nvic: Implement AIRCR changes for v8M

The Application Interrupt and Reset Control Register has some changes
for v8M:
 * new bits SYSRESETREQS, BFHFNMINS and PRIS: these all have
   real state if the security extension is implemented and otherwise
   are constant
 * the PRIGROUP field is banked between security states
 * non-secure code can be blocked from using the SYSRESET bit
   to reset the system if SYSRESETREQS is set

Implement the new state and the changes to register read and write.
For the moment we ignore the effects of the secure PRIGROUP.
We will implement the effects of PRIS and BFHFNMIS later.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 1505240046-11454-6-git-send-email-peter.maydell@linaro.org

4 files changed, 59 insertions, 12 deletions

diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
index fa5dd23f09..d745f38361 100644
--- a/hw/intc/armv7m_nvic.c
+++ b/hw/intc/armv7m_nvic.c
@@ -129,7 +129,7 @@ static bool nvic_isrpending(NVICState *s)
  */
 static inline uint32_t nvic_gprio_mask(NVICState *s)
 {
-    return ~0U << (s->prigroup + 1);
+    return ~0U << (s->prigroup[M_REG_NS] + 1);
 }
 
 /* Recompute vectpending and exception_prio */
@@ -451,8 +451,21 @@ static uint32_t nvic_readl(NVICState *s, uint32_t offset, MemTxAttrs attrs)
         return val;
     case 0xd08: /* Vector Table Offset.  */
         return cpu->env.v7m.vecbase[attrs.secure];
-    case 0xd0c: /* Application Interrupt/Reset Control.  */
-        return 0xfa050000 | (s->prigroup << 8);
+    case 0xd0c: /* Application Interrupt/Reset Control (AIRCR) */
+        val = 0xfa050000 | (s->prigroup[attrs.secure] << 8);
+        if (attrs.secure) {
+            /* s->aircr stores PRIS, BFHFNMINS, SYSRESETREQS */
+            val |= cpu->env.v7m.aircr;
+        } else {
+            if (arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+                /* BFHFNMINS is R/O from NS; other bits are RAZ/WI. If
+                 * security isn't supported then BFHFNMINS is RAO (and
+                 * the bit in env.v7m.aircr is always set).
+                 */
+                val |= cpu->env.v7m.aircr & R_V7M_AIRCR_BFHFNMINS_MASK;
+            }
+        }
+        return val;
     case 0xd10: /* System Control.  */
         /* TODO: Implement SLEEPONEXIT.  */
         return 0;
@@ -660,22 +673,35 @@ static void nvic_writel(NVICState *s, uint32_t offset, uint32_t value,
     case 0xd08: /* Vector Table Offset.  */
         cpu->env.v7m.vecbase[attrs.secure] = value & 0xffffff80;
         break;
-    case 0xd0c: /* Application Interrupt/Reset Control.  */
-        if ((value >> 16) == 0x05fa) {
-            if (value & 4) {
-                qemu_irq_pulse(s->sysresetreq);
+    case 0xd0c: /* Application Interrupt/Reset Control (AIRCR) */
+        if ((value >> R_V7M_AIRCR_VECTKEY_SHIFT) == 0x05fa) {
+            if (value & R_V7M_AIRCR_SYSRESETREQ_MASK) {
+                if (attrs.secure ||
+                    !(cpu->env.v7m.aircr & R_V7M_AIRCR_SYSRESETREQS_MASK)) {
+                    qemu_irq_pulse(s->sysresetreq);
+                }
             }
-            if (value & 2) {
+            if (value & R_V7M_AIRCR_VECTCLRACTIVE_MASK) {
                 qemu_log_mask(LOG_GUEST_ERROR,
                               "Setting VECTCLRACTIVE when not in DEBUG mode "
                               "is UNPREDICTABLE\n");
             }
-            if (value & 1) {
+            if (value & R_V7M_AIRCR_VECTRESET_MASK) {
+                /* NB: this bit is RES0 in v8M */
                 qemu_log_mask(LOG_GUEST_ERROR,
                               "Setting VECTRESET when not in DEBUG mode "
                               "is UNPREDICTABLE\n");
             }
-            s->prigroup = extract32(value, 8, 3);
+            s->prigroup[attrs.secure] = extract32(value,
+                                                  R_V7M_AIRCR_PRIGROUP_SHIFT,
+                                                  R_V7M_AIRCR_PRIGROUP_LENGTH);
+            if (attrs.secure) {
+                /* These bits are only writable by secure */
+                cpu->env.v7m.aircr = value &
+                    (R_V7M_AIRCR_SYSRESETREQS_MASK |
+                     R_V7M_AIRCR_BFHFNMINS_MASK |
+                     R_V7M_AIRCR_PRIS_MASK);
+            }
             nvic_irq_update(s);
         }
         break;
@@ -1193,6 +1219,7 @@ static const VMStateDescription vmstate_nvic_security = {
     .fields = (VMStateField[]) {
         VMSTATE_STRUCT_ARRAY(sec_vectors, NVICState, NVIC_INTERNAL_VECTORS, 1,
                              vmstate_VecInfo, VecInfo),
+        VMSTATE_UINT32(prigroup[M_REG_S], NVICState),
         VMSTATE_END_OF_LIST()
     }
 };
@@ -1205,7 +1232,7 @@ static const VMStateDescription vmstate_nvic = {
     .fields = (VMStateField[]) {
         VMSTATE_STRUCT_ARRAY(vectors, NVICState, NVIC_MAX_VECTORS, 1,
                              vmstate_VecInfo, VecInfo),
-        VMSTATE_UINT32(prigroup, NVICState),
+        VMSTATE_UINT32(prigroup[M_REG_NS], NVICState),
         VMSTATE_END_OF_LIST()
     },
     .subsections = (const VMStateDescription*[]) {
diff --git a/include/hw/intc/armv7m_nvic.h b/include/hw/intc/armv7m_nvic.h
index 329774e82b..e96e488c77 100644
--- a/include/hw/intc/armv7m_nvic.h
+++ b/include/hw/intc/armv7m_nvic.h
@@ -55,7 +55,8 @@ typedef struct NVICState {
      * Entries in sec_vectors[] for non-banked exception numbers are unused.
      */
     VecInfo sec_vectors[NVIC_INTERNAL_VECTORS];
-    uint32_t prigroup;
+    /* The PRIGROUP field in AIRCR is banked */
+    uint32_t prigroup[M_REG_NUM_BANKS];
 
