x86: Enumeration for Control-flow Enforcement Technology

The CET spec has been published and guest kernels are starting to get support.
Introduce the CPUID and MSRs, and fully block the MSRs from guest use.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Wei Liu <wl@xen.org>

tools/libxl/libxl_cpuid.c

@@ -201,6 +201,7 @@ int libxl_cpuid_parse_config(libxl_cpuid_policy_list *cpuid, const char* str)
         {"pku",          0x00000007,  0, CPUID_REG_ECX,  3,  1},
         {"ospke",        0x00000007,  0, CPUID_REG_ECX,  4,  1},
         {"avx512-vbmi2", 0x00000007,  0, CPUID_REG_ECX,  6,  1},
+        {"cet-ss",       0x00000007,  0, CPUID_REG_ECX,  7,  1},
         {"gfni",         0x00000007,  0, CPUID_REG_ECX,  8,  1},
         {"vaes",         0x00000007,  0, CPUID_REG_ECX,  9,  1},
         {"vpclmulqdq",   0x00000007,  0, CPUID_REG_ECX, 10,  1},
@@ -213,6 +214,7 @@ int libxl_cpuid_parse_config(libxl_cpuid_policy_list *cpuid, const char* str)
         {"avx512-4vnniw",0x00000007,  0, CPUID_REG_EDX,  2,  1},
         {"avx512-4fmaps",0x00000007,  0, CPUID_REG_EDX,  3,  1},
         {"md-clear",     0x00000007,  0, CPUID_REG_EDX, 10,  1},
+        {"cet-ibt",      0x00000007,  0, CPUID_REG_EDX, 20,  1},
         {"ibrsb",        0x00000007,  0, CPUID_REG_EDX, 26,  1},
         {"stibp",        0x00000007,  0, CPUID_REG_EDX, 27,  1},
         {"l1d-flush",    0x00000007,  0, CPUID_REG_EDX, 28,  1},

tools/misc/xen-cpuid.c

@@ -123,7 +123,7 @@ static const char *const str_7c0[32] =
     [ 0] = "prefetchwt1",      [ 1] = "avx512_vbmi",
     [ 2] = "umip",             [ 3] = "pku",
     [ 4] = "ospke",            [ 5] = "waitpkg",
-    [ 6] = "avx512_vbmi2",
+    [ 6] = "avx512_vbmi2",     [ 7] = "cet-ss",
     [ 8] = "gfni",             [ 9] = "vaes",
     [10] = "vpclmulqdq",       [11] = "avx512_vnni",
     [12] = "avx512_bitalg",
@@ -163,6 +163,7 @@ static const char *const str_7d0[32] =
     /* 12 */                [13] = "tsx-force-abort",
 
     [18] = "pconfig",
+    [20] = "cet-ibt",
 
     [26] = "ibrsb",         [27] = "stibp",
     [28] = "l1d_flush",     [29] = "arch_caps",

xen/arch/x86/msr.c

@@ -167,6 +167,9 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
     case MSR_CORE_CAPABILITIES:
     case MSR_TSX_FORCE_ABORT:
     case MSR_TSX_CTRL:
+    case MSR_U_CET:
+    case MSR_S_CET:
+    case MSR_PL0_SSP ... MSR_INTERRUPT_SSP_TABLE:
     case MSR_AMD64_LWP_CFG:
     case MSR_AMD64_LWP_CBADDR:
     case MSR_PPIN_CTL:
@@ -324,6 +327,9 @@ int guest_wrmsr(struct vcpu *v, uint32_t msr, uint64_t val)
     case MSR_TEST_CTRL:
     case MSR_TSX_FORCE_ABORT:
     case MSR_TSX_CTRL:
+    case MSR_U_CET:
+    case MSR_S_CET:
+    case MSR_PL0_SSP ... MSR_INTERRUPT_SSP_TABLE:
     case MSR_AMD64_LWP_CFG:
     case MSR_AMD64_LWP_CBADDR:
     case MSR_PPIN_CTL:

xen/include/asm-x86/msr-index.h

@@ -66,6 +66,14 @@
 #define  TSX_CTRL_RTM_DISABLE               (_AC(1, ULL) <<  0)
 #define  TSX_CTRL_CPUID_CLEAR               (_AC(1, ULL) <<  1)
 
+#define MSR_U_CET                           0x000006a0
+#define MSR_S_CET                           0x000006a2
+#define MSR_PL0_SSP                         0x000006a4
+#define MSR_PL1_SSP                         0x000006a5
+#define MSR_PL2_SSP                         0x000006a6
+#define MSR_PL3_SSP                         0x000006a7
+#define MSR_INTERRUPT_SSP_TABLE             0x000006a8
+
 /*
  * Legacy MSR constants in need of cleanup.  No new MSRs below this comment.
  */

xen/include/public/arch-x86/cpufeatureset.h

@@ -229,6 +229,7 @@ XEN_CPUFEATURE(UMIP,          6*32+ 2) /*S  User Mode Instruction Prevention */
 XEN_CPUFEATURE(PKU,           6*32+ 3) /*H  Protection Keys for Userspace */
 XEN_CPUFEATURE(OSPKE,         6*32+ 4) /*!  OS Protection Keys Enable */
 XEN_CPUFEATURE(AVX512_VBMI2,  6*32+ 6) /*A  Additional AVX-512 Vector Byte Manipulation Instrs */
+XEN_CPUFEATURE(CET_SS,        6*32+ 7) /*   CET - Shadow Stacks */
 XEN_CPUFEATURE(GFNI,          6*32+ 8) /*A  Galois Field Instrs */
 XEN_CPUFEATURE(VAES,          6*32+ 9) /*A  Vector AES Instrs */
 XEN_CPUFEATURE(VPCLMULQDQ,    6*32+10) /*A  Vector Carry-less Multiplication Instrs */
@@ -254,6 +255,7 @@ XEN_CPUFEATURE(AVX512_4VNNIW, 9*32+ 2) /*A  AVX512 Neural Network Instructions *
 XEN_CPUFEATURE(AVX512_4FMAPS, 9*32+ 3) /*A  AVX512 Multiply Accumulation Single Precision */
 XEN_CPUFEATURE(MD_CLEAR,      9*32+10) /*A  VERW clears microarchitectural buffers */
 XEN_CPUFEATURE(TSX_FORCE_ABORT, 9*32+13) /* MSR_TSX_FORCE_ABORT.RTM_ABORT */
+XEN_CPUFEATURE(CET_IBT,       9*32+20) /*   CET - Indirect Branch Tracking */
 XEN_CPUFEATURE(IBRSB,         9*32+26) /*A  IBRS and IBPB support (used by Intel) */
 XEN_CPUFEATURE(STIBP,         9*32+27) /*A  STIBP */
 XEN_CPUFEATURE(L1D_FLUSH,     9*32+28) /*S  MSR_FLUSH_CMD and L1D flush. */