linux-kernel - [RFC PATCH 1/7] KVM: x86: Move shared CET routine to common x86 kvm code

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Date:   Wed, 12 Oct 2022 20:39:04 +0000
From:   John Allen <john.allen@....com>
To:     <kvm@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <pbonzini@...hat.com>,
        <weijiang.yang@...el.com>, <rick.p.edgecombe@...el.com>,
        <seanjc@...gle.com>, <x86@...nel.org>, <thomas.lendacky@....com>,
        John Allen <john.allen@....com>
Subject: [RFC PATCH 1/7] KVM: x86: Move shared CET routine to common x86 kvm code

cet_is_msr_accessible can also by used for shadow stack support in SVM.
Move this to common x86 kvm code.

Signed-off-by: John Allen <john.allen@....com>
---
 arch/x86/kvm/vmx/vmx.c | 32 +++-----------------------------
 arch/x86/kvm/x86.c     | 26 ++++++++++++++++++++++++++
 arch/x86/kvm/x86.h     |  2 ++
 3 files changed, 31 insertions(+), 29 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 4558b13d0610..8b79a727b29c 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1845,32 +1845,6 @@ static int vmx_get_msr_feature(struct kvm_msr_entry *msr)
 	}
 }
 
-static bool cet_is_msr_accessible(struct kvm_vcpu *vcpu,
-				  struct msr_data *msr)
-{
-	if (!kvm_cet_user_supported() &&
-	    !cet_kernel_ibt_supported())
-		return false;
-
-	if (msr->host_initiated)
-		return true;
-
-	if (!guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) &&
-	    !guest_cpuid_has(vcpu, X86_FEATURE_IBT))
-		return false;
-
-	if (msr->index == MSR_IA32_S_CET &&
-	    guest_cpuid_has(vcpu, X86_FEATURE_IBT))
-		return true;
-
-	if ((msr->index == MSR_IA32_PL3_SSP ||
-	     msr->index == MSR_KVM_GUEST_SSP) &&
-	    !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK))
-		return false;
-
-	return true;
-}
-
 /*
  * Reads an msr value (of 'msr_info->index') into 'msr_info->data'.
  * Returns 0 on success, non-0 otherwise.
@@ -2014,7 +1988,7 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_IA32_PL3_SSP:
 	case MSR_KVM_GUEST_SSP:
 	case MSR_IA32_S_CET:
-		if (!cet_is_msr_accessible(vcpu, msr_info))
+		if (!kvm_cet_is_msr_accessible(vcpu, msr_info))
 			return 1;
 		if (msr_info->index == MSR_KVM_GUEST_SSP)
 			msr_info->data = vmcs_readl(GUEST_SSP);
@@ -2363,7 +2337,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		break;
 	case MSR_IA32_U_CET:
 	case MSR_IA32_S_CET:
-		if (!cet_is_msr_accessible(vcpu, msr_info))
+		if (!kvm_cet_is_msr_accessible(vcpu, msr_info))
 			return 1;
 		if ((data & GENMASK(9, 6)) ||
 		    is_noncanonical_address(data, vcpu))
@@ -2375,7 +2349,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		break;
 	case MSR_IA32_PL3_SSP:
 	case MSR_KVM_GUEST_SSP:
-		if (!cet_is_msr_accessible(vcpu, msr_info))
+		if (!kvm_cet_is_msr_accessible(vcpu, msr_info))
 			return 1;
 		if ((data & GENMASK(2, 0)) ||
 		    is_noncanonical_address(data, vcpu))
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5786225c0dfa..486e91f4a538 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -13475,6 +13475,32 @@ int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size,
 }
 EXPORT_SYMBOL_GPL(kvm_sev_es_string_io);
 
+bool kvm_cet_is_msr_accessible(struct kvm_vcpu *vcpu, struct msr_data *msr)
+{
+	if (!kvm_cet_user_supported() &&
+	    !cet_kernel_ibt_supported())
+		return false;
+
+	if (msr->host_initiated)
+		return true;
+
+	if (!guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) &&
+	    !guest_cpuid_has(vcpu, X86_FEATURE_IBT))
+		return false;
+
+	if (msr->index == MSR_IA32_S_CET &&
+	    guest_cpuid_has(vcpu, X86_FEATURE_IBT))
+		return true;
+
+	if ((msr->index == MSR_IA32_PL3_SSP ||
+	     msr->index == MSR_KVM_GUEST_SSP) &&
+	    !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK))
+		return false;
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(kvm_cet_is_msr_accessible);
+
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_entry);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio);
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index a55f262d1e61..fb871be7131e 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -502,6 +502,8 @@ int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size,
 			 unsigned int port, void *data,  unsigned int count,
 			 int in);
 
+bool kvm_cet_is_msr_accessible(struct kvm_vcpu *vcpu, struct msr_data *msr);
+
 /*
  * We've already loaded guest MSRs in __msr_io() when check the MSR index.
  * In case vcpu has been preempted, we need to disable preemption, check
-- 
2.34.3