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

Chao Gao
2024-04-03T06:51:25Z

On Mon, Feb 26, 2024 at 12:26:53AM -0800, isaku.yamahata@intel.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.