linux-kernel - [PATCH v4 14/20] KVM:VMX: Set up interception for CET MSRs

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Date:   Thu, 20 Jul 2023 23:03:46 -0400
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     seanjc@...gle.com, pbonzini@...hat.com, peterz@...radead.org,
        john.allen@....com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     rick.p.edgecombe@...el.com, chao.gao@...el.com,
        binbin.wu@...ux.intel.com, weijiang.yang@...el.com
Subject: [PATCH v4 14/20] KVM:VMX: Set up interception for CET MSRs

Pass through CET MSRs when the associated feature is enabled.
Shadow Stack feature requires all the CET MSRs to make it
architectural support in guest. IBT feature only depends on
MSR_IA32_U_CET and MSR_IA32_S_CET to enable both user and
supervisor IBT.

Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index b29817ec6f2e..85cb7e748a89 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -709,6 +709,10 @@ static bool is_valid_passthrough_msr(u32 msr)
 	case MSR_LBR_CORE_TO ... MSR_LBR_CORE_TO + 8:
 		/* LBR MSRs. These are handled in vmx_update_intercept_for_lbr_msrs() */
 		return true;
+	case MSR_IA32_U_CET:
+	case MSR_IA32_S_CET:
+	case MSR_IA32_PL0_SSP ... MSR_IA32_INT_SSP_TAB:
+		return true;
 	}
 
 	r = possible_passthrough_msr_slot(msr) != -ENOENT;
@@ -7758,6 +7762,34 @@ static void update_intel_pt_cfg(struct kvm_vcpu *vcpu)
 		vmx->pt_desc.ctl_bitmask &= ~(0xfULL << (32 + i * 4));
 }
 
+static void vmx_update_intercept_for_cet_msr(struct kvm_vcpu *vcpu)
+{
+	if (guest_can_use(vcpu, X86_FEATURE_SHSTK)) {
+		vmx_set_intercept_for_msr(vcpu, MSR_IA32_U_CET,
+					  MSR_TYPE_RW, false);
+		vmx_set_intercept_for_msr(vcpu, MSR_IA32_S_CET,
+					  MSR_TYPE_RW, false);
+		vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL0_SSP,
+					  MSR_TYPE_RW, false);
+		vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL1_SSP,
+					  MSR_TYPE_RW, false);
+		vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL2_SSP,
+					  MSR_TYPE_RW, false);
+		vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL3_SSP,
+					  MSR_TYPE_RW, false);
+		vmx_set_intercept_for_msr(vcpu, MSR_IA32_INT_SSP_TAB,
+					  MSR_TYPE_RW, false);
+		return;
+	}
+
+	if (guest_can_use(vcpu, X86_FEATURE_IBT)) {
+		vmx_set_intercept_for_msr(vcpu, MSR_IA32_U_CET,
+					  MSR_TYPE_RW, false);
+		vmx_set_intercept_for_msr(vcpu, MSR_IA32_S_CET,
+					  MSR_TYPE_RW, false);
+	}
+}
+
 static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -7825,6 +7857,9 @@ static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 
 	/* Refresh #PF interception to account for MAXPHYADDR changes. */
 	vmx_update_exception_bitmap(vcpu);
+
+	if (kvm_is_cet_supported())
+		vmx_update_intercept_for_cet_msr(vcpu);
 }
 
 static u64 vmx_get_perf_capabilities(void)
-- 
2.27.0