linux-kernel - [PATCH v15 11/14] KVM: VMX: Pass through CET MSRs to the guest when supported

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Message-Id: <20210203113421.5759-12-weijiang.yang@intel.com>
Date:   Wed,  3 Feb 2021 19:34:18 +0800
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     pbonzini@...hat.com, seanjc@...gle.com, jmattson@...gle.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     yu.c.zhang@...ux.intel.com, Yang Weijiang <weijiang.yang@...el.com>
Subject: [PATCH v15 11/14] KVM: VMX: Pass through CET MSRs to the guest when supported

Pass through all CET MSRs when the associated CET component (kernel vs.
user) is enabled to improve guest performance.  All CET MSRs are context
switched, either via dedicated VMCS fields or XSAVES.

Co-developed-by: Zhang Yi Z <yi.z.zhang@...ux.intel.com>
Signed-off-by: Zhang Yi Z <yi.z.zhang@...ux.intel.com>
Co-developed-by: Sean Christopherson <sean.j.christopherson@...el.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c2242fc1f71a..b6657117191b 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -659,6 +659,10 @@ static bool is_valid_passthrough_msr(u32 msr)
 	case MSR_IA32_RTIT_ADDR0_A ... MSR_IA32_RTIT_ADDR3_B:
 		/* PT MSRs. These are handled in pt_update_intercept_for_msr() */
 		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;
@@ -7343,6 +7347,32 @@ static void update_intel_pt_cfg(struct kvm_vcpu *vcpu)
 		vmx->pt_desc.ctl_bitmask &= ~(0xfULL << (32 + i * 4));
 }
 
+static bool is_cet_state_supported(struct kvm_vcpu *vcpu, u32 xss_state)
+{
+	return (vcpu->arch.guest_supported_xss & xss_state) &&
+	       (guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) ||
+		guest_cpuid_has(vcpu, X86_FEATURE_IBT));
+}
+
+static void vmx_update_intercept_for_cet_msr(struct kvm_vcpu *vcpu)
+{
+	bool incpt = !is_cet_state_supported(vcpu, XFEATURE_MASK_CET_USER);
+
+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_U_CET, MSR_TYPE_RW, incpt);
+
+	incpt |= !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK);
+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL3_SSP, MSR_TYPE_RW, incpt);
+
+	incpt = !is_cet_state_supported(vcpu, XFEATURE_MASK_CET_KERNEL);
+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_S_CET, MSR_TYPE_RW, incpt);
+
+	incpt |= !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK);
+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_INT_SSP_TAB, MSR_TYPE_RW, incpt);
+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL0_SSP, MSR_TYPE_RW, incpt);
+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL1_SSP, MSR_TYPE_RW, incpt);
+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL2_SSP, MSR_TYPE_RW, incpt);
+}
+
 static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -7386,6 +7416,9 @@ static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 
 	/* Refresh #PF interception to account for MAXPHYADDR changes. */
 	update_exception_bitmap(vcpu);
+
+	if (kvm_cet_supported())
+		vmx_update_intercept_for_cet_msr(vcpu);
 }
 
 static __init void vmx_set_cpu_caps(void)
-- 
2.26.2