target/arm: Add support for FEAT_SSBS, Speculative Store Bypass Safe

Add support for FEAT_SSBS. SSBS (Speculative Store Bypass Safe) is an
optional feature in ARMv8.0, and mandatory in ARMv8.5.

Signed-off-by: Rebecca Cran <rebecca@nuviainc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210216224543.16142-2-rebecca@nuviainc.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/cpu.h

@@ -1206,6 +1206,7 @@ void pmu_init(ARMCPU *cpu);
 #define SCTLR_TE      (1U << 30) /* AArch32 only */
 #define SCTLR_EnIB    (1U << 30) /* v8.3, AArch64 only */
 #define SCTLR_EnIA    (1U << 31) /* v8.3, AArch64 only */
+#define SCTLR_DSSBS_32 (1U << 31) /* v8.5, AArch32 only */
 #define SCTLR_BT0     (1ULL << 35) /* v8.5-BTI */
 #define SCTLR_BT1     (1ULL << 36) /* v8.5-BTI */
 #define SCTLR_ITFSB   (1ULL << 37) /* v8.5-MemTag */
@@ -1213,7 +1214,7 @@ void pmu_init(ARMCPU *cpu);
 #define SCTLR_TCF     (3ULL << 40) /* v8.5-MemTag */
 #define SCTLR_ATA0    (1ULL << 42) /* v8.5-MemTag */
 #define SCTLR_ATA     (1ULL << 43) /* v8.5-MemTag */
-#define SCTLR_DSSBS   (1ULL << 44) /* v8.5 */
+#define SCTLR_DSSBS_64 (1ULL << 44) /* v8.5, AArch64 only */
 
 #define CPTR_TCPAC    (1U << 31)
 #define CPTR_TTA      (1U << 20)
@@ -1250,6 +1251,7 @@ void pmu_init(ARMCPU *cpu);
 #define CPSR_IL (1U << 20)
 #define CPSR_DIT (1U << 21)
 #define CPSR_PAN (1U << 22)
+#define CPSR_SSBS (1U << 23)
 #define CPSR_J (1U << 24)
 #define CPSR_IT_0_1 (3U << 25)
 #define CPSR_Q (1U << 27)
@@ -1312,6 +1314,7 @@ void pmu_init(ARMCPU *cpu);
 #define PSTATE_A (1U << 8)
 #define PSTATE_D (1U << 9)
 #define PSTATE_BTYPE (3U << 10)
+#define PSTATE_SSBS (1U << 12)
 #define PSTATE_IL (1U << 20)
 #define PSTATE_SS (1U << 21)
 #define PSTATE_PAN (1U << 22)
@@ -3915,6 +3918,11 @@ static inline bool isar_feature_aa32_dit(const ARMISARegisters *id)
     return FIELD_EX32(id->id_pfr0, ID_PFR0, DIT) != 0;
 }
 
+static inline bool isar_feature_aa32_ssbs(const ARMISARegisters *id)
+{
+    return FIELD_EX32(id->id_pfr2, ID_PFR2, SSBS) != 0;
+}
+
 /*
  * 64-bit feature tests via id registers.
  */
@@ -4169,6 +4177,11 @@ static inline bool isar_feature_aa64_dit(const ARMISARegisters *id)
     return FIELD_EX64(id->id_aa64pfr0, ID_AA64PFR0, DIT) != 0;
 }
 
+static inline bool isar_feature_aa64_ssbs(const ARMISARegisters *id)
+{
+    return FIELD_EX64(id->id_aa64pfr1, ID_AA64PFR1, SSBS) != 0;
+}
+
 /*
  * Feature tests for "does this exist in either 32-bit or 64-bit?"
  */

target/arm/helper.c

@@ -4450,6 +4450,24 @@ static const ARMCPRegInfo dit_reginfo = {
     .readfn = aa64_dit_read, .writefn = aa64_dit_write
 };
 
