[v5,5/6] target-arm: kvm64 fix save/restore of SPSR regs

Commit Message

Alex Bennée March 23, 2015, 5:05 p.m. UTC

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: Alex Bennée <[e-mail]>

---
v2 (ajb)
  - minor tweaks and clarifications
v3
  - Use the correct bank index function for setting/getting env->spsr
  - only deal with spsrs in elevated exception levels
v4
 - try and make commentary clearer
 - ensure env->banked_spsr[0] = env->spsr before we sync
v5
 - fix banking index now banking fixed
 - keep wide spacing on [ ] forms
 - claimed authorship

Comments

Peter Maydell March 26, 2015, 5:25 p.m. UTC | #1

On 23 March 2015 at 17:05, Alex Bennée <[e-mail]> wrote:
> 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: Alex Bennée <[e-mail]>
>
> ---
> v2 (ajb)
>   - minor tweaks and clarifications
> v3
>   - Use the correct bank index function for setting/getting env->spsr
>   - only deal with spsrs in elevated exception levels
> v4
>  - try and make commentary clearer
>  - ensure env->banked_spsr[0] = env->spsr before we sync
> v5
>  - fix banking index now banking fixed
>  - keep wide spacing on [ ] forms
>  - claimed authorship
>
> diff --git a/target-arm/kvm64.c b/target-arm/kvm64.c
> index 857e970..5270fa7 100644
> --- a/target-arm/kvm64.c
> +++ b/target-arm/kvm64.c
> @@ -139,6 +139,7 @@ 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;
> @@ -205,9 +206,24 @@ 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) {
> +        i = is_a64(env) ?
> +            aarch64_banked_spsr_index(el) :
> +            bank_number(env->uncached_cpsr & CPSR_M);
> +        env->banked_spsr[i] = env->spsr;

This doesn't look right. If we're currently A64 then
env->spsr is unused and this code will trash one of
the banked_spsr[] fields.

> +    }
> +
> +    /* 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;
> @@ -253,11 +269,13 @@ int kvm_arch_put_registers(CPUState *cs, int level)
>      return ret;
>  }
>
> +

Stray extra space.

-- PMM

Patch

diff --git a/target-arm/kvm64.c b/target-arm/kvm64.c
index 857e970..5270fa7 100644
--- a/target-arm/kvm64.c
+++ b/target-arm/kvm64.c
@@ -139,6 +139,7 @@  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;
@@ -205,9 +206,24 @@  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) {
+        i = is_a64(env) ?
+            aarch64_banked_spsr_index(el) :
+            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;
@@ -253,11 +269,13 @@  int kvm_arch_put_registers(CPUState *cs, int level)
     return ret;
 }
 
+
 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;
 
@@ -330,15 +348,27 @@  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) {
+        i = is_a64(env) ?
+            aarch64_banked_spsr_index(el) :
+            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]
      */