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 <[email protected]>
arch/x86/kvm/x86.c +18 -11
@@ -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
Quoted 8 lines · Marcelo Tosatti
If the host TSC calibration fails,
tsc_khzis zero (seetsc_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 <[email protected]>
Fixed small space/tab problem and applied. Thanks.
Quoted 40 lines
arch/x86/kvm/x86.c +12
-10@@ -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 )
arch/x86/kvm/x86.c void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr) · line 1182
Quoted 10 lines
arch/x86/kvm/x86.c +6
-1- 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
--
Gleb.