target/arm: Implement virtual SError exceptions

Virtual SError exceptions are raised by setting HCR_EL2.VSE,
and are routed to EL1 just like other virtual exceptions.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220506180242.216785-16-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/cpu.c

@@ -85,7 +85,7 @@ static bool arm_cpu_has_work(CPUState *cs)
     return (cpu->power_state != PSCI_OFF)
         && cs->interrupt_request &
         (CPU_INTERRUPT_FIQ | CPU_INTERRUPT_HARD
-         | CPU_INTERRUPT_VFIQ | CPU_INTERRUPT_VIRQ
+         | CPU_INTERRUPT_VFIQ | CPU_INTERRUPT_VIRQ | CPU_INTERRUPT_VSERR
          | CPU_INTERRUPT_EXITTB);
 }
 
@@ -511,6 +511,12 @@ static inline bool arm_excp_unmasked(CPUState *cs, unsigned int excp_idx,
             return false;
         }
         return !(env->daif & PSTATE_I);
+    case EXCP_VSERR:
+        if (!(hcr_el2 & HCR_AMO) || (hcr_el2 & HCR_TGE)) {
+            /* VIRQs are only taken when hypervized.  */
+            return false;
+        }
+        return !(env->daif & PSTATE_A);
     default:
         g_assert_not_reached();
     }
@@ -632,6 +638,17 @@ static bool arm_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
             goto found;
         }
     }
+    if (interrupt_request & CPU_INTERRUPT_VSERR) {
+        excp_idx = EXCP_VSERR;
+        target_el = 1;
+        if (arm_excp_unmasked(cs, excp_idx, target_el,
+                              cur_el, secure, hcr_el2)) {
+            /* Taking a virtual abort clears HCR_EL2.VSE */
+            env->cp15.hcr_el2 &= ~HCR_VSE;
+            cpu_reset_interrupt(cs, CPU_INTERRUPT_VSERR);
+            goto found;
+        }
+    }
     return false;
 
  found:
@@ -684,6 +701,25 @@ void arm_cpu_update_vfiq(ARMCPU *cpu)
     }
 }
 
+void arm_cpu_update_vserr(ARMCPU *cpu)
+{
+    /*
+     * Update the interrupt level for VSERR, which is the HCR_EL2.VSE bit.
+     */
+    CPUARMState *env = &cpu->env;
+    CPUState *cs = CPU(cpu);
+
+    bool new_state = env->cp15.hcr_el2 & HCR_VSE;
+
+    if (new_state != ((cs->interrupt_request & CPU_INTERRUPT_VSERR) != 0)) {
+        if (new_state) {
+            cpu_interrupt(cs, CPU_INTERRUPT_VSERR);
+        } else {
+            cpu_reset_interrupt(cs, CPU_INTERRUPT_VSERR);
+        }
+    }
+}
+
 #ifndef CONFIG_USER_ONLY
 static void arm_cpu_set_irq(void *opaque, int irq, int level)
 {

target/arm/cpu.h

@@ -56,6 +56,7 @@
 #define EXCP_LSERR          21   /* v8M LSERR SecureFault */
 #define EXCP_UNALIGNED      22   /* v7M UNALIGNED UsageFault */
 #define EXCP_DIVBYZERO      23   /* v7M DIVBYZERO UsageFault */
+#define EXCP_VSERR          24
 /* NB: add new EXCP_ defines to the array in arm_log_exception() too */
 
 #define ARMV7M_EXCP_RESET   1
@@ -89,6 +90,7 @@ enum {
 #define CPU_INTERRUPT_FIQ   CPU_INTERRUPT_TGT_EXT_1
 #define CPU_INTERRUPT_VIRQ  CPU_INTERRUPT_TGT_EXT_2
 #define CPU_INTERRUPT_VFIQ  CPU_INTERRUPT_TGT_EXT_3
+#define CPU_INTERRUPT_VSERR CPU_INTERRUPT_TGT_INT_0
 
 /* The usual mapping for an AArch64 system register to its AArch32
  * counterpart is for the 32 bit world to have access to the lower

target/arm/helper.c

@@ -1863,7 +1863,12 @@ static uint64_t isr_read(CPUARMState *env, const ARMCPRegInfo *ri)
         }
     }
 
