9 @@ ApplyPatch mac80211-Fix-crash-due-to-un-canceled-work-items.patch
ApplyPatch cfg80211-mac80211-disconnect-on-suspend.patch
ApplyPatch mac80211_fixes_for_ieee80211_do_stop_while_suspend_v3.8.patch
#rhbz 859282
ApplyPatch VMX-x86-handle-host-TSC-calibration-failure.patch
# END OF PATCH APPLICATIONS
%endif
@ -2404,6 +2410,9 @@ fi
# '-' | |
# '-'
%changelog
* Thu Mar 14 2013 Josh Boyer <jwboyer@redhat.com>
- Fix divide by zero on host TSC calibration failure (rhbz 859282)
* Thu Mar 14 2013 Mauro Carvalho Chehab <mchehab@redhat.com>
- fix i7300_edac twice-mem-size-report via EDAC API (rhbz 921500)