target/arm: Implement new FEAT_ECV trap bits

The functionality defined by ID_AA64MMFR0_EL1.ECV == 1 is:
 * four new trap bits for various counter and timer registers
 * the CNTHCTL_EL2.EVNTIS and CNTKCTL_EL1.EVNTIS bits which control
   scaling of the event stream. This is a no-op for us, because we don't
   implement the event stream (our WFE is a NOP): all we need to do is
   allow CNTHCTL_EL2.ENVTIS to be read and written.
 * extensions to PMSCR_EL1.PCT, PMSCR_EL2.PCT, TRFCR_EL1.TS and
   TRFCR_EL2.TS: these are all no-ops for us, because we don't implement
   FEAT_SPE or FEAT_TRF.
 * new registers CNTPCTSS_EL0 and NCTVCTSS_EL0 which are
   "self-sychronizing" views of the CNTPCT_EL0 and CNTVCT_EL0, meaning
   that no barriers are needed around their accesses. For us these
   are just the same as the normal views, because all our sysregs are
   inherently self-sychronizing.

In this commit we implement the trap handling and permit the new
CNTHCTL_EL2 bits to be written.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240301183219.2424889-6-peter.maydell@linaro.org

target/arm/cpu-features.h

@@ -741,6 +741,11 @@ static inline bool isar_feature_aa64_fgt(const ARMISARegisters *id)
     return FIELD_EX64(id->id_aa64mmfr0, ID_AA64MMFR0, FGT) != 0;
 }
 
+static inline bool isar_feature_aa64_ecv_traps(const ARMISARegisters *id)
+{
+    return FIELD_EX64(id->id_aa64mmfr0, ID_AA64MMFR0, ECV) > 0;
+}
+
 static inline bool isar_feature_aa64_vh(const ARMISARegisters *id)
 {
     return FIELD_EX64(id->id_aa64mmfr1, ID_AA64MMFR1, VH) != 0;

target/arm/helper.c

@@ -2530,6 +2530,11 @@ static CPAccessResult gt_counter_access(CPUARMState *env, int timeridx,
              : !extract32(env->cp15.cnthctl_el2, 0, 1))) {
             return CP_ACCESS_TRAP_EL2;
         }
+        if (has_el2 && timeridx == GTIMER_VIRT) {
+            if (FIELD_EX64(env->cp15.cnthctl_el2, CNTHCTL, EL1TVCT)) {
+                return CP_ACCESS_TRAP_EL2;
+            }
+        }
         break;
     }
     return CP_ACCESS_OK;
@@ -2573,6 +2578,11 @@ static CPAccessResult gt_timer_access(CPUARMState *env, int timeridx,
                 }
             }
         }
+        if (has_el2 && timeridx == GTIMER_VIRT) {
+            if (FIELD_EX64(env->cp15.cnthctl_el2, CNTHCTL, EL1TVT)) {
+                return CP_ACCESS_TRAP_EL2;
+            }
+        }
         break;
     }
     return CP_ACCESS_OK;
@@ -2982,6 +2992,14 @@ static void gt_cnthctl_write(CPUARMState *env, const ARMCPRegInfo *ri,
     if (cpu_isar_feature(aa64_rme, cpu)) {
         valid_mask |= R_CNTHCTL_CNTVMASK_MASK | R_CNTHCTL_CNTPMASK_MASK;
     }
+    if (cpu_isar_feature(aa64_ecv_traps, cpu)) {
+        valid_mask |=
+            R_CNTHCTL_EL1TVT_MASK |
+            R_CNTHCTL_EL1TVCT_MASK |
+            R_CNTHCTL_EL1NVPCT_MASK |
+            R_CNTHCTL_EL1NVVCT_MASK |
+            R_CNTHCTL_EVNTIS_MASK;
+    }
 
     /* Clear RES0 bits */
     value &= valid_mask;
@@ -6564,7 +6582,6 @@ static CPAccessResult e2h_access(CPUARMState *env, const ARMCPRegInfo *ri,
 {
     if (arm_current_el(env) == 1) {
         /* This must be a FEAT_NV access */
-        /* TODO: FEAT_ECV will need to check CNTHCTL_EL2 here */
         return CP_ACCESS_OK;
     }
     if (!(arm_hcr_el2_eff(env) & HCR_E2H)) {
@@ -6573,6 +6590,30 @@ static CPAccessResult e2h_access(CPUARMState *env, const ARMCPRegInfo *ri,
     return CP_ACCESS_OK;
 }
 
