Re: [PATCH 6/6] KVM: VMX: enable IPI virtualization

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On 7/16/2021 5:52 PM, Paolo Bonzini wrote:
On 16/07/21 08:48, Zeng Guang wrote:

+    if (!(_cpu_based_3rd_exec_control & TERTIARY_EXEC_IPI_VIRT))
+        enable_ipiv = 0;
+
      }

Please move this to hardware_setup(), using a new function cpu_has_vmx_ipiv() in vmx/capabilities.h.

ok, we will change it to follow current framework.
     if (_cpu_based_exec_control & CPU_BASED_ACTIVATE_TERTIARY_CONTROLS) {
-        u64 opt3 = 0;
+        u64 opt3 = enable_ipiv ? TERTIARY_EXEC_IPI_VIRT : 0;
         u64 min3 = 0;

I like the idea of changing opt3, but it's different from how setup_vmcs_config works for the other execution controls.  Let me think if it makes sense to clean this up, and move the handling of other module parameters from hardware_setup() to setup_vmcs_config().

May be an exception for ipiv feature ?
+
+    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.
+    if (!enable_apicv) {
+        enable_ipiv = 0;
+        vmcs_config.cpu_based_3rd_exec_ctrl &= ~TERTIARY_EXEC_IPI_VIRT;
+    }

The assignment to vmcs_config.cpu_based_3rd_exec_ctrl should not be necessary; kvm_vcpu_apicv_active will always be false in that case and IPI virtualization would never be enabled.

We originally intend to make vmcs_config consistent with the actual ipiv capability and decouple it from other factors. As you mentioned , it's not necessary to update vmcs_config.cpu_based_3rd_exec_ctrl in this case. We will remove it.

Thanks.

Paolo




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