Re: What's the correct way to implement rfi and related instruction.

[Cédric Le Goater]

> QEMU 5.2.x, an e300 based machine ppc603 are impacted.
> Here is my fix, narrowed down to  MSR_TGPR and  MSR_ILE
> ```
> From 42ce41671f1e6c4dd44e6fb481bbda9df09320bd Mon Sep 17 00:00:00 2001
> From: Yonggang Luo <luoyonggang@gmail.com <mailto:luoyonggang@gmail.com>>
> Date: Sun, 10 Jan 2021 00:08:00 -0800
> Subject: [PATCH] ppc: Fix rfi/rfid/hrfi/... emulation again
> 
> This revert part mask bits for ppc603/ppc4x that disabled in  
> a2e71b28e832346409efc795ecd1f0a2bcb705a3.
> Remove redundant macro MSR_BOOK3S_MASK.
> Fixes boot VxWorks on e300
> 
> Signed-off-by: Yonggang Luo <luoyonggang@gmail.com 
> <mailto:luoyonggang@gmail.com>>
> ---
>  target/ppc/excp_helper.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
> index 1c48b9fdf6..df70c5a4e8 100644
> --- a/target/ppc/excp_helper.c
> +++ b/target/ppc/excp_helper.c
> @@ -1156,8 +1156,10 @@ static inline void do_rfi(CPUPPCState *env, 
> target_ulong nip, target_ulong msr)
>  {
>      CPUState *cs = env_cpu(env);
>  
> -    /* MSR:POW cannot be set by any form of rfi */
> +    /* MSR:POW,TGPR,ILE cannot be set by any form of rfi */
>      msr &= ~(1ULL << MSR_POW);
> +    msr &= ~(1ULL << MSR_TGPR);

Indeed. The e300 user manual says that TGPR is cleared by rfi. We should 
add a per-cpu family mask and not a global setting.

> +    msr &= ~(1ULL << MSR_ILE);

that's curious. I am still trying to understand that part. May be this is 
due to the lack of HID2 modeling which contains a "True little-endian" bit.

Is your image Little endian ? 

C. 

>  
>  #if defined(TARGET_PPC64)
>      /* Switching to 32-bit ? Crop the nip */
> @@ -1190,7 +1192,6 @@ void helper_rfi(CPUPPCState *env)
>      do_rfi(env, env->spr[SPR_SRR0], env->spr[SPR_SRR1] & 0xfffffffful);
>  }
>  
> -#define MSR_BOOK3S_MASK
>  #if defined(TARGET_PPC64)
>  void helper_rfid(CPUPPCState *env)
>  {
> -- 
> 2.29.2.windows.3
> 
> ```
> 
> --
>          此致
> 礼
> 罗勇刚
> Yours
>     sincerely,
> Yonggang Luo