+static CPAccessResult access_el1nvpct(CPUARMState *env, const ARMCPRegInfo *ri,
+                                      bool isread)
+{
+    if (arm_current_el(env) == 1) {
+        /* This must be a FEAT_NV access with NVx == 101 */
+        if (FIELD_EX64(env->cp15.cnthctl_el2, CNTHCTL, EL1NVPCT)) {
+            return CP_ACCESS_TRAP_EL2;
+        }
+    }
+    return e2h_access(env, ri, isread);
+}
+
+static CPAccessResult access_el1nvvct(CPUARMState *env, const ARMCPRegInfo *ri,
+                                      bool isread)
+{
+    if (arm_current_el(env) == 1) {
+        /* This must be a FEAT_NV access with NVx == 101 */
+        if (FIELD_EX64(env->cp15.cnthctl_el2, CNTHCTL, EL1NVVCT)) {
+            return CP_ACCESS_TRAP_EL2;
+        }
+    }
+    return e2h_access(env, ri, isread);
+}
+
 /* Test if system register redirection is to occur in the current state.  */
 static bool redirect_for_e2h(CPUARMState *env)
 {
@@ -8398,14 +8439,14 @@ static const ARMCPRegInfo vhe_reginfo[] = {
     { .name = "CNTP_CTL_EL02", .state = ARM_CP_STATE_AA64,
       .opc0 = 3, .opc1 = 5, .crn = 14, .crm = 2, .opc2 = 1,
       .type = ARM_CP_IO | ARM_CP_ALIAS,
-      .access = PL2_RW, .accessfn = e2h_access,
+      .access = PL2_RW, .accessfn = access_el1nvpct,
       .nv2_redirect_offset = 0x180 | NV2_REDIR_NO_NV1,
       .fieldoffset = offsetof(CPUARMState, cp15.c14_timer[GTIMER_PHYS].ctl),
       .writefn = gt_phys_ctl_write, .raw_writefn = raw_write },
     { .name = "CNTV_CTL_EL02", .state = ARM_CP_STATE_AA64,
       .opc0 = 3, .opc1 = 5, .crn = 14, .crm = 3, .opc2 = 1,
       .type = ARM_CP_IO | ARM_CP_ALIAS,
-      .access = PL2_RW, .accessfn = e2h_access,
+      .access = PL2_RW, .accessfn = access_el1nvvct,
       .nv2_redirect_offset = 0x170 | NV2_REDIR_NO_NV1,
       .fieldoffset = offsetof(CPUARMState, cp15.c14_timer[GTIMER_VIRT].ctl),
       .writefn = gt_virt_ctl_write, .raw_writefn = raw_write },
@@ -8424,14 +8465,14 @@ static const ARMCPRegInfo vhe_reginfo[] = {
       .type = ARM_CP_IO | ARM_CP_ALIAS,
       .fieldoffset = offsetof(CPUARMState, cp15.c14_timer[GTIMER_PHYS].cval),
       .nv2_redirect_offset = 0x178 | NV2_REDIR_NO_NV1,
-      .access = PL2_RW, .accessfn = e2h_access,
+      .access = PL2_RW, .accessfn = access_el1nvpct,
       .writefn = gt_phys_cval_write, .raw_writefn = raw_write },
     { .name = "CNTV_CVAL_EL02", .state = ARM_CP_STATE_AA64,
       .opc0 = 3, .opc1 = 5, .crn = 14, .crm = 3, .opc2 = 2,
       .type = ARM_CP_IO | ARM_CP_ALIAS,
       .nv2_redirect_offset = 0x168 | NV2_REDIR_NO_NV1,
       .fieldoffset = offsetof(CPUARMState, cp15.c14_timer[GTIMER_VIRT].cval),
-      .access = PL2_RW, .accessfn = e2h_access,
+      .access = PL2_RW, .accessfn = access_el1nvvct,
       .writefn = gt_virt_cval_write, .raw_writefn = raw_write },
 #endif
 };