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Probably the below is clear: Reject KVM_SET_TSC_KHZ VM ioctl when vCPUs have been created > > The VM scope KVM_SET_TSC_KHZ ioctl is used to set up the default TSC > frequency that all subsequent created vCPUs use. It is only intended to > be called before any vCPU is created. Allowing it to be called after > that only results in confusion but nothing good. > > Note this is an ABI change. But currently in Qemu (the de facto > userspace VMM) only TDX uses this VM ioctl, and it is only called once > before creating any vCPU, therefore the risk of breaking userspace is > pretty low. > > Suggested-by: Sean Christopherson > Signed-off-by: Kai Huang Reviewed-by: Nikunj A Dadhania > --- > arch/x86/kvm/x86.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 699ca5e74bba..e5e55d549468 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -7194,6 +7194,10 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) > u32 user_tsc_khz; > > r = -EINVAL; > + > + if (kvm->created_vcpus) > + goto out; > + > user_tsc_khz = (u32)arg; > > if (kvm_caps.has_tsc_control &&