linux-kernel - [RFC PATCH v4 8/8] KVM:x86: Add user-space read/write interface for CET MSRs

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Message-Id: <20190318150351.15550-9-weijiang.yang@intel.com>
Date:   Mon, 18 Mar 2019 23:03:51 +0800
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     pbonzini@...hat.com, kvm@...r.kernel.org, mst@...hat.com,
        rkrcmar@...hat.com, jmattson@...gle.com,
        linux-kernel@...r.kernel.org, yu-cheng.yu@...el.com
Cc:     Yang Weijiang <weijiang.yang@...el.com>
Subject: [RFC PATCH v4 8/8] KVM:x86: Add user-space read/write interface for CET MSRs

When VMExit occurs, the Guest CET MSRs are stored in two different
places, U_CET/PL0_SSP/PL1_SSP/PL2_SSP/PL3_SSP are stored in fpu
xsave area, they are operated by XSAVES/XRSTORS, so before access
these MSRs, kvm_load_guest_fpu is required to restore them to Host MSRs.
After finish operation, need to restore Host MSRs by kvm_put_guest_fpu,
these two functions are call in __msr_io(). S_CET and INTR_SSP_TABLE
are stored in VMCS fields, so they can be access via vmcs_read/vmcs_write
directly.

Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
---
 arch/x86/include/asm/msr-index.h |  2 ++
 arch/x86/kvm/vmx.c               | 42 ++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 298721ff00f4..cc94ab14a946 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -782,6 +782,8 @@
 #define MSR_IA32_U_CET		0x6a0 /* user mode cet setting */
 #define MSR_IA32_S_CET		0x6a2 /* kernel mode cet setting */
 #define MSR_IA32_PL0_SSP	0x6a4 /* kernel shstk pointer */
+#define MSR_IA32_PL1_SSP	0x6a5 /* ring 1 shstk pointer */
+#define MSR_IA32_PL2_SSP	0x6a6 /* ring 2 shstk pointer */
 #define MSR_IA32_PL3_SSP	0x6a7 /* user shstk pointer */
 #define MSR_IA32_INT_SSP_TAB	0x6a8 /* exception shstk table */
 
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 816e11a66557..5923b89fe120 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4153,6 +4153,27 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 			return 1;
 		msr_info->data = vcpu->arch.ia32_xss;
 		break;
+	case MSR_IA32_S_CET:
+		msr_info->data = vmcs_readl(GUEST_S_CET);
+		break;
+	case MSR_IA32_U_CET:
+		rdmsrl(MSR_IA32_U_CET, msr_info->data);
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		msr_info->data = vmcs_readl(GUEST_INTR_SSP_TABLE);
+		break;
+	case MSR_IA32_PL0_SSP:
+		rdmsrl(MSR_IA32_PL0_SSP, msr_info->data);
+		break;
+	case MSR_IA32_PL1_SSP:
+		rdmsrl(MSR_IA32_PL1_SSP, msr_info->data);
+		break;
+	case MSR_IA32_PL2_SSP:
+		rdmsrl(MSR_IA32_PL2_SSP, msr_info->data);
+		break;
+	case MSR_IA32_PL3_SSP:
+		rdmsrl(MSR_IA32_PL3_SSP, msr_info->data);
+		break;
 	case MSR_TSC_AUX:
 		if (!msr_info->host_initiated &&
 		    !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
@@ -4337,6 +4358,27 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		else
 			clear_atomic_switch_msr(vmx, MSR_IA32_XSS);
 		break;
+	case MSR_IA32_S_CET:
+		vmcs_writel(GUEST_S_CET, data);
+		break;
+	case MSR_IA32_U_CET:
+		wrmsrl(MSR_IA32_U_CET, data);
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		vmcs_writel(GUEST_INTR_SSP_TABLE, data);
+		break;
+	case MSR_IA32_PL0_SSP:
+		wrmsrl(MSR_IA32_PL0_SSP, data);
+		break;
+	case MSR_IA32_PL1_SSP:
+		wrmsrl(MSR_IA32_PL1_SSP, data);
+		break;
+	case MSR_IA32_PL2_SSP:
+		wrmsrl(MSR_IA32_PL2_SSP, data);
+		break;
+	case MSR_IA32_PL3_SSP:
+		wrmsrl(MSR_IA32_PL3_SSP, data);
+		break;
 	case MSR_TSC_AUX:
 		if (!msr_info->host_initiated &&
 		    !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
-- 
2.17.1