     /* The following fields are all cached state that can be recalculated
      * from the vectors[] and sec_vectors[] arrays and the prigroup field:
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 20a3445bda..33449790e5 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -187,6 +187,13 @@ static void arm_cpu_reset(CPUState *s)
 
         if (arm_feature(env, ARM_FEATURE_M_SECURITY)) {
             env->v7m.secure = true;
+        } else {
+            /* This bit resets to 0 if security is supported, but 1 if
+             * it is not. The bit is not present in v7M, but we set it
+             * here so we can avoid having to make checks on it conditional
+             * on ARM_FEATURE_V8 (we don't let the guest see the bit).
+             */
+            env->v7m.aircr = R_V7M_AIRCR_BFHFNMINS_MASK;
         }
 
         /* In v7M the reset value of this bit is IMPDEF, but ARM recommends
diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 6e50ae2b55..a52ec6b72b 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -449,6 +449,7 @@ typedef struct CPUARMState {
         int exception;
         uint32_t primask[M_REG_NUM_BANKS];
         uint32_t faultmask[M_REG_NUM_BANKS];
+        uint32_t aircr; /* only holds r/w state if security extn implemented */
         uint32_t secure; /* Is CPU in Secure state? (not guest visible) */
     } v7m;
 
@@ -1200,6 +1201,17 @@ FIELD(V7M_CCR, STKALIGN, 9, 1)
 FIELD(V7M_CCR, DC, 16, 1)
 FIELD(V7M_CCR, IC, 17, 1)
 
+/* V7M AIRCR bits */
+FIELD(V7M_AIRCR, VECTRESET, 0, 1)
+FIELD(V7M_AIRCR, VECTCLRACTIVE, 1, 1)
+FIELD(V7M_AIRCR, SYSRESETREQ, 2, 1)
+FIELD(V7M_AIRCR, SYSRESETREQS, 3, 1)
+FIELD(V7M_AIRCR, PRIGROUP, 8, 3)
+FIELD(V7M_AIRCR, BFHFNMINS, 13, 1)
+FIELD(V7M_AIRCR, PRIS, 14, 1)
+FIELD(V7M_AIRCR, ENDIANNESS, 15, 1)
+FIELD(V7M_AIRCR, VECTKEY, 16, 16)
+
 /* V7M CFSR bits for MMFSR */
 FIELD(V7M_CFSR, IACCVIOL, 0, 1)
 FIELD(V7M_CFSR, DACCVIOL, 1, 1)