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Re: [PATCH v2 06/55] target/microblaze: Do not set MO_ALIGN for user-onl


From: Edgar E. Iglesias
Subject: Re: [PATCH v2 06/55] target/microblaze: Do not set MO_ALIGN for user-only
Date: Wed, 4 Aug 2021 11:25:52 +0200

On Mon, Aug 02, 2021 at 06:13:54PM -1000, Richard Henderson wrote:
> The kernel will fix up unaligned accesses, so emulate that
> by allowing unaligned accesses to succeed.


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



> 
> Cc: Edgar E. Iglesias <edgar.iglesias@gmail.com>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  target/microblaze/translate.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/target/microblaze/translate.c b/target/microblaze/translate.c
> index a14ffed784..ef44bca2fd 100644
> --- a/target/microblaze/translate.c
> +++ b/target/microblaze/translate.c
> @@ -727,6 +727,7 @@ static TCGv compute_ldst_addr_ea(DisasContext *dc, int 
> ra, int rb)
>  }
>  #endif
>  
> +#ifndef CONFIG_USER_ONLY
>  static void record_unaligned_ess(DisasContext *dc, int rd,
>                                   MemOp size, bool store)
>  {
> @@ -739,6 +740,7 @@ static void record_unaligned_ess(DisasContext *dc, int rd,
>  
>      tcg_set_insn_start_param(dc->insn_start, 1, iflags);
>  }
> +#endif
>  
>  static bool do_load(DisasContext *dc, int rd, TCGv addr, MemOp mop,
>                      int mem_index, bool rev)
> @@ -760,12 +762,19 @@ static bool do_load(DisasContext *dc, int rd, TCGv 
> addr, MemOp mop,
>          }
>      }
>  
> +    /*
> +     * For system mode, enforce alignment if the cpu configuration
> +     * requires it.  For user-mode, the Linux kernel will have fixed up
> +     * any unaligned access, so emulate that by *not* setting MO_ALIGN.
> +     */
> +#ifndef CONFIG_USER_ONLY
>      if (size > MO_8 &&
>          (dc->tb_flags & MSR_EE) &&
>          dc->cfg->unaligned_exceptions) {
>          record_unaligned_ess(dc, rd, size, false);
>          mop |= MO_ALIGN;
>      }
> +#endif
>  
>      tcg_gen_qemu_ld_i32(reg_for_write(dc, rd), addr, mem_index, mop);
>  
> @@ -906,12 +915,19 @@ static bool do_store(DisasContext *dc, int rd, TCGv 
> addr, MemOp mop,
>          }
>      }
>  
> +    /*
> +     * For system mode, enforce alignment if the cpu configuration
> +     * requires it.  For user-mode, the Linux kernel will have fixed up
> +     * any unaligned access, so emulate that by *not* setting MO_ALIGN.
> +     */
> +#ifndef CONFIG_USER_ONLY
>      if (size > MO_8 &&
>          (dc->tb_flags & MSR_EE) &&
>          dc->cfg->unaligned_exceptions) {
>          record_unaligned_ess(dc, rd, size, true);
>          mop |= MO_ALIGN;
>      }
> +#endif
>  
>      tcg_gen_qemu_st_i32(reg_for_read(dc, rd), addr, mem_index, mop);
>  
> -- 
> 2.25.1
> 



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