[Qemu-devel][PATCH v6 4/6] x86/cpu: Add user-space MSR access interface for CET

[Yang Weijiang]

CET states are divided into user-mode and supervisor-mode states,
MSR_KVM_GUEST_SSP stores current SHSTK pointer in use, MSR_IA32_U_CET and
MSR_IA32_PL3_SSP are for user-mode states, others are for supervisor-mode
states. Expose the access according to current CET supported bits in CPUID
and XSS.

Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
 target/i386/cpu.h | 18 ++++++++++++
 target/i386/kvm.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+)

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index d4563fa0e8..9c0568672e 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -484,6 +484,15 @@ typedef enum X86Seg {
 #define MSR_IA32_VMX_TRUE_ENTRY_CTLS     0x00000490
 #define MSR_IA32_VMX_VMFUNC             0x00000491
 
+#define MSR_IA32_U_CET                  0x6a0
+#define MSR_IA32_S_CET                  0x6a2
+#define MSR_IA32_PL0_SSP                0x6a4
+#define MSR_IA32_PL1_SSP                0x6a5
+#define MSR_IA32_PL2_SSP                0x6a6
+#define MSR_IA32_PL3_SSP                0x6a7
+#define MSR_IA32_SSP_TBL                0x6a8
+#define MSR_KVM_GUEST_SSP               0x4b564d06
+
 #define XSTATE_FP_BIT                   0
 #define XSTATE_SSE_BIT                  1
 #define XSTATE_YMM_BIT                  2
@@ -1583,6 +1592,15 @@ typedef struct CPUX86State {
 
     uintptr_t retaddr;
 
+    uint64_t u_cet;
+    uint64_t s_cet;
+    uint64_t pl0_ssp;
+    uint64_t pl1_ssp;
+    uint64_t pl2_ssp;
+    uint64_t pl3_ssp;
+    uint64_t ssp_tbl;
+    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.c b/target/i386/kvm.c
index 6f18d940a5..3315d5dd4f 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -3001,6 +3001,31 @@ 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_XSAVE_XSS_LO] & XSTATE_CET_S_MASK) {
+        if (env->features[FEAT_7_0_ECX] & CPUID_7_0_ECX_CET_SHSTK) {
+            kvm_msr_entry_add(cpu, MSR_IA32_PL0_SSP, env->pl0_ssp);
+            kvm_msr_entry_add(cpu, MSR_IA32_PL1_SSP, env->pl1_ssp);
+            kvm_msr_entry_add(cpu, MSR_IA32_PL2_SSP, env->pl2_ssp);
+            kvm_msr_entry_add(cpu, MSR_IA32_SSP_TBL, env->ssp_tbl);
+        }
+
+        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);
+        }
+    }
+
+    if ((env->features[FEAT_7_0_ECX] & CPUID_7_0_ECX_CET_SHSTK) &&
+        (env->features[FEAT_XSAVE_XSS_LO] & (XSTATE_CET_U_MASK |
+        XSTATE_CET_S_MASK)))
+        kvm_msr_entry_add(cpu, MSR_KVM_GUEST_SSP, env->guest_ssp);
+
     return kvm_buf_set_msrs(cpu);
 }
 
@@ -3317,6 +3342,30 @@ static int kvm_get_msrs(X86CPU *cpu)
         }
     }
 
+    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_XSAVE_XSS_LO] & XSTATE_CET_S_MASK) {
+        if (env->features[FEAT_7_0_ECX] & CPUID_7_0_ECX_CET_SHSTK) {
+            kvm_msr_entry_add(cpu, MSR_IA32_PL0_SSP, 0);
+            kvm_msr_entry_add(cpu, MSR_IA32_PL1_SSP, 0);
+            kvm_msr_entry_add(cpu, MSR_IA32_PL2_SSP, 0);
+            kvm_msr_entry_add(cpu, MSR_IA32_SSP_TBL, 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_7_0_ECX] & CPUID_7_0_ECX_CET_SHSTK) &&
+        (env->features[FEAT_XSAVE_XSS_LO] & (XSTATE_CET_U_MASK |
+        XSTATE_CET_S_MASK)))
+        kvm_msr_entry_add(cpu, MSR_KVM_GUEST_SSP, 0);
+
     ret = kvm_vcpu_ioctl(CPU(cpu), KVM_GET_MSRS, cpu->kvm_msr_buf);
     if (ret < 0) {
         return ret;
@@ -3600,6 +3649,30 @@ static int kvm_get_msrs(X86CPU *cpu)
         case MSR_IA32_RTIT_ADDR0_A ... MSR_IA32_RTIT_ADDR3_B:
             env->msr_rtit_addrs[index - MSR_IA32_RTIT_ADDR0_A] = 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_PL0_SSP:
+            env->pl0_ssp = msrs[i].data;
+            break;
+        case MSR_IA32_PL1_SSP:
+            env->pl1_ssp = msrs[i].data;
+            break;
+        case MSR_IA32_PL2_SSP:
+            env->pl2_ssp = msrs[i].data;
+            break;
+        case MSR_IA32_PL3_SSP:
+            env->pl3_ssp = msrs[i].data;
+            break;
+        case MSR_IA32_SSP_TBL:
+            env->ssp_tbl = msrs[i].data;
+            break;
+        case MSR_KVM_GUEST_SSP:
+            env->guest_ssp = msrs[i].data;
+            break;
         }
     }
 
-- 
2.26.2