[Qemu-devel] [PATCH 2/2] target/arm: Take exceptions on ATS instructions when needed

[Peter Maydell <peter.maydell@linaro.org>]

The translation table walk for an ATS instruction can result in
various faults.  In general these are just reported back via the
PAR_EL1 fault status fields, but in some cases the architecture
requires that the fault is turned into an exception:
 * synchronous stage 2 faults of any kind during AT S1E0* and
   AT S1E1* instructions executed from NS EL1 fault to EL2 or EL3
 * synchronous external aborts are taken as Data Abort exceptions

(This is documented in the v8A Arm ARM DDI0487A.e D5.2.11 and
G5.13.4.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 107 +++++++++++++++++++++++++++++++++++++-------
 1 file changed, 92 insertions(+), 15 deletions(-)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index b74c23a9bc0..7d82195c960 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -2944,6 +2944,73 @@ static uint64_t do_ats_write(CPUARMState *env, uint64_t value,
     ret = get_phys_addr(env, value, access_type, mmu_idx, &phys_addr, &attrs,
                         &prot, &page_size, &fi, &cacheattrs);
 
+    if (ret) {
+        /*
+         * Some kinds of translation fault must cause exceptions rather
+         * than being reported in the PAR.
+         */
+        int current_el = arm_current_el(env);
+        int target_el;
+        uint32_t syn, fsr, fsc;
+        bool take_exc = false;
+
+        if (fi.s1ptw && current_el == 1 && !arm_is_secure(env)
+            && (mmu_idx == ARMMMUIdx_S1NSE1 || mmu_idx == ARMMMUIdx_S1NSE0)) {
+            /*
+             * Synchronous stage 2 fault on an access made as part of the
+             * translation table walk for AT S1E0* or AT S1E1* insn
+             * executed from NS EL1. If this is a synchronous external abort
+             * and SCR_EL3.EA == 1, then we take a synchronous external abort
+             * to EL3. Otherwise the fault is taken as an exception to EL2,
+             * and HPFAR_EL2 holds the faulting IPA.
+             */
+            if (fi.type == ARMFault_SyncExternalOnWalk &&
+                (env->cp15.scr_el3 & SCR_EA)) {
+                target_el = 3;
+            } else {
+                env->cp15.hpfar_el2 = extract64(fi.s2addr, 12, 47) << 4;
+                target_el = 2;
+            }
+            take_exc = true;
+        } else if (fi.type == ARMFault_SyncExternalOnWalk) {
+            /*
+             * Synchronous external aborts during a translation table walk
+             * are taken as Data Abort exceptions.
+             */
+            if (fi.stage2) {
+                if (current_el == 3) {
+                    target_el = 3;
+                } else {
+                    target_el = 2;
+                }
+            } else {
+                target_el = exception_target_el(env);
+            }
+            take_exc = true;
+        }
+
+        if (take_exc) {
+            /* Construct FSR and FSC using same logic as arm_deliver_fault() */
+            if (target_el == 2 || arm_el_is_aa64(env, target_el) ||
+                arm_s1_regime_using_lpae_format(env, mmu_idx)) {
+                fsr = arm_fi_to_lfsc(&fi);
+                fsc = extract32(fsr, 0, 6);
+            } else {
+                fsr = arm_fi_to_sfsc(&fi);
+                fsc = 0x3f;
+            }
+            /*
+             * Report exception with ESR indicating a fault due to a
+             * translation table walk for a cache maintenance instruction.
+             */
+            syn = syn_data_abort_no_iss(current_el == target_el,
+                                        fi.ea, 1, fi.s1ptw, 1, fsc);
+            env->exception.vaddress = value;
+            env->exception.fsr = fsr;
+            raise_exception(env, EXCP_DATA_ABORT, syn, target_el);
+        }
+    }
+
     if (is_a64(env)) {
         format64 = true;
     } else if (arm_feature(env, ARM_FEATURE_LPAE)) {
@@ -3148,7 +3215,7 @@ static const ARMCPRegInfo vapa_cp_reginfo[] = {
     /* This underdecoding is safe because the reginfo is NO_RAW. */
     { .name = "ATS", .cp = 15, .crn = 7, .crm = 8, .opc1 = 0, .opc2 = CP_ANY,
       .access = PL1_W, .accessfn = ats_access,
-      .writefn = ats_write, .type = ARM_CP_NO_RAW },
+      .writefn = ats_write, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC },
 #endif
     REGINFO_SENTINEL
 };
@@ -4281,35 +4348,45 @@ static const ARMCPRegInfo v8_cp_reginfo[] = {
     /* 64 bit address translation operations */
     { .name = "AT_S1E1R", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 0, .crn = 7, .crm = 8, .opc2 = 0,
-      .access = PL1_W, .type = ARM_CP_NO_RAW, .writefn = ats_write64 },
