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

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Date:   Thu, 15 Dec 2022 17:39:52 -0800
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     "Huang, Kai" <kai.huang@...el.com>
Cc:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "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 Wed, Dec 14, 2022 at 11:22:02AM +0000,
"Huang, Kai" <kai.huang@...el.com> wrote:

> 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.

Makes sense. updated as follows.

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index ee8d395af849..b4132167e2bb 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1606,6 +1606,17 @@ void tdx_get_exit_info(struct kvm_vcpu *vcpu, u32 *reason,
        *error_code = 0;
 }
 
+static bool tdx_is_emulated_kvm_msr(u32 index, bool write)
+{
+       switch (index) {
+       case MSR_KVM_STEAL_TIME:
+       case MSR_KVM_POLL_CONTROL:
+               return true;
+       default:
+               return false;
+       }
+}
+
 bool tdx_is_emulated_msr(u32 index, bool write)
 {
        switch (index) {
@@ -1619,8 +1630,6 @@ bool tdx_is_emulated_msr(u32 index, bool write)
        case MSR_MTRRdefType:
        case MSR_IA32_TSC_DEADLINE:
        case MSR_IA32_MISC_ENABLE:
-       case MSR_KVM_STEAL_TIME:
-       case MSR_KVM_POLL_CONTROL:
        case MSR_PLATFORM_INFO:
        case MSR_MISC_FEATURES_ENABLES:
        case MSR_IA32_MCG_CAP:
@@ -1650,6 +1659,9 @@ bool tdx_is_emulated_msr(u32 index, bool write)
        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;
        }
-- 
Isaku Yamahata <isaku.yamahata@...il.com>