Re: [Qemu-devel] [PATCH v3] target-arm: allow modifying vfp fpexc en bit only

[Laurent Desnogues <laurent.desnogues@gmail.com>]

On Mon, Oct 26, 2009 at 10:46 AM,  <juha.riihimaki@nokia.com> wrote:
> From: Juha Riihimäki <juha.riihimaki@nokia.com>
>
> All other bits except for the EN in the VFP FPEXC register are defined
> as subarchitecture specific and real functionality for any of the
> other bits has not been implemented in QEMU. However, current code
> allows modifying all bits in the VFP FPEXC register leading to
> problems when guest code is writing 1's to the subarchitecture
> specific bits and checking whether the bits stay up to verify the
> existence of functionality which in fact does not exist in QEMU.
> This patch has been revised to include the same behavior change in
> the gdb register write function.
>
> Signed-off-by: Juha Riihimäki <juha.riihimaki@nokia.com>

Acked-by: Laurent Desnogues <laurent.desnogues@gmail.com>


Laurent

> ---
>  target-arm/helper.c    |    2 +-
>  target-arm/translate.c |    3 +++
>  2 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/target-arm/helper.c b/target-arm/helper.c
> index 701629a..ee5df59 100644
> --- a/target-arm/helper.c
> +++ b/target-arm/helper.c
> @@ -233,7 +233,7 @@ static int vfp_gdb_set_reg(CPUState *env, uint8_t *buf, int reg)
>     switch (reg - nregs) {
>     case 0: env->vfp.xregs[ARM_VFP_FPSID] = ldl_p(buf); return 4;
>     case 1: env->vfp.xregs[ARM_VFP_FPSCR] = ldl_p(buf); return 4;
> -    case 2: env->vfp.xregs[ARM_VFP_FPEXC] = ldl_p(buf); return 4;
> +    case 2: env->vfp.xregs[ARM_VFP_FPEXC] = ldl_p(buf) & (1 << 30); return 4;
>     }
>     return 0;
>  }
> diff --git a/target-arm/translate.c b/target-arm/translate.c
> index 8503b92..d19ac7f 100644
> --- a/target-arm/translate.c
> +++ b/target-arm/translate.c
> @@ -2804,6 +2804,9 @@ static int disas_vfp_insn(CPUState * env, DisasContext *s, uint32_t insn)
>                         case ARM_VFP_FPEXC:
>                             if (IS_USER(s))
>                                 return 1;
> +                            /* TODO: VFP subarchitecture support.
> +                             * For now, keep the EN bit only */
> +                            tcg_gen_andi_i32(tmp, tmp, 1 << 30);
>                             store_cpu_field(tmp, vfp.xregs[rn]);
>                             gen_lookup_tb(s);
>                             break;
> --
> 1.6.5
>
>
>
>