target-arm: kvm64 fix save/restore of SPSR regs

The current code was negatively indexing the cpu state array and not
synchronizing banked spsr register state with the current mode's spsr
state, causing occasional failures with migration.

Some munging is done to take care of the aarch64 mapping and also to
ensure the most current value of the spsr is updated to the banked
registers (relevant for KVM<->TCG migration).
Signed-off-by: NAlex Bennée <alex.bennee@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target-arm/kvm64.c

@@ -140,6 +140,7 @@ int kvm_arch_put_registers(CPUState *cs, int level)
     uint64_t val;
     int i;
     int ret;
+    unsigned int el;
 
     ARMCPU *cpu = ARM_CPU(cs);
     CPUARMState *env = &cpu->env;
@@ -206,9 +207,22 @@ int kvm_arch_put_registers(CPUState *cs, int level)
         return ret;
     }
 
+    /* Saved Program State Registers
+     *
+     * Before we restore from the banked_spsr[] array we need to
+     * ensure that any modifications to env->spsr are correctly
+     * reflected in the banks.
+     */
+    el = arm_current_el(env);
+    if (el > 0 && !is_a64(env)) {
+        i = bank_number(env->uncached_cpsr & CPSR_M);
+        env->banked_spsr[i] = env->spsr;
+    }
+
+    /* KVM 0-4 map to QEMU banks 1-5 */
     for (i = 0; i < KVM_NR_SPSR; i++) {
         reg.id = AARCH64_CORE_REG(spsr[i]);
-        reg.addr = (uintptr_t) &env->banked_spsr[i - 1];
+        reg.addr = (uintptr_t) &env->banked_spsr[i + 1];
         ret = kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, &reg);
         if (ret) {
             return ret;
@@ -265,6 +279,7 @@ int kvm_arch_get_registers(CPUState *cs)
     struct kvm_one_reg reg;
     uint64_t val;
     uint32_t fpr;
+    unsigned int el;
     int i;
     int ret;
 
@@ -337,15 +352,25 @@ int kvm_arch_get_registers(CPUState *cs)
         return ret;
     }
 
+    /* Fetch the SPSR registers
+     *
+     * KVM SPSRs 0-4 map to QEMU banks 1-5
+     */
     for (i = 0; i < KVM_NR_SPSR; i++) {
         reg.id = AARCH64_CORE_REG(spsr[i]);
-        reg.addr = (uintptr_t) &env->banked_spsr[i - 1];
+        reg.addr = (uintptr_t) &env->banked_spsr[i + 1];
         ret = kvm_vcpu_ioctl(cs, KVM_GET_ONE_REG, &reg);
         if (ret) {
             return ret;
         }
     }
 
+    el = arm_current_el(env);
+    if (el > 0 && !is_a64(env)) {
+        i = bank_number(env->uncached_cpsr & CPSR_M);
+        env->spsr = env->banked_spsr[i];
+    }
+
     /* Advanced SIMD and FP registers
      * We map Qn = regs[2n+1]:regs[2n]
      */