Re: [PATCH v3 07/27] KVM: VMX: Initialize VMCS FRED fields

[Chao Gao <chao.gao@intel.com>]

>@@ -1503,6 +1503,18 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu,
> 				    (unsigned long)(cpu_entry_stack(cpu) + 1));
> 		}
> 
>+		/* Per-CPU FRED MSRs */
>+		if (kvm_cpu_cap_has(X86_FEATURE_FRED)) {
>+#ifdef CONFIG_X86_64
>+			vmcs_write64(HOST_IA32_FRED_RSP1, __this_cpu_ist_top_va(DB));
>+			vmcs_write64(HOST_IA32_FRED_RSP2, __this_cpu_ist_top_va(NMI));
>+			vmcs_write64(HOST_IA32_FRED_RSP3, __this_cpu_ist_top_va(DF));
>+#endif
>+			vmcs_write64(HOST_IA32_FRED_SSP1, 0);
>+			vmcs_write64(HOST_IA32_FRED_SSP2, 0);
>+			vmcs_write64(HOST_IA32_FRED_SSP3, 0);

Given SSP[1-3] are constant for now, how about asserting that host SSP[1-3] are
all zeros when KVM is loaded and moving their writes to vmx_set_constant_host_state()?

>+		}
>+
> 		vmx->loaded_vmcs->cpu = cpu;
> 	}
> }
>@@ -4366,6 +4378,12 @@ void vmx_set_constant_host_state(struct vcpu_vmx *vmx)
> 	 */
> 	vmcs_write16(HOST_DS_SELECTOR, 0);
> 	vmcs_write16(HOST_ES_SELECTOR, 0);
>+
>+	/* FRED CONFIG and STKLVLS are the same on all CPUs. */
>+	if (kvm_cpu_cap_has(X86_FEATURE_FRED)) {
>+		vmcs_write64(HOST_IA32_FRED_CONFIG, kvm_host.fred_config);
>+		vmcs_write64(HOST_IA32_FRED_STKLVLS, kvm_host.fred_stklvls);
>+	}
> #else
> 	vmcs_write16(HOST_DS_SELECTOR, __KERNEL_DS);  /* 22.2.4 */
> 	vmcs_write16(HOST_ES_SELECTOR, __KERNEL_DS);  /* 22.2.4 */