Re: [Qemu-devel] [PATCH 18/32] ppc: Don't update NIP in DCR access routines

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Jul 27, 2016 at 08:21:12AM +1000, Benjamin Herrenschmidt wrote:
> This is no longer necessary as the helpers will properly retrieve
> the return address when needed

Well, the helpers are only fixed in this patch IIUC.

> 
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> ---
>  target-ppc/timebase_helper.c | 23 +++++++++++++----------
>  target-ppc/translate.c       | 12 ------------
>  2 files changed, 13 insertions(+), 22 deletions(-)
> 
> diff --git a/target-ppc/timebase_helper.c b/target-ppc/timebase_helper.c
> index a07faa4..73363e0 100644
> --- a/target-ppc/timebase_helper.c
> +++ b/target-ppc/timebase_helper.c
> @@ -19,6 +19,7 @@
>  #include "qemu/osdep.h"
>  #include "cpu.h"
>  #include "exec/helper-proto.h"
> +#include "exec/exec-all.h"
>  #include "qemu/log.h"
>  
>  /*****************************************************************************/
> @@ -143,15 +144,16 @@ target_ulong helper_load_dcr(CPUPPCState *env, target_ulong dcrn)
>  
>      if (unlikely(env->dcr_env == NULL)) {
>          qemu_log_mask(LOG_GUEST_ERROR, "No DCR environment\n");
> -        helper_raise_exception_err(env, POWERPC_EXCP_PROGRAM,
> -                                   POWERPC_EXCP_INVAL |
> -                                   POWERPC_EXCP_INVAL_INVAL);
> +        raise_exception_err_ra(env, POWERPC_EXCP_PROGRAM,
> +                               POWERPC_EXCP_INVAL |
> +                               POWERPC_EXCP_INVAL_INVAL, GETPC());
>      } else if (unlikely(ppc_dcr_read(env->dcr_env,
>                                       (uint32_t)dcrn, &val) != 0)) {
>          qemu_log_mask(LOG_GUEST_ERROR, "DCR read error %d %03x\n",
>                        (uint32_t)dcrn, (uint32_t)dcrn);
> -        helper_raise_exception_err(env, POWERPC_EXCP_PROGRAM,
> -                                   POWERPC_EXCP_INVAL | POWERPC_EXCP_PRIV_REG);
> +        raise_exception_err_ra(env, POWERPC_EXCP_PROGRAM,
> +                               POWERPC_EXCP_INVAL |
> +                               POWERPC_EXCP_PRIV_REG, GETPC());
>      }
>      return val;
>  }
> @@ -160,14 +162,15 @@ void helper_store_dcr(CPUPPCState *env, target_ulong dcrn, target_ulong val)
>  {
>      if (unlikely(env->dcr_env == NULL)) {
>          qemu_log_mask(LOG_GUEST_ERROR, "No DCR environment\n");
> -        helper_raise_exception_err(env, POWERPC_EXCP_PROGRAM,
> -                                   POWERPC_EXCP_INVAL |
> -                                   POWERPC_EXCP_INVAL_INVAL);
> +        raise_exception_err_ra(env, POWERPC_EXCP_PROGRAM,
> +                               POWERPC_EXCP_INVAL |
> +                               POWERPC_EXCP_INVAL_INVAL, GETPC());
>      } else if (unlikely(ppc_dcr_write(env->dcr_env, (uint32_t)dcrn,
>                                        (uint32_t)val) != 0)) {
>          qemu_log_mask(LOG_GUEST_ERROR, "DCR write error %d %03x\n",
>                        (uint32_t)dcrn, (uint32_t)dcrn);
> -        helper_raise_exception_err(env, POWERPC_EXCP_PROGRAM,
> -                                   POWERPC_EXCP_INVAL | POWERPC_EXCP_PRIV_REG);
> +        raise_exception_err_ra(env, POWERPC_EXCP_PROGRAM,
> +                               POWERPC_EXCP_INVAL |
> +                               POWERPC_EXCP_PRIV_REG, GETPC());
>      }
>  }
> diff --git a/target-ppc/translate.c b/target-ppc/translate.c
> index 84bcb09..f0e0ec6 100644
> --- a/target-ppc/translate.c
> +++ b/target-ppc/translate.c
> @@ -5262,8 +5262,6 @@ static void gen_mfdcr(DisasContext *ctx)
>      TCGv dcrn;
>  
>      CHK_SV;
> -    /* NIP cannot be restored if the memory exception comes from an helper */
> -    gen_update_nip(ctx, ctx->nip - 4);
>      dcrn = tcg_const_tl(SPR(ctx->opcode));
>      gen_helper_load_dcr(cpu_gpr[rD(ctx->opcode)], cpu_env, dcrn);
>      tcg_temp_free(dcrn);
> @@ -5279,8 +5277,6 @@ static void gen_mtdcr(DisasContext *ctx)
>      TCGv dcrn;
>  
>      CHK_SV;
> -    /* NIP cannot be restored if the memory exception comes from an helper */
> -    gen_update_nip(ctx, ctx->nip - 4);
>      dcrn = tcg_const_tl(SPR(ctx->opcode));
>      gen_helper_store_dcr(cpu_env, dcrn, cpu_gpr[rS(ctx->opcode)]);
>      tcg_temp_free(dcrn);
> @@ -5295,8 +5291,6 @@ static void gen_mfdcrx(DisasContext *ctx)
>      GEN_PRIV;
>  #else
>      CHK_SV;
> -    /* NIP cannot be restored if the memory exception comes from an helper */
> -    gen_update_nip(ctx, ctx->nip - 4);
>      gen_helper_load_dcr(cpu_gpr[rD(ctx->opcode)], cpu_env,
>                          cpu_gpr[rA(ctx->opcode)]);
>      /* Note: Rc update flag set leads to undefined state of Rc0 */
> @@ -5311,8 +5305,6 @@ static void gen_mtdcrx(DisasContext *ctx)
>      GEN_PRIV;
>  #else
>      CHK_SV;
> -    /* NIP cannot be restored if the memory exception comes from an helper */
> -    gen_update_nip(ctx, ctx->nip - 4);
>      gen_helper_store_dcr(cpu_env, cpu_gpr[rA(ctx->opcode)],
>                           cpu_gpr[rS(ctx->opcode)]);
>      /* Note: Rc update flag set leads to undefined state of Rc0 */
> @@ -5322,8 +5314,6 @@ static void gen_mtdcrx(DisasContext *ctx)
>  /* mfdcrux (PPC 460) : user-mode access to DCR */
>  static void gen_mfdcrux(DisasContext *ctx)
>  {
> -    /* NIP cannot be restored if the memory exception comes from an helper */
> -    gen_update_nip(ctx, ctx->nip - 4);
>      gen_helper_load_dcr(cpu_gpr[rD(ctx->opcode)], cpu_env,
>                          cpu_gpr[rA(ctx->opcode)]);
>      /* Note: Rc update flag set leads to undefined state of Rc0 */
> @@ -5332,8 +5322,6 @@ static void gen_mfdcrux(DisasContext *ctx)
>  /* mtdcrux (PPC 460) : user-mode access to DCR */
>  static void gen_mtdcrux(DisasContext *ctx)
>  {
> -    /* NIP cannot be restored if the memory exception comes from an helper */
> -    gen_update_nip(ctx, ctx->nip - 4);
>      gen_helper_store_dcr(cpu_env, cpu_gpr[rA(ctx->opcode)],
>                           cpu_gpr[rS(ctx->opcode)]);
>      /* Note: Rc update flag set leads to undefined state of Rc0 */

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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