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SubjectRe: [PATCH v2] KVM x86/xen: add an override for PVCLOCK_TSC_STABLE_BIT
On 31/10/2023 23:06, David Woodhouse wrote:
[snip]
>>                 mutex_lock(&kvm->lock);
>>                 if (!kvm->created_vcpus) {
>>                         kvm->arch.force_tsc_unstable = true;
>>                         r = 0;
>>                 }
>>                 mutex_unlock(&kvm->lock);
>>
>> So that it would be blatantly obvious that there's no race with checking a per-VM
>> flag without any lock/RCU protections.
>
> Makes sense. Although TBH if the VMM wants to flip this bit on and off
> at runtime while the guest clocks are being updated, it deserves what
> it gets. It's not a problem for KVM.
>

The first version of the patch that used an attribute requested a clock
update when the attribute was set. I dropped that in this version but I
think it'd best to re-instate it.

Paul

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