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KVM provides the KVM_SET_TSC_KHZ VM > scope ioctl to allow the userspace VMM to configure the TSC of such VM. > After that the userspace VMM is not supposed to call the KVM_SET_TSC_KHZ > vCPU scope ioctl anymore when creating the vCPU. > > The de facto userspace VMM Qemu does this for TDX guests. The upcoming > SEV-SNP guests with Secure TSC should follow. > > Note this could be a break of ABI. But for now only TDX guests are TSC > protected and only Qemu supports TDX, thus in practice this should not > break any existing userspace. > > Suggested-by: Sean Christopherson > Signed-off-by: Kai Huang Need to add this in Documentation/virt/kvm/api.rst as well, saying that for TDX and SecureTSC enabled SNP guests, KVM_SET_TSC_KHZ vCPU ioctl is not valid. > --- > 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 2806f7104295..699ca5e74bba 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -6186,6 +6186,10 @@ long kvm_arch_vcpu_ioctl(struct file *filp, > u32 user_tsc_khz; > > r = -EINVAL; > + > + if (vcpu->arch.guest_tsc_protected) > + goto out; > + > user_tsc_khz = (u32)arg; > > if (kvm_caps.has_tsc_control && Regards Nikunj