Re: [Qemu-devel] [PATCH] target-arm: Implement FPEXC32_EL2 system register

["Edgar E. Iglesias" <edgar.iglesias@gmail.com>]

On Mon, Jan 18, 2016 at 03:53:34PM +0000, Peter Maydell wrote:
> The AArch64 FPEXC32_EL2 system register is visible at EL2 and EL3,
> and allows those exception levels to read and write the FPEXC
> register for a lower exception level that is using AArch32.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>


> ---
> ARM Trusted Firmware expects this to exist (as does your average
> hypervisor, I expect).
> 
>  target-arm/helper.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/target-arm/helper.c b/target-arm/helper.c
> index 196c111..e8ede3f 100644
> --- a/target-arm/helper.c
> +++ b/target-arm/helper.c
> @@ -2890,6 +2890,17 @@ static void sctlr_write(CPUARMState *env, const ARMCPRegInfo *ri,
>      tlb_flush(CPU(cpu), 1);
>  }
>  
> +static CPAccessResult fpexc32_access(CPUARMState *env, const ARMCPRegInfo *ri)
> +{
> +    if ((env->cp15.cptr_el[2] & CPTR_TFP) && arm_current_el(env) == 2) {
> +        return CP_ACCESS_TRAP_EL2;
> +    }
> +    if (env->cp15.cptr_el[3] & CPTR_TFP) {
> +        return CP_ACCESS_TRAP_EL3;
> +    }
> +    return CP_ACCESS_OK;
> +}
> +
>  static const ARMCPRegInfo v8_cp_reginfo[] = {
>      /* Minimal set of EL0-visible registers. This will need to be expanded
>       * significantly for system emulation of AArch64 CPUs.
> @@ -3150,6 +3161,11 @@ static const ARMCPRegInfo v8_cp_reginfo[] = {
>        .opc0 = 3, .opc1 = 0, .crn = 4, .crm = 2, .opc2 = 0,
>        .type = ARM_CP_NO_RAW,
>        .access = PL1_RW, .readfn = spsel_read, .writefn = spsel_write },
> +    { .name = "FPEXC32_EL2", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .opc1 = 4, .crn = 5, .crm = 3, .opc2 = 0,
> +      .type = ARM_CP_ALIAS,
> +      .fieldoffset = offsetof(CPUARMState, vfp.xregs[ARM_VFP_FPEXC]),
> +      .access = PL2_RW, .accessfn = fpexc32_access },
>      REGINFO_SENTINEL
>  };
>  
> -- 
> 1.9.1
>