linux-kernel - Re: [PATCH v10 098/108] KVM: TDX: Implement callbacks for MSR operations for TDX

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Date:   Wed, 14 Dec 2022 11:22:02 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>
CC:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "Aktas, Erdem" <erdemaktas@...gle.com>,
        "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>
Subject: Re: [PATCH v10 098/108] KVM: TDX: Implement callbacks for MSR
 operations for TDX

On Sat, 2022-10-29 at 23:23 -0700, isaku.yamahata@...el.com wrote:
> +bool tdx_is_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_MTRRcap:
> +	case 0x200 ... 0x26f:
> +		/* IA32_MTRR_PHYS{BASE, MASK}, IA32_MTRR_FIX*_* */
> +	case MSR_IA32_CR_PAT:
> +	case MSR_MTRRdefType:
> +	case MSR_IA32_TSC_DEADLINE:
> +	case MSR_IA32_MISC_ENABLE:
> +	case MSR_KVM_STEAL_TIME:
> +	case MSR_KVM_POLL_CONTROL:

To me putting KVM para-virt MSRs and hardware MSRs together isn't good idea. 
You can introduce separate helpers for them.

> +	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;
> +	default:
> +		return false;
> +	}
> +}