[PATCH 2/4] target/i386: Add CET MSRs access interfaces

[Yang Weijiang <weijiang.yang@xxxxxxxxx>]

Add access interfaces for supported CET MSRs.
These CET MSRs include:
MSR_IA32_U_CET - store user mode CET control bits.
MSR_IA32_S_CET - store supervisor mode CET control bits.
MSR_IA32_PL3_SSP - strore user mode shadow stack pointer.
MSR_KVM_GUEST_SSP - store current shadow stack pointer.

Other MSRs, i.e., MSR_IA32_PL{0,1,2}_SSP and MSR_IA32_INTR_SSP_TBL
are for non-supported supervisor mode shadow stack, are ignored now.

Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
 target/i386/cpu.h     | 10 ++++++++++
 target/i386/kvm/kvm.c | 44 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 6526a03206..b78ce8e5c4 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -545,6 +545,11 @@ typedef enum X86Seg {
 #define MSR_IA32_VMX_TRUE_ENTRY_CTLS     0x00000490
 #define MSR_IA32_VMX_VMFUNC             0x00000491
 
+#define MSR_IA32_U_CET                  0x000006a0
+#define MSR_IA32_S_CET                  0x000006a2
+#define MSR_IA32_PL3_SSP                0x000006a7
+#define MSR_KVM_GUEST_SSP               0x4b564d09
+
 #define XSTATE_FP_BIT                   0
 #define XSTATE_SSE_BIT                  1
 #define XSTATE_YMM_BIT                  2
@@ -1756,6 +1761,11 @@ typedef struct CPUArchState {
 
     uintptr_t retaddr;
 
+    uint64_t u_cet;
+    uint64_t s_cet;
+    uint64_t pl3_ssp;
+    uint64_t guest_ssp;
+
     /* Fields up to this point are cleared by a CPU reset */
     struct {} end_reset_fields;
 
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index de531842f6..13fae898ce 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -3646,6 +3646,22 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
         }
     }
 
+    if (((env->features[FEAT_7_0_ECX] & CPUID_7_0_ECX_CET_SHSTK) ||
+        (env->features[FEAT_7_0_EDX] & CPUID_7_0_EDX_CET_IBT)) &&
+        (env->features[FEAT_XSAVE_XSS_LO] & XSTATE_CET_U_MASK)) {
+        kvm_msr_entry_add(cpu, MSR_IA32_U_CET, env->u_cet);
+        kvm_msr_entry_add(cpu, MSR_IA32_PL3_SSP, env->pl3_ssp);
+    }
+
+    if ((env->features[FEAT_7_0_ECX] & CPUID_7_0_ECX_CET_SHSTK) &&
+        (env->features[FEAT_XSAVE_XSS_LO] & XSTATE_CET_U_MASK)) {
+        kvm_msr_entry_add(cpu, MSR_KVM_GUEST_SSP, env->guest_ssp);
+    }
+
+    if (env->features[FEAT_7_0_EDX] & CPUID_7_0_EDX_CET_IBT) {
+        kvm_msr_entry_add(cpu, MSR_IA32_S_CET, env->s_cet);
+    }
+
     return kvm_buf_set_msrs(cpu);
 }
 
@@ -4024,6 +4040,22 @@ static int kvm_get_msrs(X86CPU *cpu)
         kvm_msr_entry_add(cpu, MSR_IA32_SGXLEPUBKEYHASH3, 0);
     }
 
+    if (((env->features[FEAT_7_0_ECX] & CPUID_7_0_ECX_CET_SHSTK) ||
+        (env->features[FEAT_7_0_EDX] & CPUID_7_0_EDX_CET_IBT)) &&
+        (env->features[FEAT_XSAVE_XSS_LO] & XSTATE_CET_U_MASK)) {
+        kvm_msr_entry_add(cpu, MSR_IA32_U_CET, 0);
+        kvm_msr_entry_add(cpu, MSR_IA32_PL3_SSP, 0);
+    }
+
+    if ((env->features[FEAT_7_0_ECX] & CPUID_7_0_ECX_CET_SHSTK) &&
+        (env->features[FEAT_XSAVE_XSS_LO] & XSTATE_CET_U_MASK)) {
+        kvm_msr_entry_add(cpu, MSR_KVM_GUEST_SSP, 0);
+    }
+
+    if (env->features[FEAT_7_0_EDX] & CPUID_7_0_EDX_CET_IBT) {
+        kvm_msr_entry_add(cpu, MSR_IA32_S_CET, 0);
+    }
+
     if (env->features[FEAT_XSAVE] & CPUID_D_1_EAX_XFD) {
         kvm_msr_entry_add(cpu, MSR_IA32_XFD, 0);
         kvm_msr_entry_add(cpu, MSR_IA32_XFD_ERR, 0);
@@ -4346,6 +4378,18 @@ static int kvm_get_msrs(X86CPU *cpu)
             env->msr_ia32_sgxlepubkeyhash[index - MSR_IA32_SGXLEPUBKEYHASH0] =
                            msrs[i].data;
             break;
+        case MSR_IA32_U_CET:
+            env->u_cet = msrs[i].data;
+            break;
+        case MSR_IA32_S_CET:
+            env->s_cet = msrs[i].data;
+            break;
+        case MSR_IA32_PL3_SSP:
+            env->pl3_ssp = msrs[i].data;
+            break;
+        case MSR_KVM_GUEST_SSP:
+            env->guest_ssp = msrs[i].data;
+            break;
         case MSR_IA32_XFD:
             env->msr_xfd = msrs[i].data;
             break;
-- 
2.27.0