Messages in this thread | | | Subject | Re: [PATCH 6/6] KVM: VMX: enable IPI virtualization | From | Zeng Guang <> | Date | Mon, 19 Jul 2021 21:16:59 +0800 |
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On 7/19/2021 4:32 AM, Paolo Bonzini wrote: > On 17/07/21 05:55, Zeng Guang wrote: >>>> + if (vmx->ipiv_active) >>>> + install_pid(vmx); >>> This should be if (enable_ipiv) instead, I think. >>> >>> In fact, in all other places that are using vmx->ipiv_active, you can >>> actually replace it with enable_ipiv; they are all reached only with >>> kvm_vcpu_apicv_active(vcpu) == true. >>> >> enable_ipiv as a global variable indicates the hardware capability to >> enable IPIv. Each VM may have different IPIv configuration according to >> kvm_vcpu_apicv_active status. So we use ipiv_active per VM to enclose >> IPIv related operations. > Understood, but in practice all uses of vmx->ipiv_active are guarded by > kvm_vcpu_apicv_active so they are always reached with vmx->ipiv_active > == enable_ipiv. > > The one above instead seems wrong and should just use enable_ipiv. enable_ipiv associate with "IPI virtualization" setting in tertiary exec controls and enable_apicv which depends on cpu_has_vmx_apicv(). kvm_vcpu_apicv_active still can be false even if enable_ipiv is true, e.g. in case irqchip not emulated in kernel.
Though it's ok to use enable_ipiv here, vmcs setup succeed for IPIv but it won't take into effect as false kvm_vcpu_apicv_active runtime disable “IPI virtualization" for VM in this case and leads vmx->ipiv_active become false as well. So vmx->ipiv_active is more accurate to reflect runtime IPIv status. > Paolo >
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