+static uint64_t aa64_ssbs_read(CPUARMState *env, const ARMCPRegInfo *ri)
+{
+    return env->pstate & PSTATE_SSBS;
+}
+
+static void aa64_ssbs_write(CPUARMState *env, const ARMCPRegInfo *ri,
+                           uint64_t value)
+{
+    env->pstate = (env->pstate & ~PSTATE_SSBS) | (value & PSTATE_SSBS);
+}
+
+static const ARMCPRegInfo ssbs_reginfo = {
+    .name = "SSBS", .state = ARM_CP_STATE_AA64,
+    .opc0 = 3, .opc1 = 3, .crn = 4, .crm = 2, .opc2 = 6,
+    .type = ARM_CP_NO_RAW, .access = PL0_RW,
+    .readfn = aa64_ssbs_read, .writefn = aa64_ssbs_write
+};
+
 static CPAccessResult aa64_cacheop_poc_access(CPUARMState *env,
                                               const ARMCPRegInfo *ri,
                                               bool isread)
@@ -8244,6 +8262,9 @@ void register_cp_regs_for_features(ARMCPU *cpu)
     if (cpu_isar_feature(aa64_dit, cpu)) {
         define_one_arm_cp_reg(cpu, &dit_reginfo);
     }
+    if (cpu_isar_feature(aa64_ssbs, cpu)) {
+        define_one_arm_cp_reg(cpu, &ssbs_reginfo);
+    }
 
     if (arm_feature(env, ARM_FEATURE_EL2) && cpu_isar_feature(aa64_vh, cpu)) {
         define_arm_cp_regs(cpu, vhe_reginfo);
@@ -9463,6 +9484,14 @@ static void take_aarch32_exception(CPUARMState *env, int new_mode,
     env->uncached_cpsr &= ~(CPSR_IL | CPSR_J);
     env->daif |= mask;
 
+    if (cpu_isar_feature(aa32_ssbs, env_archcpu(env))) {
+        if (env->cp15.sctlr_el[new_el] & SCTLR_DSSBS_32) {
+            env->uncached_cpsr |= CPSR_SSBS;
+        } else {
+            env->uncached_cpsr &= ~CPSR_SSBS;
+        }
+    }
+
     if (new_mode == ARM_CPU_MODE_HYP) {
         env->thumb = (env->cp15.sctlr_el[2] & SCTLR_TE) != 0;
         env->elr_el[2] = env->regs[15];
@@ -9973,6 +10002,14 @@ static void arm_cpu_do_interrupt_aarch64(CPUState *cs)
         new_mode |= PSTATE_TCO;
     }
 
+    if (cpu_isar_feature(aa64_ssbs, cpu)) {
+        if (env->cp15.sctlr_el[new_el] & SCTLR_DSSBS_64) {
+            new_mode |= PSTATE_SSBS;
+        } else {
+            new_mode &= ~PSTATE_SSBS;
+        }
+    }
+
     pstate_write(env, PSTATE_DAIF | new_mode);
     env->aarch64 = 1;
     aarch64_restore_sp(env, new_el);

target/arm/internals.h

@@ -987,6 +987,9 @@ static inline uint32_t aarch32_cpsr_valid_mask(uint64_t features,
     if (isar_feature_aa32_dit(id)) {
         valid |= CPSR_DIT;
     }
+    if (isar_feature_aa32_ssbs(id)) {
+        valid |= CPSR_SSBS;
+    }
 
     return valid;
 }
@@ -1008,6 +1011,9 @@ static inline uint32_t aarch64_pstate_valid_mask(const ARMISARegisters *id)
     if (isar_feature_aa64_dit(id)) {
         valid |= PSTATE_DIT;
     }
+    if (isar_feature_aa64_ssbs(id)) {
+        valid |= PSTATE_SSBS;
+    }
     if (isar_feature_aa64_mte(id)) {
         valid |= PSTATE_TCO;
     }

target/arm/translate-a64.c

@@ -1703,6 +1703,18 @@ static void handle_msr_i(DisasContext *s, uint32_t insn,
         tcg_temp_free_i32(t1);
         break;
 
+    case 0x19: /* SSBS */
+        if (!dc_isar_feature(aa64_ssbs, s)) {
+            goto do_unallocated;
+        }
+        if (crm & 1) {
+            set_pstate_bits(PSTATE_SSBS);
+        } else {
+            clear_pstate_bits(PSTATE_SSBS);
+        }
+        /* Don't need to rebuild hflags since SSBS is a nop */
+        break;
+
     case 0x1a: /* DIT */
         if (!dc_isar_feature(aa64_dit, s)) {
             goto do_unallocated;