On 2011-12-21 11:44, Avi Kivity wrote: > On 12/21/2011 12:41 PM, Jan Kiszka wrote: >> On 2011-12-21 11:35, Avi Kivity wrote: >>> On 12/21/2011 12:25 PM, Jan Kiszka wrote: >>>> We must not report the TSC deadline timer feature on our own when user >>>> space provides the APIC as we have no clue about its features. >>> >>> We must not report the TSC deadline timer feature on our own, period. >>> We should just update the timer mode mask there. Don't know how this >>> slipped through review. >>> >>> I think your original idea was correct. Add a new KVM_CAP for the tsc >>> deadline timer. Userspace can add the bit to cpuid if either it >>> implements the feature in a userspace apic, or if it finds the new >>> capability and uses the kernel apic. >> >> Right, we do need some control for user space to keep the feature >> disabled when migrating from an older host. >> >> However, there is also the timer_mode_mask which requires tuning in >> addition to the cpuid flag. >> > > timer_mode_mask can just be slaved to the bit (as received by > KVM_SET_CPUID); that's exactly kvm_update_cpuid()'s role. Like diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 230f713..89b02bf 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -27,7 +27,6 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu) { struct kvm_cpuid_entry2 *best; struct kvm_lapic *apic = vcpu->arch.apic; - u32 timer_mode_mask; best = kvm_find_cpuid_entry(vcpu, 1, 0); if (!best) @@ -40,15 +39,12 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu) best->ecx |= bit(X86_FEATURE_OSXSAVE); } - if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL && - best->function == 0x1) { - best->ecx |= bit(X86_FEATURE_TSC_DEADLINE_TIMER); - timer_mode_mask = 3 << 17; - } else - timer_mode_mask = 1 << 17; - - if (apic) - apic->lapic_timer.timer_mode_mask = timer_mode_mask; + if (apic) { + if (best->ecx & bit(X86_FEATURE_TSC_DEADLINE_TIMER)) + apic->lapic_timer.timer_mode_mask = 3 << 17; + else + apic->lapic_timer.timer_mode_mask = 1 << 17; + } kvm_pmu_cpuid_update(vcpu); } + the KVM_CAP thing? Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html