linux-kernel - Re: [PATCH v19 111/130] KVM: TDX: Implement callbacks for MSR operations for TDX

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Date: Wed, 3 Apr 2024 14:51:12 +0800
From: Chao Gao <chao.gao@...el.com>
To: <isaku.yamahata@...el.com>
CC: <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<isaku.yamahata@...il.com>, Paolo Bonzini <pbonzini@...hat.com>,
	<erdemaktas@...gle.com>, Sean Christopherson <seanjc@...gle.com>, Sagi Shahar
	<sagis@...gle.com>, Kai Huang <kai.huang@...el.com>, <chen.bo@...el.com>,
	<hang.yuan@...el.com>, <tina.zhang@...el.com>
Subject: Re: [PATCH v19 111/130] KVM: TDX: Implement callbacks for MSR
 operations for TDX

On Mon, Feb 26, 2024 at 12:26:53AM -0800, isaku.yamahata@...el.com wrote:
>+bool tdx_has_emulated_msr(u32 index, bool write)
>+{
>+	switch (index) {
>+	case MSR_IA32_UCODE_REV:
>+	case MSR_IA32_ARCH_CAPABILITIES:
>+	case MSR_IA32_POWER_CTL:
>+	case MSR_IA32_CR_PAT:
>+	case MSR_IA32_TSC_DEADLINE:
>+	case MSR_IA32_MISC_ENABLE:
>+	case MSR_PLATFORM_INFO:
>+	case MSR_MISC_FEATURES_ENABLES:
>+	case MSR_IA32_MCG_CAP:
>+	case MSR_IA32_MCG_STATUS:
>+	case MSR_IA32_MCG_CTL:
>+	case MSR_IA32_MCG_EXT_CTL:
>+	case MSR_IA32_MC0_CTL ... MSR_IA32_MCx_CTL(KVM_MAX_MCE_BANKS) - 1:
>+	case MSR_IA32_MC0_CTL2 ... MSR_IA32_MCx_CTL2(KVM_MAX_MCE_BANKS) - 1:
>+		/* MSR_IA32_MCx_{CTL, STATUS, ADDR, MISC, CTL2} */
>+		return true;
>+	case APIC_BASE_MSR ... APIC_BASE_MSR + 0xff:
>+		/*
>+		 * x2APIC registers that are virtualized by the CPU can't be
>+		 * emulated, KVM doesn't have access to the virtual APIC page.
>+		 */
>+		switch (index) {
>+		case X2APIC_MSR(APIC_TASKPRI):
>+		case X2APIC_MSR(APIC_PROCPRI):
>+		case X2APIC_MSR(APIC_EOI):
>+		case X2APIC_MSR(APIC_ISR) ... X2APIC_MSR(APIC_ISR + APIC_ISR_NR):
>+		case X2APIC_MSR(APIC_TMR) ... X2APIC_MSR(APIC_TMR + APIC_ISR_NR):
>+		case X2APIC_MSR(APIC_IRR) ... X2APIC_MSR(APIC_IRR + APIC_ISR_NR):
>+			return false;
>+		default:
>+			return true;
>+		}
>+	case MSR_IA32_APICBASE:
>+	case MSR_EFER:
>+		return !write;
>+	case 0x4b564d00 ... 0x4b564dff:
>+		/* KVM custom MSRs */
>+		return tdx_is_emulated_kvm_msr(index, write);
>+	default:
>+		return false;
>+	}

The only call site with a non-Null KVM parameter is:

	r = static_call(kvm_x86_has_emulated_msr)(kvm, MSR_IA32_SMBASE);

Only MSR_IA32_SMBASE needs to be handled. So, this function is much more
complicated than it should be.