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
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