Re: [PATCH 09/10] armv7m: FAULTMASK should be 0 on reset

["Alex Bennée" <alex.bennee@linaro.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> From: Michael Davidsaver <mdavidsaver@gmail.com>
>
> For M profile CPUs, FAULTMASK should be 0 on reset, like PRIMASK.
> QEMU stores FAULTMASK in the PSTATE F bit, so (as with PRIMASK in the
> I bit) we have to clear these to undo the A profile default of 1.
>
> Update the comment accordingly and move it so that it's closer to the
> code it's referring to.
>
> Signed-off-by: Michael Davidsaver <mdavidsaver@gmail.com>
> [PMM: rewrote commit message, moved comments]
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

> ---
>  target/arm/cpu.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/target/arm/cpu.c b/target/arm/cpu.c
> index c804f59..0814f73 100644
> --- a/target/arm/cpu.c
> +++ b/target/arm/cpu.c
> @@ -179,15 +179,16 @@ static void arm_cpu_reset(CPUState *s)
>      /* SVC mode with interrupts disabled.  */
>      env->uncached_cpsr = ARM_CPU_MODE_SVC;
>      env->daif = PSTATE_D | PSTATE_A | PSTATE_I | PSTATE_F;
> -    /* On ARMv7-M the CPSR_I is the value of the PRIMASK register, and is
> -     * clear at reset. Initial SP and PC are loaded from ROM.
> -     */
> +
>      if (arm_feature(env, ARM_FEATURE_M)) {
>          uint32_t initial_msp; /* Loaded from 0x0 */
>          uint32_t initial_pc; /* Loaded from 0x4 */
>          uint8_t *rom;
>
> -        env->daif &= ~PSTATE_I;
> +        /* For M profile we store FAULTMASK and PRIMASK in the
> +         * PSTATE F and I bits; these are both clear at reset.
> +         */
> +        env->daif &= ~(PSTATE_I | PSTATE_F);
>
>          /* The reset value of this bit is IMPDEF, but ARM recommends
>           * that it resets to 1, so QEMU always does that rather than making
> @@ -195,6 +196,7 @@ static void arm_cpu_reset(CPUState *s)
>           */
>          env->v7m.ccr = R_V7M_CCR_STKALIGN_MASK;
>
> +        /* Load the initial SP and PC from the vector table at address 0 */
>          rom = rom_ptr(0);
>          if (rom) {
>              /* Address zero is covered by ROM which hasn't yet been


--
Alex Bennée