+      .access = PL1_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
+      .writefn = ats_write64 },
     { .name = "AT_S1E1W", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 0, .crn = 7, .crm = 8, .opc2 = 1,
-      .access = PL1_W, .type = ARM_CP_NO_RAW, .writefn = ats_write64 },
+      .access = PL1_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
+      .writefn = ats_write64 },
     { .name = "AT_S1E0R", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 0, .crn = 7, .crm = 8, .opc2 = 2,
-      .access = PL1_W, .type = ARM_CP_NO_RAW, .writefn = ats_write64 },
+      .access = PL1_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
+      .writefn = ats_write64 },
     { .name = "AT_S1E0W", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 0, .crn = 7, .crm = 8, .opc2 = 3,
-      .access = PL1_W, .type = ARM_CP_NO_RAW, .writefn = ats_write64 },
+      .access = PL1_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
+      .writefn = ats_write64 },
     { .name = "AT_S12E1R", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 4, .crn = 7, .crm = 8, .opc2 = 4,
-      .access = PL2_W, .type = ARM_CP_NO_RAW, .writefn = ats_write64 },
+      .access = PL2_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
+      .writefn = ats_write64 },
     { .name = "AT_S12E1W", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 4, .crn = 7, .crm = 8, .opc2 = 5,
-      .access = PL2_W, .type = ARM_CP_NO_RAW, .writefn = ats_write64 },
+      .access = PL2_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
+      .writefn = ats_write64 },
     { .name = "AT_S12E0R", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 4, .crn = 7, .crm = 8, .opc2 = 6,
-      .access = PL2_W, .type = ARM_CP_NO_RAW, .writefn = ats_write64 },
+      .access = PL2_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
+      .writefn = ats_write64 },
     { .name = "AT_S12E0W", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 4, .crn = 7, .crm = 8, .opc2 = 7,
-      .access = PL2_W, .type = ARM_CP_NO_RAW, .writefn = ats_write64 },
+      .access = PL2_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
+      .writefn = ats_write64 },
     /* AT S1E2* are elsewhere as they UNDEF from EL3 if EL2 is not present */
     { .name = "AT_S1E3R", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 6, .crn = 7, .crm = 8, .opc2 = 0,
-      .access = PL3_W, .type = ARM_CP_NO_RAW, .writefn = ats_write64 },
+      .access = PL3_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
+      .writefn = ats_write64 },
     { .name = "AT_S1E3W", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 6, .crn = 7, .crm = 8, .opc2 = 1,
-      .access = PL3_W, .type = ARM_CP_NO_RAW, .writefn = ats_write64 },
+      .access = PL3_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
+      .writefn = ats_write64 },
     { .name = "PAR_EL1", .state = ARM_CP_STATE_AA64,
       .type = ARM_CP_ALIAS,
       .opc0 = 3, .opc1 = 0, .crn = 7, .crm = 4, .opc2 = 0,
@@ -4891,11 +4968,11 @@ static const ARMCPRegInfo el2_cp_reginfo[] = {
     { .name = "AT_S1E2R", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 4, .crn = 7, .crm = 8, .opc2 = 0,
       .access = PL2_W, .accessfn = at_s1e2_access,
-      .type = ARM_CP_NO_RAW, .writefn = ats_write64 },
+      .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC, .writefn = ats_write64 },
     { .name = "AT_S1E2W", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 4, .crn = 7, .crm = 8, .opc2 = 1,
       .access = PL2_W, .accessfn = at_s1e2_access,
-      .type = ARM_CP_NO_RAW, .writefn = ats_write64 },
+      .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC, .writefn = ats_write64 },
     /* The AArch32 ATS1H* operations are CONSTRAINED UNPREDICTABLE
      * if EL2 is not implemented; we choose to UNDEF. Behaviour at EL3
      * with SCR.NS == 0 outside Monitor mode is UNPREDICTABLE; we choose
@@ -4903,10 +4980,10 @@ static const ARMCPRegInfo el2_cp_reginfo[] = {
      */
     { .name = "ATS1HR", .cp = 15, .opc1 = 4, .crn = 7, .crm = 8, .opc2 = 0,
       .access = PL2_W,
-      .writefn = ats1h_write, .type = ARM_CP_NO_RAW },
+      .writefn = ats1h_write, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC },
     { .name = "ATS1HW", .cp = 15, .opc1 = 4, .crn = 7, .crm = 8, .opc2 = 1,
       .access = PL2_W,
-      .writefn = ats1h_write, .type = ARM_CP_NO_RAW },
+      .writefn = ats1h_write, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC },
     { .name = "CNTHCTL_EL2", .state = ARM_CP_STATE_BOTH,
       .opc0 = 3, .opc1 = 4, .crn = 14, .crm = 1, .opc2 = 0,
       /* ARMv7 requires bit 0 and 1 to reset to 1. ARMv8 defines the
-- 
2.20.1