linux-kernel - RE: [PATCH v1 08/23] KVM: VMX: Initialize VMCS FRED fields

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Message-ID: <SA1PR11MB6734E58758C5611087B5E688A8B2A@SA1PR11MB6734.namprd11.prod.outlook.com>
Date:   Tue, 14 Nov 2023 06:02:01 +0000
From:   "Li, Xin3" <xin3.li@...el.com>
To:     "Gao, Chao" <chao.gao@...el.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
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        "corbet@....net" <corbet@....net>,
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        "Shankar, Ravi V" <ravi.v.shankar@...el.com>
Subject: RE: [PATCH v1 08/23] KVM: VMX: Initialize VMCS FRED fields

> >@@ -1477,6 +1477,18 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int
> cpu,
> > 				    (unsigned long)(cpu_entry_stack(cpu) + 1));
> > 		}
> >
> >+#ifdef CONFIG_X86_64
> >+		/* Per-CPU FRED MSRs */
> >+		if (cpu_feature_enabled(X86_FEATURE_FRED)) {
> 
> how about kvm_cpu_cap_has()? to decouple KVM's capability to virtualize a feature
> and host's enabling a feature.

Very likely I guess.

> >+			vmcs_write64(HOST_IA32_FRED_RSP1,
> read_msr(MSR_IA32_FRED_RSP1));
> >+			vmcs_write64(HOST_IA32_FRED_RSP2,
> read_msr(MSR_IA32_FRED_RSP2));
> >+			vmcs_write64(HOST_IA32_FRED_RSP3,
> read_msr(MSR_IA32_FRED_RSP3));
> >+			vmcs_write64(HOST_IA32_FRED_SSP1,
> read_msr(MSR_IA32_FRED_SSP1));
> >+			vmcs_write64(HOST_IA32_FRED_SSP2,
> read_msr(MSR_IA32_FRED_SSP2));
> >+			vmcs_write64(HOST_IA32_FRED_SSP3,
> read_msr(MSR_IA32_FRED_SSP3));
> >+		}
> >+#endif
> 
> why is this hunk enclosed in #ifdef CONFIG_X86_64 while the one below isn't?

As if the compiler doesn't complain, I should NOT add it.

> 
> >+	if (cpu_feature_enabled(X86_FEATURE_FRED)) {
> >+		vmcs_write64(GUEST_IA32_FRED_CONFIG, 0);
> >+		vmcs_write64(GUEST_IA32_FRED_RSP1, 0);
> >+		vmcs_write64(GUEST_IA32_FRED_RSP2, 0);
> >+		vmcs_write64(GUEST_IA32_FRED_RSP3, 0);
> >+		vmcs_write64(GUEST_IA32_FRED_STKLVLS, 0);
> >+		vmcs_write64(GUEST_IA32_FRED_SSP1, 0);
> >+		vmcs_write64(GUEST_IA32_FRED_SSP2, 0);
> >+		vmcs_write64(GUEST_IA32_FRED_SSP3, 0);
> >+	}
> >+
> 
> move this hunk to __vmx_vcpu_reset() because FRED spec says
> 
> "INIT does not change the value of the new MSRs."
> 

Yeah, will do.