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Re: [PATCH v2] target/riscv: fix TB_FLAGS bits overlapping bug for rvv/r


From: Frank Chang
Subject: Re: [PATCH v2] target/riscv: fix TB_FLAGS bits overlapping bug for rvv/rvh
Date: Wed, 24 Feb 2021 08:43:48 +0800

On Wed, Feb 24, 2021 at 2:24 AM Richard Henderson <richard.henderson@linaro.org> wrote:
On 2/23/21 12:19 AM, frank.chang@sifive.com wrote:
> From: Frank Chang <frank.chang@sifive.com>
>
> TB_FLAGS mem_idx bits was extended from 2 bits to 3 bits in
> commit: c445593, but other TB_FLAGS bits for rvv and rvh were
> not shift as well so these bits may overlap with each other when
> rvv is enabled.
>
> Signed-off-by: Frank Chang <frank.chang@sifive.com>

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

> -#define TB_FLAGS_MMU_MASK   7
>  #define TB_FLAGS_PRIV_MMU_MASK                3
>  #define TB_FLAGS_PRIV_HYP_ACCESS_MASK   (1 << 2)
>  #define TB_FLAGS_MSTATUS_FS MSTATUS_FS
...
> +FIELD(TB_FLAGS, MEM_IDX, 0, 3)
> +FIELD(TB_FLAGS, VL_EQ_VLMAX, 3, 1)
> +FIELD(TB_FLAGS, LMUL, 4, 2)
> +FIELD(TB_FLAGS, SEW, 6, 3)
> +FIELD(TB_FLAGS, VILL, 9, 1)
>  /* Is a Hypervisor instruction load/store allowed? */
> -FIELD(TB_FLAGS, HLSX, 9, 1)
> +FIELD(TB_FLAGS, HLSX, 10, 1)

The only other thing that I'd add at this point is a comment about MSTATUS_FS
-- a 2-bit field at bit 13 -- for the benefit of the next person that adds
something to TB_FLAGS.


In fact, in RVV patchset, both MSTATUS_FS and MSTATUS_VS are skipped
and I also add the comments to state that.
The bits are also rearranged to fill the empty bit holes in RVV patchset on my local branch:

  FIELD(TB_FLAGS, MEM_IDX, 0, 3)
  FIELD(TB_FLAGS, LMUL, 3, 3)
  FIELD(TB_FLAGS, SEW, 6, 3)
  /* Skip MSTATUS_VS (0x600) bits */
  FIELD(TB_FLAGS, VL_EQ_VLMAX, 11, 1)
  FIELD(TB_FLAGS, VILL, 12, 1)
  /* Skip MSTATUS_FS (0x6000) bits */
  /* Is a Hypervisor instruction load/store allowed? */
  FIELD(TB_FLAGS, HLSX, 15, 1)

Thanks for the review.
Frank Chang
 

r~

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