-    /* External aborts are not possible in QEMU so A bit is always clear */
+    if (hcr_el2 & HCR_AMO) {
+        if (cs->interrupt_request & CPU_INTERRUPT_VSERR) {
+            ret |= CPSR_A;
+        }
+    }
+
     return ret;
 }
 
@@ -5175,6 +5180,7 @@ static void do_hcr_write(CPUARMState *env, uint64_t value, uint64_t valid_mask)
     g_assert(qemu_mutex_iothread_locked());
     arm_cpu_update_virq(cpu);
     arm_cpu_update_vfiq(cpu);
+    arm_cpu_update_vserr(cpu);
 }
 
 static void hcr_write(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t value)
@@ -9331,6 +9337,7 @@ void arm_log_exception(CPUState *cs)
             [EXCP_LSERR] = "v8M LSERR UsageFault",
             [EXCP_UNALIGNED] = "v7M UNALIGNED UsageFault",
             [EXCP_DIVBYZERO] = "v7M DIVBYZERO UsageFault",
+            [EXCP_VSERR] = "Virtual SERR",
         };
 
         if (idx >= 0 && idx < ARRAY_SIZE(excnames)) {
@@ -9843,6 +9850,31 @@ static void arm_cpu_do_interrupt_aarch32(CPUState *cs)
         mask = CPSR_A | CPSR_I | CPSR_F;
         offset = 4;
         break;
+    case EXCP_VSERR:
+        {
+            /*
+             * Note that this is reported as a data abort, but the DFAR
+             * has an UNKNOWN value.  Construct the SError syndrome from
+             * AET and ExT fields.
+             */
+            ARMMMUFaultInfo fi = { .type = ARMFault_AsyncExternal, };
+
+            if (extended_addresses_enabled(env)) {
+                env->exception.fsr = arm_fi_to_lfsc(&fi);
+            } else {
+                env->exception.fsr = arm_fi_to_sfsc(&fi);
+            }
+            env->exception.fsr |= env->cp15.vsesr_el2 & 0xd000;
+            A32_BANKED_CURRENT_REG_SET(env, dfsr, env->exception.fsr);
+            qemu_log_mask(CPU_LOG_INT, "...with IFSR 0x%x\n",
+                          env->exception.fsr);
+
+            new_mode = ARM_CPU_MODE_ABT;
+            addr = 0x10;
+            mask = CPSR_A | CPSR_I;
+            offset = 8;
+        }
+        break;
     case EXCP_SMC:
         new_mode = ARM_CPU_MODE_MON;
         addr = 0x08;
@@ -10063,6 +10095,12 @@ static void arm_cpu_do_interrupt_aarch64(CPUState *cs)
     case EXCP_VFIQ:
         addr += 0x100;
         break;
+    case EXCP_VSERR:
+        addr += 0x180;
+        /* Construct the SError syndrome from IDS and ISS fields. */
+        env->exception.syndrome = syn_serror(env->cp15.vsesr_el2 & 0x1ffffff);
+        env->cp15.esr_el[new_el] = env->exception.syndrome;
+        break;
     default:
         cpu_abort(cs, "Unhandled exception 0x%x\n", cs->exception_index);
     }

target/arm/internals.h

@@ -947,6 +947,14 @@ void arm_cpu_update_virq(ARMCPU *cpu);
  */
 void arm_cpu_update_vfiq(ARMCPU *cpu);
 
+/**
+ * arm_cpu_update_vserr: Update CPU_INTERRUPT_VSERR bit
+ *
+ * Update the CPU_INTERRUPT_VSERR bit in cs->interrupt_request,
+ * following a change to the HCR_EL2.VSE bit.
+ */
+void arm_cpu_update_vserr(ARMCPU *cpu);
+
 /**
  * arm_mmu_idx_el:
  * @env: The cpu environment

target/arm/syndrome.h

@@ -287,4 +287,9 @@ static inline uint32_t syn_pcalignment(void)
     return (EC_PCALIGNMENT << ARM_EL_EC_SHIFT) | ARM_EL_IL;
 }
 
+static inline uint32_t syn_serror(uint32_t extra)
+{
+    return (EC_SERROR << ARM_EL_EC_SHIFT) | ARM_EL_IL | extra;
+}
+
 #endif /* TARGET_ARM_SYNDROME_H */